User Defined Adjacency SID for ISIS or OSPF
This section provides an overview of user-defined Adjacency Segment Identifiers (Adj-SIDs) in Intermediate System to Intermediate System Segment Routing (ISIS-SR) or Open Shortest Path First (OSPF) environments.
SR is a modern forwarding paradigm that enables advanced traffic engineering (TE) by encoding path information within packet headers using segment identifiers (SIDs). SR-TE tunnels can be:
• Manually provisioned on the tunnel headend, or
• Dynamically computed and programmed by a centralized controller.
To implement SR-TE effectively, traffic must often be steered through specific nodes or links within the network:
• Prefix-SID is used to route traffic through a specific node.
• Adjacency SID (Adj-SID) enforces routing over a particular link.
Default Behavior
By default, IS-IS or OSPF dynamically allocates adjacency SIDs. These dynamic values:
• Are not persistent across reloads or process restarts.
• It cannot be predicted in advance.
• Require real-time IGP database access by controllers.
Due to these limitations, user-defined (static) adjacency SIDs are introduced to offer deterministic, persistent SID values, enabling efficient and controlled SR path computation.
Benefits
Implementing user-defined adjacency SIDs in IS-IS SR networks offers several advantages:
• Deterministic SID Allocation: users can assign fixed, known SIDs to specific links.
• Persistent Across Reloads: static SIDs retain its value even after reboots or process restarts.
• Controller-Friendly: simplifies path computation for external SDN controllers or SR orchestration.
• Improved Traffic Engineering: enables precise control of SR path selection across specific links.
• Simplified Troubleshooting: known SID values improve visibility and operational consistency.
OSPF Configuration
Configure OSPF with Segment Routing, assign user-defined Adj-SIDs to specific interfaces, and set up SR-TE tunnels from PE1 (headend) to PE2 (tailend) to enable deterministic traffic engineering across the core network.
Topology
This topology illustrates the OSPF Adj-SID feature in a SR-enabled network. It includes two Provider Edge (PE) routers, PE1 and PE2, connected through two redundant paths: P1 and P2, and via P3 and P4. By default, OSPF may install both paths as Equal-Cost Multi-paths (ECMP). To enforce traffic over a specific path, such as the route through P1 and P2, Adj-SIDs are assigned to the PE1–P1, P1–P2, and P2–PE2 links. PE1 can then insert these Adj-SIDs into the SR label stack, ensuring deterministic forwarding along the intended path. This mechanism allows precise traffic steering independent of IGP shortest-path decisions, enabling better traffic engineering, fast reroute, and SLA compliance.
L2VPN with SRLB-SID-ADJ configuration topology
The following steps describe to configure user-defined adjacency SIDs in an OSPF-SR environment for deterministic traffic engineering.
1. Enable Segment Routing to define the label blocks used for Prefix-SID and Adjacency-SID:
#configure terminal
(config)#segment-routing
(config-sr)#global block 10001 20000
(config-sr)#local block 100000 109999
2. Configure the loopback interface with a Prefix-SID to identify the router globally in the SR domain:
(config)#interface lo
(config -if)#ip address 43.43.43.43/32 secondary
(config -if)#prefix-sid index 4300
(config-if)#commit
(config-if)#exit
3. Configure LDP to ensure compatibility with non-SR MPLS devices and to maintain dual-protocol support:
(config)#router ldp
(config-router)#router-id 43.43.43.43
(config-router)#targeted-peer ipv4 14.14.14.14
(config-router-targeted-peer)#exit-targeted-peer-mode
(config-router)#transport-address ipv4 43.43.43.43
(config-router)#commit
(config-router)#exit
4. Configure the interfaces with an Adjacency SID using an absolute value to enable fine-grained control over the forwarding path:
(config)#interface ce3
(config-if)#ip address 16.0.0.10/24
(config-if)#adjacency-sid ospf absolute 100500
(config-if)#ip ospf network point-to-point
(config-if)#label-switching
(config-if)#enable-ldp ipv4
(config-if)#commit
(config-if)#exit
5. Configure the PO100 interface with an Adjacency SID using an index to assign a label from the local block dynamically:
(config)#interface po100
(config-if)#ip address 15.0.0.20/24
(config-if)#adjacency-sid ospf index 501
(config-if)#ip ospf network point-to-point
(config-if)#label-switching
(config-if)#enable-ldp ipv4
(config-if)#commit
(config-if)#exit
6. Create a port-channel to bundle physical interfaces and increase bandwidth and resiliency:
(config-if)#interface xe20
(config-if)#channel-group 100 mode active
(config-if)#exit
(config-if)#interface xe21
(config-if)#channel-group 100 mode active
(config-if)#exit
7. Configure OSPF with Segment Routing enabled to advertise SIDs through the IGP:
(config)#router ospf 100
(config-router)#ospf router-id 43.43.43.43
(config-router)#network 15.0.0.20/24 area 0
(config-router)#network 16.0.0.10/24 area 0
(config-router)#network 43.43.43.43/32 area 0
(config-router)#segment-routing mpls
(config-router)#commit
(config-router)#exit
8. Define an SR Policy to steer traffic dynamically based on constraints for traffic engineering:
(config)#tunnel-policy PE1-P1-PE2
(config-tnl-policy)# color 1
(config)#tunnel-policy PE1-P3-PE2
(config-tnl-policy)# color 2
(config)#segment-routing
(config-sr)# traffic-engineering
(config-sr-te) policy PE1-P1-PE2
(config-sr-pol) color 1 end-point 14.14.14.14
(config-sr-pol-cp) candidate-path 1
(config-sr-pol-cp)# dynamic-path ospf 1
(config-sr-pol-cp)# constraints
(config-sr-dyn-cp-cons)# 30.30.30.30 loose
(config-sr-dyn-cp-cons)# 44.44.44.44 loose
(config-sr-pol-cp)# exit-pol-cp
(config-sr-pol)#exit-sr-pol
9. Configure VRFs to define tenant-specific routing tables and isolate routing instances per service:
(config)#mac vrf vrf500
(config-vrf)#rd 43.43.43.43:500
(config-vrf)#route-target both 500:500
(config)#mac vrf vpls600
(config-vrf)#rd 43.43.43.43:600
(config-vrf)#route-target both 600:600
(config)#mac vrf vrfetree700
(config-vrf)#rd 101:1
(config-vrf)#route-target export 101:1
(config-vrf)#route-target import 102:1
10. Map VTEP to loopback IP to ensure loopback-reachability across the EVPN MPLS fabric:
(config-vrf)#evpn mpls vtep-ip-global 43.43.43.43
11. Configure EVPN instances for ELINE, ELAN, and ETREE services to enable L2 VPN delivery over MPLS using BGP-EVPN signaling:
(config)#evpn mpls id 2 xconnect target-mpls-id 252
and target identifier
(config)#host-reachability-protocol evpn-bgp vrf500
(config)#evpn mpls id 600
(config)#host-reachability-protocol evpn-bgp vpls600
(config)#evpn mpls id 700
(config)#host-reachability-protocol evpn-bgp vrfetree700
12. Configure BGP EVPN peering to advertise EVPN routes and establish control-plane reachability between PEs:
(config)#router bgp 100
(config-router)#bgp router-id 43.43.43.43
(config-router)#neighbor 14.14.14.14 remote-as 100
(config-router)#neighbor 14.14.14.14 update-source lo
(config-router)#address-family vpnv4 unicast
(config-router-af)#neighbor 14.14.14.14 activate
(config-router-af)#exit-address-family
(config-router)#address-family l2vpn evpn
(config-router-af)#neighbor 14.14.14.14 activate
(config-router-af)#exit-address-family
(config-router)#exit
13. Configure a VPLS instance to deliver Ethernet multipoint services using LDP-based signaling:
(config)#mpls vpls100 100
(config-vpls)#signaling ldp
(config-vpls-sig)#vpls-type ethernet
(config-vpls-sig)# vpls-peer 14.14.14.14 tunnel-select-policy PE1-P3-PE2
(config-vpls-sig)#exit-signaling
(config-vpls)#exit-vpls
14. Configure a VPWS instance to deliver point-to-point Ethernet services using SR policy as a tunnel selector:
(config)#mpls l2-circuit VPWS200 200 14.14.14.14
(config-pseudowire)# tunnel-select-policy PE1-P5-PE2
15. Configure BGP-signaled VPLS instance for enhanced scaling and control-plane signaling using BGP:
(config)#mpls vpls BGP-VPLS-PE1-PE2-300 300
(config-vpls)#signaling bgp
(config-vpls-sig)#ve-id 500
(config-vpls-sig)#exit-signaling
(config-vpls)#exit-vpls
16. Associate service instances to subinterfaces using Dot1Q encapsulation to map VLANs to specific L2VPN services:
(config-if)#interface xe17.100 switchport
(config-if)#encapsulation dot1q 100
(config-if)#access-if-vpls
(config-acc-if-vpls)#mpls-vpls vpls100
(config-if)#interface xe17.200 switchport
(config-if)#encapsulation dot1q 200
(config-if)#access-if-vpws
(config-acc-if-vpls)#mpls-vpws VPWS100
(config-if)#interface xe17.300 switchport
(config-if)#encapsulation dot1q 300
(config-if)#access-if-vpls
(config-acc-if-vpls)#mpls-vpls BGP-VPLS-PE1-PE2-300
(config-if)#interface xe17.500 switchport
(config-if)#encapsulation dot1q 500
(config-if)#access-if-evpn
(config-acc-if-vpls)#map vpn-id 2
(config-if)#interface xe17.600 switchport
(config-if)#encapsulation dot1q 600
(config-if)#access-if-evpn
(config-acc-if-vpls)#map vpn-id 600
(config-if)#interface xe17.700 switchport
(config-if)#encapsulation dot1q 700
(config-if)#access-if-evpn
(config-acc-if-vpls)#map vpn-id 700
(config-acc-if-vpls)#commit
(config-acc-if-vpls)#end
Configuration Snapshot
PE1
!
