TILFA for ISIS SR with Flexible Algorithms
Overview
Topology Independent Loop-Free Alternate (TI-LFA) for IS-IS Segment Routing (SR) with Flexible Algorithm (Flex-Algo) provides fast reroute protection (FRR), minimizes downtime, and provides re-convergence on failure detection.
Feature Characteristics
• IS-IS supports per-algorithm TI-LFA backup path calculation.
• TI-LFA backup path calculation for the default SPF algorithm is supported.
• TI-LFA path computation for flex-algos is based on constraint matching against the TE attributes of nodes and links.
• Backup path computation adheres to the same constraints as the primary path. These constraints are defined by the winner node of the flex-algo typically the node with the highest priority, or the highest router ID if multiple nodes have the same priority value.
• HSL is programmed with primary and backup LSP's for each specific flex-algo.
Benefits
This feature offers several key advantages:
• Sub-50ms Fast Reroute (FRR): Rapid recovery from link or node failures with precomputed backup paths.
• Algorithm-Aware Protection: Backup paths adhere to Flex-Algo constraints, enabling per-service or class-based protection.
• Prefix-Independent Backup: A single backup path protects multiple prefixes, reducing processing overhead.
• Constraint-Based Traffic Engineering: Ensures TE policies (For example: low latency, disjoint paths) are preserved during failures.
• Service Differentiation: Supports multiple algorithms tailored for specific application needs.
• Simplified Scalability: Avoids per-flow state and RSVP-TE complexity, enabling scalable, policy-driven routing.
Limitations
• Supports ISIS enhancements for Flexible Algorithms.
• Traffic Engineering and Segment Routing configurations must be enabled to advertise sub-TLVs.
• Dynamic SR-Policy creation based on Flex-Algo ID for path calculation is not supported in this release.
• Flexible Algorithm paths are not compatible with LDP-to-SR stitching. SR paths calculated using delay as a metric will not interwork with LDP paths calculated using IGP metrics.
• Router capability advertisements containing FAD TLVs require SR to be configured. LDP-only domains without SR cannot participate in Flex-Algo computations.
• IGP-based micro-loop avoidance is currently limited to Default Algorithm paths.
• BGP-LS extensions for Flex-Algo are not supported.
• Flexible Algorithm-specific IS-IS Adjacency Segment extensions are not supported.
• A maximum of eight Flexible Algorithms is supported.
• Fallback to the Default Algorithm is not supported.
Prerequisites
The TI-LFA for IS-IS Segment Routing with Flex-Algo feature can be enabled on OcNOS devices that meet the following requirements:
• Support for IS-IS Segment Routing with Flex-Algo, Equal-Cost Multi-Path (ECMP), and TI-LFA.
• Support for BGP-based services, including VPLS, L3VPN, and 6VPE.
• Support for EVPN services.
Configuration
The following configuration enables TILFA for ISIS-SR with Flex-Algo.
Topology
The topology consists of six routers configured to validate the TI-LFA feature for fast reroute protection in an SR-MPLS network.
• RTR1 and RTR3 serve as Provider Edge (PE) routers and are the primary devices under test.
• RTR2, RTR4, and RTR6 function primarily as core (P) routers, forwarding traffic through the network.
• RTR5 is a hybrid node acting both as a core router and as a Route Reflector (RR) for control-plane scalability.
The network includes diverse interconnections across the core, providing multiple Equal-Cost Multi-Path (ECMP) and non-ECMP paths. This setup enables the evaluation of TI-LFA behavior under various failure scenarios, including link and node failures, and ensures that backup paths are precomputed and meet the sub-50ms convergence requirement.
Logical Topologies Based on Flexible Algorithms
To configure Flex Algo functionality on nodes with ISIS as IGP, follow the steps mentioned below:
1. Configure loop-back interfaces.
• Access interface configuration mode for the loopback interface (interface loopback1).
• Assign an IPv4 address to the loopback interface using the IPv4 address command followed by the desired
• IPv4 address and subnet mask (ip address 25.0.0.1/32).
• Assign appropriate prefix-sid index for the loopback interface (prefix-sid index 1 no-php).
• Assign appropriate prefix-sid index for flex algorithm for the same loopback interface
• Configure IS-IS for IPv4 on the loopback interface using the ip router isis command, specifying the IS-IS process ID (ip router isis 1).
RTR1(config)#interface loopback2
RTR1(config-if)# ip address 25.0.1.1/32 secondary
RTR1(config-if)# prefix-sid index 1
RTR1(config-if)# prefix-sid algorithm-num 128 index 1281
RTR1(config-if)# prefix-sid algorithm-num 129 index 1291
RTR1(config-if)# ip router isis 1
RTR1(config-if)# exit
Details of loopbacks
Router | Role | Loopbacks | loopback IP | Node SID | ALGO SID |
|---|---|---|---|---|---|
RTR1 | PE | Loopback1 | 25.0.0.1/32 | NA | NA |
Loopback2 | 25.0.1.1/32 | 1 | Algo 128: 1281 Algo 129: 1291 | ||
RTR2 | P | Loopback1 | 25.0.1.1/32 | NA | NA |
Loopback2 | 25.0.0.2/32 | 2 | Algo 128: 1282 Algo 129: 1292 | ||
RTR3 | PE | Loopback1 | 25.0.1.2/32 | NA | NA |
Loopback2 | 25.0.0.3/32 | 3 | Algo 128: 1283 Algo 129: 1293 | ||
RTR4 | P | Loopback1 | 25.0.0.4/32 | NA | NA |
Loopback2 | 25.0.1.4/32 | 4 | Algo 128: 1284 Algo 129: 1294 | ||
RTR5 | P,RR | Loopback1 | 25.0.0.5/32 | NA | NA |
Loopback2 | 25.0.1.5/32 | 5 | Algo 128: 1285 Algo 129: 1295 | ||
RTR6 | P | Loopback1 | 25.0.0.6/32 | NA | NA |
Loopback2 | 25.0.1.6/32 | 6 | Algo 128: 1286 Algo 129: 1296 |
1. Configure network interface.
• Access interface configuration mode for the desired network interface (xe5, xe15 and xe22).