hostname PE1
!
interface Loopback0
ip address 43.43.43.43 255.255.255.255
!
interface ce3
ip address 16.0.0.10 255.255.255.0
ip ospf network point-to-point
mpls ip
mpls ldp enable
!
interface Port-channel100
ip address 15.0.0.20 255.255.255.0
ip ospf network point-to-point
mpls ip
mpls ldp enable
!
interface TenGigabitEthernet0/0/0
channel-group 100 mode active
!
interface TenGigabitEthernet0/0/1
channel-group 100 mode active
!
interface TenGigabitEthernet0/0/2.100
encapsulation dot1Q 100
xconnect vfi vpls100
!
interface TenGigabitEthernet0/0/2.200
encapsulation dot1Q 200
xconnect VPWS200
!
interface TenGigabitEthernet0/0/2.300
encapsulation dot1Q 300
xconnect vfi BGP-VPLS-PE1-PE2-300
!
interface TenGigabitEthernet0/0/2.500
encapsulation dot1Q 500
evpn
evpn instance 2
!
interface TenGigabitEthernet0/0/2.600
encapsulation dot1Q 600
evpn
evpn instance 600
!
interface TenGigabitEthernet0/0/2.700
encapsulation dot1Q 700
evpn
evpn instance 700
!
mpls label range 10001 20000
mpls ldp router-id Loopback0 force
mpls ldp
!
segment-routing
global block 10001 20000
local block 100000 109999
!
router ospf 100
router-id 43.43.43.43
network 15.0.0.0 0.0.0.255 area 0
network 16.0.0.0 0.0.0.255 area 0
network 43.43.43.43 0.0.0.0 area 0
segment-routing mpls
!
router bgp 100
bgp router-id 43.43.43.43
neighbor 14.14.14.14 remote-as 100
neighbor 14.14.14.14 update-source Loopback0
!
address-family vpnv4
neighbor 14.14.14.14 activate
exit-address-family
!
address-family l2vpn evpn
neighbor 14.14.14.14 activate
exit-address-family
!
l2vpn vfi context vpls100
vpn id 100
bridge-domain 100
autodiscovery ldp
neighbor 14.14.14.14
!
l2vpn vfi context BGP-VPLS-PE1-PE2-300
vpn id 300
bridge-domain 300
autodiscovery bgp
ve-id 500
!
l2vpn xconnect context VPWS200
vpn id 200
neighbor 14.14.14.14
!
evpn
vtep ip 43.43.43.43
!
evpn instance 2
rd 43.43.43.43:500
route-target import 500:500
route-target export 500:500
!
evpn instance 600
rd 43.43.43.43:600
route-target import 600:600
route-target export 600:600
!
evpn instance 700
rd 101:1
route-target import 102:1
route-target export 101:1
!
P1
segment-routing
global block 10001 20000
local block 30000 36000
!
interface lo
ip address 5.5.5.5 255.255.255.255 secondary
prefix-sid index 3000
!
router ldp
router-id 5.5.5.5
!
interface ce4
ip address 16.0.0.20 255.255.255.0
label-switching
ip ospf network point-to-point
adjacency-sid ospf index 1000
!
interface Po400
ip address 17.0.0.10 255.255.255.0
label-switching
ip ospf network point-to-point
adjacency-sid ospf absolute 30700
!
interface ce22
channel-group 400 mode active
!
interface ce23
channel-group 400 mode active
!
router ospf 100
router-id 5.5.5.5
network 17.0.0.0 0.0.0.255 area 0
network 16.0.0.0 0.0.0.255 area 0
network 5.5.5.5 0.0.0.0 area 0
segment-routing mpls
!
P2
!segment-routing
global block 10001 20000
local block 41000 50000
!
interface lo
ip address 44.44.44.44 255.255.255.255 secondary
prefix-sid index 4400
!
router ldp
router-id 44.44.44.44
!
interface sa300
ip address 12.0.0.10 255.255.255.0
label-switching
ip ospf network point-to-point
adjacency-sid ospf index 45000
!
interface Po400
ip address 17.0.0.20 255.255.255.0
label-switching
ip ospf network point-to-point
adjacency-sid ospf index 2000
!
interface ce50
channel-group 400 mode active
!
interface ce51
channel-group 400 mode active
!
interface xe21
static-channel-group 300
!
interface xe22
static-channel-group 300
!
router ospf 100
router-id 5.5.5.5
network 17.0.0.0 0.0.0.255 area 0
network 16.0.0.0 0.0.0.255 area 0
network 5.5.5.5 0.0.0.0 area 0
segment-routing mpls
!
P3
segment-routing
global block 10001 17000
local block 41000 50000
!
interface lo
ip address 42.42.42.42 255.255.255.255 secondary
prefix-sid index 4200
!
router ldp
router-id 42.42.42.42
!
interface Po100
ip address 15.0.0.10 255.255.255.0
label-switching
ip ospf network point-to-point
adjacency-sid ospf index 4159
!
interface xe9
ip address 14.0.0.10 255.255.255.0
label-switching
ip ospf network point-to-point
adjacency-sid ospf absolute 41599
!
interface xe20
channel-group 100 mode active
!
interface xe21
channel-group 100 mode active
!
router ospf 100
router-id 42.42.42.42
network 14.0.0.0 0.0.0.255 area 0
network 15.0.0.0 0.0.0.255 area 0
network 42.42.42.42 0.0.0.0 area 0
segment-routing mpls
!
P4
segment-routing
global block 10001 20000
local block 41000 50000
!
interface lo
ip address 29.29.29.29 255.255.255.255 secondary
prefix-sid index 2900
!
router ldp
router-id 29.29.29.29
!
interface xe2.2000
ip address 13.0.0.20 255.255.255.0
label-switching
ip ospf network point-to-point
adjacency-sid ospf index 4900
!
interface xe9
ip address 14.0.0.20 255.255.255.0
label-switching
ip ospf network point-to-point
adjacency-sid ospf index 5000
!
router ospf 100
router-id 5.5.5.5
network 13.0.0.0 0.0.0.255 area 0
network 14.0.0.0 0.0.0.255 area 0
network 29.29.29.29 0.0.0.0 area 0
segment-routing mpls
!
PE2
segment-routing
global block 10001 20000
local block 65000 74000
!
interface lo
ip address 14.14.14.14 255.255.255.255 secondary
prefix-sid index 1400
!
router ldp
router-id 14.14.14.14
targeted-peer ipv4 43.43.43.43
transport-address ipv4 14.14.14.14
!
interface sa300
ip address 12.0.0.10 255.255.255.0
adjacency-sid ospf index 5000
ip ospf network point-to-point
label-switching
enable-ldp ipv4
!
interface x2.2000
ip address 13.0.0.10 255.255.255.0
adjacency-sid ospf index 5001
ip ospf network point-to-point
label-switching
enable-ldp ipv4
!
interface xe3
static-channel-group 300
!
interface xe4
channel-group 100 mode active
!
router ospf 100
router-id 14.14.14.14
network 12.0.0.0 0.0.0.255 area 0
network 13.0.0.0 0.0.0.255 area 0
network 14.14.14.14 0.0.0.0 area 0
segment-routing mpls
!
tunnel-policy PE1-P1-PE2
color 1
!
tunnel-policy PE1-P3-PE2
color 2
!
segment-routing
traffic-engineering
policy PE1-P1-PE2
color 1 end-point 43.43.43.43
candidate-path 1
dynamic-path ospf 1
constraints
44.44.44.44 loose
30.30.30.30 loose
!
segment-routing
traffic-engineering
policy PE1-P3-PE2
color 2 end-point 43.43.43.43
candidate-path 1
dynamic-path ospf 1
constraints
29.29.29.29 loose
42.42.42.42 loose
!
mac vrf vrf500
rd 14.14.14.14:500
route-target both 500:500
!
mac vrf vpls600
rd 14.14.14.14:600
route-target both 600:600
!
mac vrf vrfetree700
rd 101:1
route-target export 101:1
route-target import 102:1
evpn mpls vtep-ip-global 14.14.14.14
!
evpn mpls id 252 xconnect target-mpls-id 2
!
host-reachability-protocol evpn-bgp vrf500
!
evpn mpls id 600
!
host-reachability-protocol evpn-bgp vpls600
!
evpn mpls id 700
!
host-reachability-protocol evpn-bgp vrfetree700
!
router bgp 100
bgp router-id 14.14.14.14
neighbor 43.43.43.43 remote-as 100
neighbor 43.43.43.43 update-source lo
address-family vpnv4 unicast
neighbor 43.43.43.43 activate
exit-address-family
address-family l2vpn evpn
neighbor 43.43.43.43 activate
exit-address-family
!
mpls vpls100 100
signaling ldp
vpls-type ethernet
vpls-peer 43.43.43.43 tunnel-select-policy PE1-P3-PE2
!
mpls l2-circuit VPWS200 200 43.43.43.43
tunnel-select-policy PE1-P5-PE2
!
mpls vpls BGP-VPLS-PE1-PE2-300 300
signaling bgp
ve-id 500
!
interface xe17.100 switchport
encapsulation dot1q 100
access-if-vpls
mpls-vpls vpls100
!
interface xe17.200 switchport
encapsulation dot1q 200
access-if-vpws
mpls-vpws VPWS100
!
interface xe17.300 switchport
encapsulation dot1q 300
access-if-vpls
mpls-vpls BGP-VPLS-PE1-PE2-300
!
interface xe17.500 switchport
encapsulation dot1q 500
access-if-evpn
map vpn-id 252
!
interface xe17.600 switchport
encapsulation dot1q 600
access-if-evpn
map vpn-id 600
!
interface xe17.700 switchport
encapsulation dot1q 700
access-if-evpn
map vpn-id 700
!
Validation
PE1
SRLB-PE1-7043#show ip ospf neighbor detail
Neighbor 42.42.42.42, interface address 15.0.0.10
In the area 0.0.0.0 via interface po100
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:34
Neighbor is detected for 00:20:31
Neighbor is FULL for 00:20:31
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 27521
Static adj sid: 100501
Bidirectional Forwarding Detection is enabled
Neighbor 5.5.5.5, interface address 16.0.0.20
In the area 0.0.0.0 via interface ce3
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:33
Neighbor is detected for 00:28:15
Neighbor is FULL for 00:28:15
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 27520
Static adj sid: 100500
Bidirectional Forwarding Detection is enabled
SRLB-PE1-7043#show mpls ilm-table
Codes: > - installed ILM, * - selected ILM, p - stale ILM
K - CLI ILM, T - MPLS-TP, s - Stitched ILM
S - SNMP, L - LDP, R - RSVP, C - CRLDP
B - BGP , K - CLI , V - LDP_VC, I - IGP_SHORTCUT
O - OSPF/OSPF6 SR, i - ISIS SR, k - SR CLI
P - SR Policy, U - unknown
LDP ilm-ecmp - disabled
Code FEC/VRF/L2CKT ILM-ID In-Label Out-Label In-Intf Out-Intf/VRF Nexthop pri LSP-Type
O> 5.5.5.5/32 10 19000 3 N/A ce3 16.0.0.20 Yes LSP_DEFAULT
B> evpn:600 2 640 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:600 3 17 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:2 1 16 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:900 7 19 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:700 5 18 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:1000 8 20 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:900 6 642 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:700 4 641 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
O> 14.14.14.14/32 13 17400 17400 N/A po100 15.0.0.10 Yes LSP_DEFAULT
O> 29.29.29.29/32 14 18900 18900 N/A po100 15.0.0.10 Yes LSP_DEFAULT
P> 5.5.5.5/32 11 26883 3 N/A ce3 16.0.0.20 Yes LSP_DEFAULT
B> vrf400 16 25664 Nolabel N/A vrf400 N/A Yes LSP_DEFAULT
O> 44.44.44.44/32 12 20400 14401 N/A ce3 16.0.0.20 Yes LSP_DEFAULT
O> 42.42.42.42/32 19 20200 3 N/A po100 15.0.0.10 Yes LSP_DEFAULT
P> 14.14.14.14/32 15 26882 14401 N/A ce3 16.0.0.20 Yes LSP_DEFAULT
P> 14.14.14.14/32 21 26881 18900 N/A po100 15.0.0.10 Yes LSP_DEFAULT
O> 16.0.0.20/32 18 100500 3 N/A ce3 16.0.0.20 Yes LSP_DEFAULT
O> 16.0.0.20/32 9 27520 3 N/A ce3 16.0.0.20 Yes LSP_DEFAULT
O> 15.0.0.10/32 20 27521 3 N/A po100 15.0.0.10 Yes LSP_DEFAULT
V> l2ckt:200 17 26240 Nolabel ce3 xe17.200 N/A Yes LSP_DEFAULT
O> 15.0.0.10/32 27 100501 3 N/A po100 15.0.0.10 Yes LSP_DEFAULT
SRLB-PE1-7043#show mpls label-space 0
Label range (min - max) : 16 - 1048575
module-static
Default range : 16 - 14079
module-srlb
Default range (Usable) : 14080 - 15999
Default range (Allotted) : 14080 - 15999
module-srgb
Default range (Usable) : 16000 - 23999
Default range (Allotted) : 16000 - 24319
module-rsvp
Configured range : N/A
Current dynamic range : N/A
module-ldp
Configured range : Not configured
Current dynamic range : 26240 - 26879
module-bgp
Configured range : Not configured
Current dynamic range : 25600 - 26239
module-isis-srlb
Configured range : N/A
Current dynamic range : 26880 - 27519
module-ospf-srlb
Configured range : N/A
Current dynamic range : 27520 - 28159
SRLB-PE1-7043#
P1
SRLB-P1-7030#show ip ospf neighbor detail
Neighbor 43.43.43.43, interface address 16.0.0.10
In the area 0.0.0.0 via interface ce4
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:30
Neighbor is detected for 00:29:51
Neighbor is FULL for 00:29:51
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 26240
Static adj sid: 31000
Bidirectional Forwarding Detection is enabled
Neighbor 44.44.44.44, interface address 17.0.0.20
In the area 0.0.0.0 via interface po400
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:37
Neighbor is detected for 00:28:35
Neighbor is FULL for 00:28:26
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 26241
Static adj sid: 30700
Bidirectional Forwarding Detection is enabled
SRLB-P1-7030#show mpls ilm-table
Codes: > - installed ILM, * - selected ILM, p - stale ILM
K - CLI ILM, T - MPLS-TP, s - Stitched ILM
S - SNMP, L - LDP, R - RSVP, C - CRLDP
B - BGP , K - CLI , V - LDP_VC, I - IGP_SHORTCUT
O - OSPF/OSPF6 SR, i - ISIS SR, k - SR CLI
P - SR Policy, U - unknown
LDP ilm-ecmp - disabled
Code FEC/VRF/L2CKT ILM-ID In-Label Out-Label In-Intf Out-Intf/VRF Nexthop pri LSP-Type
O> 16.0.0.10/32 1 26240 3 N/A ce4 16.0.0.10 Yes LSP_DEFAULT
O> 43.43.43.43/32 3 14301 3 N/A ce4 16.0.0.10 Yes LSP_DEFAULT
O> 29.29.29.29/32 9 12901 18900 N/A ce4 16.0.0.10 Yes LSP_DEFAULT
O> 14.14.14.14/32 8 11401 11401 N/A po400 17.0.0.20 Yes LSP_DEFAULT
O> 42.42.42.42/32 10 14201 20200 N/A ce4 16.0.0.10 Yes LSP_DEFAULT
O> 44.44.44.44/32 7 14401 3 N/A po400 17.0.0.20 Yes LSP_DEFAULT
P> 43.43.43.43/32 4 25600 3 N/A ce4 16.0.0.10 Yes LSP_DEFAULT
O> 17.0.0.20/32 6 30700 3 N/A po400 17.0.0.20 Yes LSP_DEFAULT
O> 17.0.0.20/32 5 26241 3 N/A po400 17.0.0.20 Yes LSP_DEFAULT
O> 16.0.0.10/32 2 31000 3 N/A ce4 16.0.0.10 Yes LSP_DEFAULT
SRLB-P1-7030#show mpls label-space 0
Label range (min - max) : 16 - 1048575
module-static
Default range : 16 - 14079
module-srlb
Default range (Usable) : 14080 - 15999
Default range (Allotted) : 14080 - 15999
module-srgb
Default range (Usable) : 16000 - 23999
Default range (Allotted) : 16000 - 24319
module-rsvp
Configured range : N/A
Current dynamic range : N/A
module-ldp
Configured range : N/A
Current dynamic range : N/A
module-bgp
Configured range : N/A
Current dynamic range : N/A
module-isis-srlb
Configured range : N/A
Current dynamic range : 25600 - 26239
module-ospf-srlb
Configured range : N/A
Current dynamic range : 26240 - 26879
SRLB-P1-7030#
P2
---
SRLB-P2-7044#show ip ospf neighbor detail
Neighbor 14.14.14.14, interface address 12.0.0.20
In the area 0.0.0.0 via interface sa300
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:38
Neighbor is detected for 00:28:44
Neighbor is FULL for 00:28:35
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 26240
Static adj sid: 45000
Bidirectional Forwarding Detection is enabled
Neighbor 5.5.5.5, interface address 17.0.0.10
In the area 0.0.0.0 via interface po400
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:31
Neighbor is detected for 00:28:41
Neighbor is FULL for 00:28:32
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 26241
Static adj sid: 43000
Bidirectional Forwarding Detection is enabled
SRLB-P2-7044#show mpls ilm-table
Codes: > - installed ILM, * - selected ILM, p - stale ILM
K - CLI ILM, T - MPLS-TP, s - Stitched ILM
S - SNMP, L - LDP, R - RSVP, C - CRLDP
B - BGP , K - CLI , V - LDP_VC, I - IGP_SHORTCUT
O - OSPF/OSPF6 SR, i - ISIS SR, k - SR CLI
P - SR Policy, U - unknown
LDP ilm-ecmp - disabled
Code FEC/VRF/L2CKT ILM-ID In-Label Out-Label In-Intf Out-Intf/VRF Nexthop pri LSP-Type
O> 5.5.5.5/32 8 13001 3 N/A po400 17.0.0.10 Yes LSP_DEFAULT
B> evpn:2000 3 641 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:900 2 640 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:900 1 16 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
O> 29.29.29.29/32 7 12901 12901 N/A sa300 12.0.0.20 Yes LSP_DEFAULT
O> 14.14.14.14/32 6 11401 3 N/A sa300 12.0.0.20 Yes LSP_DEFAULT
O> 12.0.0.20/32 4 26240 3 N/A sa300 12.0.0.20 Yes LSP_DEFAULT
O> 43.43.43.43/32 9 14301 14301 N/A po400 17.0.0.10 Yes LSP_DEFAULT
O> 42.42.42.42/32 11 14201 14201 N/A sa300 12.0.0.20 Yes LSP_DEFAULT
O> 17.0.0.10/32 12 43000 3 N/A po400 17.0.0.10 Yes LSP_DEFAULT
O> 17.0.0.10/32 5 26241 3 N/A po400 17.0.0.10 Yes LSP_DEFAULT
O> 12.0.0.20/32 10 45000 3 N/A sa300 12.0.0.20 Yes LSP_DEFAULT
SRLB-P2-7044#show mpls label-space 0
Label range (min - max) : 16 - 1048575
module-static
Default range : 16 - 14079
module-srlb
Default range : 14080 - 15999
Configured range : 41000 - 50000
module-srgb
Default range : 16000 - 23999
Configured range : 10001 - 20000
module-rsvp
Configured range : N/A
Current dynamic range : N/A
module-ldp
Configured range : N/A
Current dynamic range : N/A
module-bgp
Configured range : Not configured
Current dynamic range : 25600 - 26239
module-ospf-srlb
Configured range : N/A
Current dynamic range : 26240 - 26879
SRLB-P2-7044#!
P3
SRLB-P3-7042#show ip ospf neighbor detail
Neighbor 29.29.29.29, interface address 14.0.0.20
In the area 0.0.0.0 via interface xe9
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:39
Neighbor is detected for 00:22:20
Neighbor is FULL for 00:22:20
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 25601
Static adj sid: 41599
Bidirectional Forwarding Detection is enabled
Neighbor 43.43.43.43, interface address 15.0.0.20
In the area 0.0.0.0 via interface po100
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:37
Neighbor is detected for 00:22:27
Neighbor is FULL for 00:22:17
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 25600
Static adj sid: 45159
Bidirectional Forwarding Detection is enabled
SRLB-P3-7042#show mpls ilm-table
Codes: > - installed ILM, * - selected ILM, p - stale ILM
K - CLI ILM, T - MPLS-TP, s - Stitched ILM
S - SNMP, L - LDP, R - RSVP, C - CRLDP
B - BGP , K - CLI , V - LDP_VC, I - IGP_SHORTCUT
O - OSPF/OSPF6 SR, i - ISIS SR, k - SR CLI
P - SR Policy, U - unknown
LDP ilm-ecmp - disabled
Code FEC/VRF/L2CKT ILM-ID In-Label Out-Label In-Intf Out-Intf/VRF Nexthop pri LSP-Type
O> 5.5.5.5/32 2 19000 19000 N/A po100 15.0.0.20 Yes LSP_DEFAULT
O> 29.29.29.29/32 4 18900 3 N/A xe9 14.0.0.20 Yes LSP_DEFAULT
O> 14.14.14.14/32 3 17400 11401 N/A xe9 14.0.0.20 Yes LSP_DEFAULT
O> 14.0.0.20/32 1 25601 3 N/A xe9 14.0.0.20 Yes LSP_DEFAULT
O> 44.44.44.44/32 6 20400 14401 N/A xe9 14.0.0.20 Yes LSP_DEFAULT
O> 43.43.43.43/32 5 20300 3 N/A po100 15.0.0.20 Yes LSP_DEFAULT
O> 15.0.0.20/32 7 25600 3 N/A po100 15.0.0.20 Yes LSP_DEFAULT
O> 14.0.0.20/32 8 41599 3 N/A xe9 14.0.0.20 Yes LSP_DEFAULT
O> 15.0.0.20/32 9 45159 3 N/A po100 15.0.0.20 Yes LSP_DEFAULT
SRLB-P3-7042#show mpls label-space 0
Label range (min - max) : 16 - 1048575
module-static
Default range : 16 - 14079
module-srlb
Default range (Usable) : 14080 - 15999
Default range (Allotted) : 14080 - 15999
module-srgb
Default range (Usable) : 16000 - 23999
Default range (Allotted) : 16000 - 24319
module-rsvp
Configured range : N/A
Current dynamic range : N/A
module-ldp
Configured range : N/A
Current dynamic range : N/A
module-bgp
Configured range : N/A
Current dynamic range : N/A
module-ospf-srlb
Configured range : N/A
Current dynamic range : 25600 - 26239
SRLB-P3-7042#!
P4
SRLB-P4-7029#show ip ospf neighbor detail
Neighbor 14.14.14.14, interface address 13.0.0.10
In the area 0.0.0.0 via interface xe2.2000
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:35
Neighbor is detected for 00:33:03
Neighbor is FULL for 00:32:55
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 26240
Static adj sid: 45900
Bidirectional Forwarding Detection is enabled
Neighbor 42.42.42.42, interface address 14.0.0.10
In the area 0.0.0.0 via interface xe9
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:34
Neighbor is detected for 00:22:33
Neighbor is FULL for 00:22:23
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 26241
Static adj sid: 46000
Bidirectional Forwarding Detection is enabled
SRLB-P4-7029#show mpls ilm-table
Codes: > - installed ILM, * - selected ILM, p - stale ILM
K - CLI ILM, T - MPLS-TP, s - Stitched ILM
S - SNMP, L - LDP, R - RSVP, C - CRLDP
B - BGP , K - CLI , V - LDP_VC, I - IGP_SHORTCUT
O - OSPF/OSPF6 SR, i - ISIS SR, k - SR CLI
P - SR Policy, U - unknown
LDP ilm-ecmp - disabled
Code FEC/VRF/L2CKT ILM-ID In-Label Out-Label In-Intf Out-Intf/VRF Nexthop pri LSP-Type
O> 44.44.44.44/32 7 14401 14401 N/A xe2.2000 13.0.0.10 Yes LSP_DEFAULT
O> 14.14.14.14/32 5 11401 3 N/A xe2.2000 13.0.0.10 Yes LSP_DEFAULT
B> evpn:900 2 640 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:900 1 16 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:2000 3 641 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
O> 42.42.42.42/32 12 14201 3 N/A xe9 14.0.0.10 Yes LSP_DEFAULT
O> 5.5.5.5/32 8 13001 13001 N/A xe2.2000 13.0.0.10 Yes LSP_DEFAULT
O> 43.43.43.43/32 9 14301 20300 N/A xe9 14.0.0.10 Yes LSP_DEFAULT
O> 13.0.0.10/32 6 45900 3 N/A xe2.2000 13.0.0.10 Yes LSP_DEFAULT
O> 13.0.0.10/32 4 26240 3 N/A xe2.2000 13.0.0.10 Yes LSP_DEFAULT
O> 14.0.0.10/32 10 26241 3 N/A xe9 14.0.0.10 Yes LSP_DEFAULT
O> 14.0.0.10/32 11 46000 3 N/A xe9 14.0.0.10 Yes LSP_DEFAULT
SRLB-P4-7029#show mpls label-space 0
Label range (min - max) : 16 - 1048575
module-static
Default range : 16 - 14079
module-srlb
Default range : 14080 - 15999
Configured range : 41000 - 50000
module-srgb
Default range : 16000 - 23999
Configured range : 10001 - 20000
module-rsvp
Configured range : N/A
Current dynamic range : N/A
module-ldp
Configured range : N/A
Current dynamic range : N/A
module-bgp
Configured range : Not configured
Current dynamic range : 25600 - 26239
module-ospf-srlb
Configured range : N/A
Current dynamic range : 26240 - 26879
SRLB-P4-7029#!
PE2
SRLB-PE2-7014#show ip ospf neighbor detail
Neighbor 44.44.44.44, interface address 12.0.0.10
In the area 0.0.0.0 via interface sa300
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:39
Neighbor is detected for 00:28:45
Neighbor is FULL for 00:28:45
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 27521
Static adj sid: 70000
Bidirectional Forwarding Detection is enabled
Neighbor 29.29.29.29, interface address 13.0.0.20
In the area 0.0.0.0 via interface xe2.2000
Neighbor priority is 1, State is Full, 5 state changes
DR is 0.0.0.0, BDR is 0.0.0.0
Options is 0x42 (-|O|-|-|-|-|E|-)
Dead timer due in 00:00:37
Neighbor is detected for 00:32:58
Neighbor is FULL for 00:32:58
Database Summary List 0
Link State Request List 0
Link State Retransmission List 0
Crypt Sequence Number is 0
Thread Inactivity Timer on
Thread Database Description Retransmission off
Thread Link State Request Retransmission off
Thread Link State Update Retransmission off
System assigned adj sid: 27520
Static adj sid: 70001
Bidirectional Forwarding Detection is enabled
SRLB-PE2-7014#show mpls ilm-table
Codes: > - installed ILM, * - selected ILM, p - stale ILM
K - CLI ILM, T - MPLS-TP, s - Stitched ILM
S - SNMP, L - LDP, R - RSVP, C - CRLDP
B - BGP , K - CLI , V - LDP_VC, I - IGP_SHORTCUT
O - OSPF/OSPF6 SR, i - ISIS SR, k - SR CLI
P - SR Policy, U - unknown
LDP ilm-ecmp - disabled
Code FEC/VRF/L2CKT ILM-ID In-Label Out-Label In-Intf Out-Intf/VRF Nexthop pri LSP-Type
O> 29.29.29.29/32 7 12901 3 N/A xe2.2000 13.0.0.20 Yes LSP_DEFAULT
B> evpn:600 2 640 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:600 3 17 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:252 1 16 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:700 5 18 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
B> evpn:700 4 641 Nolabel N/A N/A 127.0.0.1 Yes LSP_DEFAULT
O> 13.0.0.20/32 6 27520 3 N/A xe2.2000 13.0.0.20 Yes LSP_DEFAULT
O> 44.44.44.44/32 9 14401 3 N/A sa300 12.0.0.10 Yes LSP_DEFAULT
O> 42.42.42.42/32 17 14201 14201 N/A xe2.2000 13.0.0.20 Yes LSP_DEFAULT
O> 5.5.5.5/32 10 13001 13001 N/A sa300 12.0.0.10 Yes LSP_DEFAULT
O> 43.43.43.43/32 11 14301 14301 N/A sa300 12.0.0.10 Yes LSP_DEFAULT
P> 43.43.43.43/32 18 26881 14201 N/A xe2.2000 13.0.0.20 Yes LSP_DEFAULT
B> vrf400 12 25664 Nolabel N/A vrf400 N/A Yes LSP_DEFAULT
P> 43.43.43.43/32 13 26882 13001 N/A sa300 12.0.0.10 Yes LSP_DEFAULT
O> 12.0.0.10/32 15 70000 3 N/A sa300 12.0.0.10 Yes LSP_DEFAULT
O> 12.0.0.10/32 8 27521 3 N/A sa300 12.0.0.10 Yes LSP_DEFAULT
V> l2ckt:200 14 26240 Nolabel sa300 xe17.200 N/A Yes LSP_DEFAULT
O> 13.0.0.20/32 16 70001 3 N/A xe2.2000 13.0.0.20 Yes LSP_DEFAULT
SRLB-PE2-7014#show mpls label-space 0
Label range (min - max) : 16 - 1048575
Label range (min - max) : 16 - 1048575
module-static
Default range : 16 - 14079
module-srlb
Default range (Usable) : 14080 - 15999
Default range (Allotted) : 14080 - 15999
module-srgb
Default range (Usable) : 16000 - 23999
Default range (Allotted) : 16000 - 24319
module-rsvp
Configured range : N/A
Current dynamic range : N/A
+ module-ldp
Configured range : Not configured
Current dynamic range : 26240 - 26879
module-bgp
Configured range : Not configured
Current dynamic range : 25600 - 26239
module-isis-srlb
Configured range : N/A
Current dynamic range : 26880 - 27519
module-ospf-srlb
Configured range : N/A
Current dynamic range : 27520 - 28159
ISIS Configuration
Configure IS-IS with Segment Routing, assign user-defined Adj-SIDs to specific interfaces, and set up SR-TE tunnels from PE1 (headend) to PE2 (tailend) to enable deterministic traffic engineering across the core network.
Topology
This topology illustrates Segment Routing with IS-IS using Adjacency SIDs for precise traffic engineering. R1 (PE1) and R3 (PE2) are service endpoints, with traffic flowing from CE1 to CE2.
R1 connects to R2 and R4, while R3 connects to R2, R5, and CE2. R2, R4, R5, and R6 form the SR-MPLS core, enabling multiple path options. R5 plays a central role, connecting with all core routers, including an aggregated link (Port-Channel 10) to R2.
Adjacency SIDs are assigned to point-to-point links like R1–R2, R2–R3, and R5–R3. These locally significant SIDs allow traffic to be explicitly routed through specific links. For example, traffic from CE1 to CE2 can be steered via R1 → R2 → R5 → R3 using a mix of Node and Adj-SIDs, bypassing shortest-path routing.
L2VPN with SRLB-SID-ADJ Configuration Topology
The following steps describe to configure user-defined adjacency SIDs in an IS-IS-SR environment for deterministic traffic engineering.
1. Define the Segment Routing Local Block (SRLB) as the local SID range (42000–47000) for index-based static SID allocation.
#configure terminal
(config)#segment-routing
(config-sr)#local block 42000 47000
2. Assign a user-defined adjacency SID on an interface using either an absolute SID or an index-based method. Absolute assignment sets a fixed SID value explicitly, while index-based assignment calculates the SID by adding the index to the SRLB base.
• Absolute SID: Directly configure a fixed SID on the interface. For example, adjacency-sid isis absolute 42151 assigns SID 42151 to interface xe9, suitable for centrally managed environments.
(config)# interface xe9
(config-if)#adjacency-sid isis absolute 42151
• Index-Based SID: Configure an index value that, when added to the SRLB base, forms the SID. For instance, adjacency-sid isis index 14 on interface xe7.101 results in SID 42014 assuming an SRLB base of 42000.
(config)# interface xe7.101
(config-if)# adjacency-sid isis index 14
Configuration Snapshot
R1
qos enable
!
mpls ilm-ecmp sr
mpls ftn-ecmp sr
!
admin-group blue 1
!
tunnel-policy TP1
color 61
!
tunnel-policy TP2
color 102
!
!
ip vrf management
!
ip vrf VPN101
tunnel-select-policy TP1
rd 70000:100
route-target both 100:100
!
segment-routing
local block 42000 47000
traffic-engineering
segment-list SID_LIST_BSID_1
index 1 segment-type-1 42151
index 2 segment-type-1 26024
index 3 segment-type-1 70045
index 4 segment-type-1 555
exit-sr-sl
!
policy T123
color 101 end-point 3.3.3.3
candidate-path 1
dynamic-path isis 1
constraints
10.10.12.2 strict
10.10.23.3 strict
exit-cp-cons
!
exit-pol-cp
!
exit-sr-pol
!
policy T1245_bsid_563
color 61 end-point 3.3.3.3
candidate-path 1
explicit segment-list SID_LIST_BSID_1
exit-pol-cp
!
candidate-path 2
preference 80
dynamic-path isis 1
constraints
affinity include-all blue
exit-cp-cons
!
exit-pol-cp
!
exit-sr-pol
!
s-bfd sr policy T1245_bsid_563
!
s-bfd discriminator 1.1.1.1
!
interface lo
ip address 127.0.0.1/8
ip address 1.1.1.1/32 secondary
ipv6 address ::1/128
prefix-sid index 101 no-php
ip router isis 1
!
interface xe2
speed 10g
mtu 9216
!
interface xe2.101
encapsulation dot1q 101
load-interval 30
ip vrf forwarding VPN101
ip address 100.7.1.1/24
ipv6 address 101::1/64
mtu 9216
!
interface xe7
speed 10g
mtu 9216
!
interface xe7.101
encapsulation dot1q 14
ip address 10.10.14.1/24
label-switching
admin-group blue
adjacency-sid isis index 14
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
enable-ldp ipv4
!
interface xe9
speed 10g
load-interval 30
ip address 10.10.12.1/24
mtu 9216
label-switching
extended-admin-group blue
adjacency-sid isis absolute 42151
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
!
router isis 1
is-type level-2-only
metric-style wide
mpls traffic-eng router-id 1.1.1.1
mpls traffic-eng level-2
capability cspf
dynamic-hostname
fast-reroute ti-lfa level-1 proto ipv4
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0001.0000.0000.0001.00
passive-interface lo
isis segment-routing global block 16000 19000
segment-routing mpls
!
router bgp 70000
bgp router-id 1.1.1.1
neighbor 3.3.3.3 remote-as 70000
neighbor 3.3.3.3 update-source lo
!
address-family vpnv4 unicast
neighbor 3.3.3.3 activate
exit-address-family
!
address-family vpnv6 unicast
neighbor 3.3.3.3 activate
exit-address-family
!
address-family ipv4 vrf VPN101
redistribute connected
neighbor 100.7.1.2 remote-as 200
neighbor 100.7.1.2 activate
exit-address-family
!
address-family ipv6 vrf VPN101
redistribute connected
neighbor 101::2 remote-as 200
neighbor 101::2 activate
exit-address-family
!
exit
!
end
R2
qos enable
!
mpls ilm-ecmp sr
mpls ftn-ecmp sr
!
hostname DUT2
!
ip vrf management
!
segment-routing
local block 26000 30000
!
interface ce0
load-interval 30
ip address 10.10.25.2/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
!
interface lo
ip address 127.0.0.1/8
ip address 2.2.2.2/32 secondary
ipv6 address ::1/128
prefix-sid index 201 no-php
ip router isis 1
!
interface xe0
load-interval 30
ip address 10.10.24.2/24
mtu 9216
label-switching
adjacency-sid isis index 24
isis network point-to-point
ip router isis 1
!
interface xe1
ip address 10.10.26.2/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
!
interface xe6
load-interval 30
ip address 10.10.12.2/24
ip address 10.10.21.2/24 secondary
ip address 10.10.31.2/24 secondary
mtu 9216
label-switching
adjacency-sid isis index 21
isis network point-to-point
ip router isis 1
!
interface xe7
load-interval 30
ip address 10.10.23.2/24
mtu 9216
label-switching
adjacency-sid isis index 222
adjacency-sid ospf absolute 26022
isis network point-to-point
ip router isis 1
!
router isis 1
is-type level-2-only
metric-style wide
mpls traffic-eng router-id 2.2.2.2
mpls traffic-eng level-2
capability cspf
dynamic-hostname
fast-reroute ti-lfa level-1 proto ipv4
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0001.0000.0000.0022.00
passive-interface lo
isis segment-routing global block 16000 19000
segment-routing entropy-label
segment-routing mpls
!
end
R3
!
qos enable
!
mpls ilm-ecmp sr
mpls ftn-ecmp sr
!
hostname DUT3
port ce0 breakout 4X10g
!
tunnel-policy TP1
color 101
!
ip vrf VPN101
tunnel-select-policy TP1
rd 70000:100
route-target both 100:100
!
segment-routing
local block 30000 35000
traffic-engineering
policy T321
color 101 end-point 1.1.1.1
candidate-path 1
dynamic-path isis 1
constraints
10.10.23.2 strict
10.10.12.1 strict
exit-cp-cons
!
exit-pol-cp
!
exit-sr-pol
!
exit-te
!
s-bfd sr policy T321
!
s-bfd discriminator 3.3.3.3
!
!
interface po10
load-interval 30
ip address 10.10.35.3/24
mtu 9216
label-switching
adjacency-sid isis index 35
isis network point-to-point
ip router isis 1
!
interface sa1
!
interface ce0/1
channel-group 10 mode active
!
interface ce0/2
channel-group 10 mode active
!
interface lo
ip address 127.0.0.1/8
ip address 3.3.3.3/32 secondary
ipv6 address ::1/128
prefix-sid index 301 no-php
ip router isis 1
!
interface xe3
speed 10g
!
interface xe3.101
encapsulation dot1q 101
load-interval 30
ip vrf forwarding VPN101
ip address 100.8.1.1/24
ipv6 address 201::1/64
!
interface xe4
speed 10g
load-interval 30
ip address 10.10.36.3/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
!
interface xe5
speed 10g
load-interval 30
ip address 10.10.23.3/24
mtu 9216
label-switching
adjacency-sid isis index 32
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
!
router isis 1
is-type level-1-2
metric-style wide
mpls traffic-eng router-id 3.3.3.3
mpls traffic-eng level-1
mpls traffic-eng level-2
capability cspf
dynamic-hostname
fast-reroute ti-lfa level-1 proto ipv4
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0001.0000.0000.0002.00
passive-interface lo
isis segment-routing global block 16000 19000
segment-routing mpls
!
router bgp 70000
bgp router-id 3.3.3.3
neighbor 1.1.1.1 remote-as 70000
neighbor 1.1.1.1 update-source lo
neighbor 3001::2 remote-as 400
!
address-family vpnv4 unicast
neighbor 1.1.1.1 activate
exit-address-family
!
address-family vpnv6 unicast
neighbor 1.1.1.1 activate
exit-address-family
!
address-family ipv4 vrf VPN101
redistribute connected
neighbor 100.8.1.2 remote-as 100
neighbor 100.8.1.2 activate
exit-address-family
!
address-family ipv6 vrf VPN101
redistribute connected
neighbor 201::2 remote-as 100
neighbor 201::2 activate
exit-address-family
!
exit
!
end
R4
!
qos enable
!
mpls ilm-ecmp sr
mpls ftn-ecmp sr
!
hostname DUT4
admin-group blue 1
!
segment-routing
global block 65000 69000
local block 70000 75000
!
interface ce0
speed 40g
ip address 10.10.45.4/24
mtu 9216
label-switching
admin-group blue
adjacency-sid isis index 45
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
isis wide-metric 5
!
interface lo
ip address 127.0.0.1/8
ip address 4.4.4.4/32 secondary
ipv6 address ::1/128
prefix-sid index 401 no-php
ip router isis 1
!
interface xe0
load-interval 30
ip address 10.10.24.4/24
mtu 9216
label-switching
adjacency-sid isis index 42
isis network point-to-point
ip router isis 1
!
interface xe5
!
interface xe5.101
encapsulation dot1q 14
ip address 10.10.14.4/24
label-switching
adjacency-sid isis absolute 72101
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
!
router isis 1
is-type level-2-only
metric-style wide
mpls traffic-eng router-id 4.4.4.4
mpls traffic-eng level-2
capability cspf
dynamic-hostname
fast-reroute ti-lfa level-1 proto ipv4
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0001.0000.0000.0044.00
passive-interface lo
isis segment-routing global block 65000 65800
segment-routing entropy-label
segment-routing mpls
!
end
R5
!
qos enable
!
mpls ilm-ecmp sr
mpls ftn-ecmp sr
!
hostname DUT5
port ce15 breakout 4X10g
port ce16 breakout 4X10g
admin-group blue 1
!
segment-routing
local block 40000 48000
!
interface po10
load-interval 30
ip address 10.10.35.5/24
mtu 9216
label-switching
admin-group blue
adjacency-sid isis absolute 40124
isis network point-to-point
ip router isis 1
!
interface sa1
!
interface sa50
load-interval 30
ip address 10.10.65.5/24
mtu 9216
label-switching
adjacency-sid isis index 110
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
isis wide-metric 5
!
interface ce0
!
interface ce1
!
interface ce2
speed 40g
load-interval 30
ip address 10.10.45.5/24
mtu 9216
label-switching
adjacency-sid isis index 54
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
!
interface ce14
load-interval 30
ip address 10.10.25.5/24
mtu 9216
label-switching
adjacency-sid isis index 52
isis network point-to-point
ip router isis 1
!
interface ce15/1
ip address 10.10.56.5/24
mtu 9216
label-switching
admin-group blue
adjacency-sid isis index 56
shutdown
isis network point-to-point
ip router isis 1
!
interface ce15/2
static-channel-group 50
!
interface ce15/3
static-channel-group 50
!
interface ce15/4
ip address 10.56.56.5/24
mtu 9216
label-switching
admin-group blue
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
isis wide-metric 5
!
interface ce16/1
channel-group 10 mode active
!
interface ce16/2
channel-group 10 mode active
!
interface ce16/3
!
interface ce16/4
!
interface lo
ip address 127.0.0.1/8
ip address 5.5.5.5/32 secondary
ipv6 address ::1/128
prefix-sid index 501 no-php
ip router isis 1
!
exit
!
router isis 1
is-type level-1-2
metric-style wide
mpls traffic-eng router-id 5.5.5.5
mpls traffic-eng level-1
mpls traffic-eng level-2
capability cspf
dynamic-hostname
fast-reroute ti-lfa level-1 proto ipv4
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0001.0000.0000.0055.00
redistribute isis level-2 into level-1
passive-interface lo
isis segment-routing global block 16000 19000
segment-routing entropy-label
segment-routing mpls
!
end
R6
!
qos enable
!
mpls ilm-ecmp sr
mpls ftn-ecmp sr
!
hostname DUT6
port ce54 breakout 4X10g
admin-group blue 1
!
segment-routing
local block 30000 35000
!
interface sa50
load-interval 30
ip address 10.10.65.6/24
mtu 9216
label-switching
adjacency-sid isis absolute 30010
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
!
interface ce54/1
ip address 10.10.56.6/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
!
interface ce54/2
static-channel-group 50
!
interface ce54/3
static-channel-group 50
!
interface ce54/4
ip address 10.56.56.6/24
mtu 9216
label-switching
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
!
interface lo
ip address 127.0.0.1/8
ip address 6.6.6.6/32 secondary
ipv6 address ::1/128
prefix-sid index 601 no-php
ip router isis 1
!
interface xe2
ip address 10.10.26.6/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
!
interface xe4
ip address 10.10.36.6/24
mtu 9216
label-switching
admin-group blue
adjacency-sid isis absolute 35000
ip ospf network point-to-point
isis network point-to-point
ip router isis 1
!
router isis 1
is-type level-1-only
metric-style wide
mpls traffic-eng router-id 6.6.6.6
mpls traffic-eng level-2
dynamic-hostname
fast-reroute ti-lfa level-1 proto ipv4
bfd all-interfaces
net 49.0001.0000.0000.0066.00
passive-interface lo
isis segment-routing global block 16000 19000
segment-routing entropy-label
segment-routing mpls
!
end
Validation
To verify the configured adjacency SIDs and their advertisement status:
PE1#show clns neighbors xe9 detail
Tag 1: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
DUT2 xe9 80a2.355b.7008 Up 24 L2 IS-IS
Adjacency ID: 1
Uptime: 1d01h53m
Area Address(es): 49.0001
IP Address(es): 10.10.12.2 10.10.21.2 10.10.31.2
Level-2 Protocols Supported: IPv4
IPV4 Bidirectional Forwarding Detection is enabled
Adjacency advertisement: Advertise
Adjacency SID: 28161, ILM ID: 18
Static Adjacency SID: 42151, ILM ID: 19
Bypass trunk ID: 2201,
PQ-router ID: 4.4.4.4
PE1#show mpls ilm-table 10.10.12.2/32
Codes: > - installed ILM, * - selected ILM, p - stale ILM, ! - using backup
K - CLI ILM, T - MPLS-TP, s - Stitched ILM
S - SNMP, L - LDP, R - RSVP, C - CRLDP
B - BGP , K - CLI , V - LDP_VC, I - IGP_SHORTCUT
O - OSPF/OSPF6 SR, i - ISIS SR, k - SR CLI
P - SR Policy, U - unknown, UPStr - upstream
ILM-ECMP LDP: Disabled, SR: Enabled
Code FEC/VRF/L2CKT ILM-ID In-Label Out-Label In-Intf Out-Intf/VRF Nexthop pri Algo-Num UpTime UPStr peers
i> 10.10.12.2/32 18 28161 3 N/A xe9 10.10.12.2 Yes 0 1d01h53m
28161 65201 N/A xe7.101 10.10.14.4 No - -
i> 10.10.12.2/32 19 42151 3 N/A xe9 10.10.12.2 Yes 0 1d01h53m
42151 65201 N/A xe7.101 10.10.14.4 No - -
PE1#show isis database verbose PE1.00-00
Tag 1: VRF : default
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
DUT1.00-00 * 0x0000006D 0x587B 681 0/0/0
Area Address: 49.0001
NLPID: 0xCC
Hostname: DUT1
IP Address: 10.10.14.1
Router ID: 1.1.1.1
Router Cap: 1.1.1.1
Maximum SID Depth:
Entropy Readable Label Depth : 10
SRGB Range: 3001 SRGB Base SID: 16000 I:1 V:0
SR-Algorithms:
Algorithm: SPF
SBFD Discriminator: 1.1.1.1
Metric: 10 IS-Extended DUT4.00
Admin-Group:
Group 1
IPv4 Interface Address: 10.10.14.1
Neighbor IP Address: 10.10.14.4
Maximum Link Bandwidth : 10000000.00 kbits/sec
Reservable Bandwidth : 10000000.00 kbits/sec
Unreserved Bandwidth:
Unreserved Bandwidth at priority 0: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 1: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 2: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 3: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 4: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 5: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 6: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 7: 10000000.00 kbits/sec
TE-Default Metric: 10
Adjacency SID: 28160 F:0 B:0 V:1 L:1 S:0 P:0
Adjacency SID: 42014 F:0 B:0 V:1 L:1 S:0 P:1
Metric: 10 IS-Extended DUT2.00
IPv4 Interface Address: 10.10.12.1
Neighbor IP Address: 10.10.12.2
Maximum Link Bandwidth : 10000000.00 kbits/sec
Reservable Bandwidth : 10000000.00 kbits/sec
Unreserved Bandwidth:
Unreserved Bandwidth at priority 0: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 1: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 2: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 3: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 4: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 5: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 6: 10000000.00 kbits/sec
Unreserved Bandwidth at priority 7: 10000000.00 kbits/sec
TE-Default Metric: 10
Extended Administrative Group Bits (96):
(35)
Adjacency SID: 28161 F:0 B:0 V:1 L:1 S:0 P:0
Adjacency SID: 42151 F:0 B:0 V:1 L:1 S:0 P:1
Metric: 0 IP-Extended 1.1.1.1/32
Prefix-SID: index 101, Algorithm: SPF, R:0 N:1 P:1 E:0 V:0 L:0
Prefix Attribute Flags[0]: ELC Set
Metric: 10 IP-Extended 10.10.14.0/24
Prefix Attribute Flags[0]: ELC Set
Metric: 10 IP-Extended 10.10.12.0/24
Prefix Attribute Flags[0]: ELC Set
PE1#show isis segment-routing capability
Tag 1 Segment-Routing:
-----------------------------------------------------
Advertisement Router Capability :1.1.1.1
Algorithm0 :0
SRMS Preference :0
Total SID'S Supported :3001
SR ERLD :10
SID Range List Count :1
SID's Range :16000 - 19000
Total SID's Supported (SRLB) :0
SRLB Range List Count :0
-----------------------------------------------------
Advertisement Router Capability :2.2.2.2
Algorithm0 :0
SRMS Preference :0
Total SID'S Supported :3001
SR ERLD :6
SID Range List Count :1
SID's Range :16000 - 19000
Total SID's Supported (SRLB) :0
SRLB Range List Count :0
-----------------------------------------------------
Advertisement Router Capability :3.3.3.3
Algorithm0 :0
SRMS Preference :0
Total SID'S Supported :3001
SR ERLD :10
SID Range List Count :1
SID's Range :16000 - 19000
Total SID's Supported (SRLB) :0
SRLB Range List Count :0
-----------------------------------------------------
Advertisement Router Capability :4.4.4.4
Algorithm0 :0
SRMS Preference :0
Total SID'S Supported :801
SR ERLD :6
SID Range List Count :1
SID's Range :65000 - 65800
Total SID's Supported (SRLB) :0
SRLB Range List Count :0
-----------------------------------------------------
Advertisement Router Capability :5.5.5.5
Algorithm0 :0
SRMS Preference :0
Total SID'S Supported :3001
SR ERLD :10
SID Range List Count :1
SID's Range :16000 - 19000
Total SID's Supported (SRLB) :0
SRLB Range List Count :0
-----------------------------------------------------
Advertisement Router Capability :6.6.6.6
Algorithm0 :0
SRMS Preference :0
Total SID'S Supported :3001
SR ERLD :6
SID Range List Count :1
SID's Range :16000 - 19000
Total SID's Supported (SRLB) :0
SRLB Range List Count :0
PE1#show segment-routing policy T123
Policy-Name: T123 Color 101 End-point 3.3.3.3 Tunnel-ID: 2
Admin-Status: UP Oper-Status: UP for 03:41:23
State Transition Count: 11
CSPF Retry Limit: 100 CSPF Retry Interval: 10
Colored Service-FTN Dependent Count: 0
Binding SID :
BSID: 27526
Alloc mode: Dynamic
Oper State: Programmed
CP ID: 1, Active
Preference: 100 Path Type: Dynamic(isis) CP Origin: Local
CP state: Valid
Segment List:
Total no. of segments: 2
Segment0[LABEL]: Label :42151
Segment1[LABEL]: Label :26222
Out-if: xe9 Out-label-stack: 3/26222
Computed TE Metric: 20
Attributes:
Configured:
SID-Algorithm: 0
Affinity:
Metric-type: TE
IP Constraints: 10.10.12.2 strict
10.10.23.3 strict
Last Recorded Error: Route Not Found, 03:41:34 ago
Implementation Example
• Explicit Path Control in SR-TE Policies.
In an SR-MPLS environment, controllers (like an SDN orchestrator or PCE) require deterministic SIDs to build and enforce SR-TE paths. User-defined Adjacency SIDs ensure the SID values assigned to specific links are predictable and persistent, enabling the controller to push exact path instructions across the network.