• Assign an IPv4 address to the network interface using the ipv4 address command followed by the desired
• IPv4 address and subnet mask (ip address 11.0.12.1/24).
• Configure the MTU for the interface (mtu 9216).
• Configure IS-IS for IPv4 on the interface using the IP router ISIS command, specifying the IS-IS process ID (ip router isis 1).
RTR1(config)#interface xe5
RTR1(config-if)# 11.0.12.1/24
RTR1(config-if)# mtu 9216
RTR1(config-if)# label-switching
RTR1(config-if)# ip router isis 1
RTR1(config-if)#exit
2. IS-IS and SR configuration.
• Configure I-IS metrics. Default IGP metric = 10.
• Configure IS-IS Level2 with wide metrics on all routers.
• Enable Segment Routing on all the routers.
• Advertise one Node-SID per router linked to loopback2 as described in the loopback addressing section.
• Configure new SRGB/SRLB range as follows:
RTR1(config)#segment-routing
RTR1(config-sr)# global block 20000 80000
Here additional details on IS-IS parameters:
• Remaining LSP lifetime = 65535 seconds
• LSP refresh (if configurable) = 65000 seconds
• LSP general interval = 1
• SPF interval exp 50 5000
RTR1(config)#router isis 1
RTR1(config-router)#is-type level-2-only
RTR1(config-router)#ignore-lsp-errors
RTR1(config-router)#lsp-gen-interval 1
RTR1(config-router)#max-lsp-lifetime 65535
RTR1(config-router)#spf-interval-exp 50 5000
RTR1(config-router)#metric-style wide
RTR1(config-router)#mpls traffic-eng router-id 25.0.1.1
RTR1(config-router)#mpls traffic-eng level-2
RTR1(config-router)#dynamic-hostname
RTR1(config-router)#net 49.0000.0100.0000.1011.00
RTR1(config-router)#isis segment-routing global block 20000 80000
RTR1(config-router)#segment-routing mpls
RTR1(config-router)#exit
3. Flex Algo Configuration:
All routers will be configured with the following algorithms:
• Algorithm 0: This uses standard SPF based on IGP metrics.
• Default IGP metric: 10
• Algorithm 128: Designed to minimize TE metrics and include all links.
• Algorithm 129: Optimized for minimizing delay metrics and includes all links.
• Delay metrics will be configured, and to ensure predictability, they may be static or dynamic depending on the test scenario.
RTR1(config)#router isis 1
RTR1(config-router)# capability flex-algo routing
RTR1(config-router)# flex-algo 128
RTR1(config-isis-fa)# metric-type te-metric
RTR1(config-isis-fa)# exit-flex-algo
RTR1(config-router)#exit
RTR1(config)#router isis 1
RTR1(config-router)# flex-algo 129
RTR1(config-isis-fa)# metric-type link-delay
RTR1(config-isis-fa)# exit-flex-algo
Link Attributes:
• Admin-Group Red: Assigned to bit position 1.
• Extended Admin-Group Green: Assigned to bit position 32
• Extended Admin-Group Blue: Assigned to bit position 93
• Te-metric as metric-type
• Link-delay as metric-type
RTR1(config)#
RTR1(config)#admin-group red 1
RTR1(config)#extended-admin-group green 32
RTR1(config)#extended-admin-group blue 93
RTR1(config)#int xe5
RTR1(config-if)# isis extended-admin-group flex-algo green
RTR1(config-if)# isis extended-admin-group flex-algo blue
RTR1(config-if)# isis te-metric flex-algo ipv4 225
RTR1(config-if)# isis te-minimum-delay flex-algo 10
RTR1(config-if)# isis te-maximum-delay flex-algo 20
RTR1(config-if)#exit
Flex-Algo Definition Advertisement:
• RTR2 acts as the primary node, advertising the Flex-Algo definition with a priority of 131.
• RTR5 serves as the backup node, advertising the Flex-Algo definition with a priority of 130.
RTR2(config-router)# flex-algo 128
RTR2(config-isis-fa)# priority 131
RTR2(config-isis-fa)# affinity-eag-include-any green
RTR2(config-isis-fa)# affinity-ag-exclude-any red
RTR2(config-isis-fa)# exit-flex-algo
RTR2(config-router)# flex-algo 129
RTR2(config-isis-fa)# priority 131
RTR2(config-isis-fa)# affinity-eag-include-all blue
RTR2(config-isis-fa)# affinity-ag-exclude-any orange
RTR2(config-isis-fa)# exit-flex-algo
4. Enable TILFA for Flex-Algo 0, 128, and 129:
RTR2(config)#router isis 1
RTR2(config-router)#fast-reroute ti-lfa level-2 proto ipv4
RTR2(config-router)#flex-algo 128
RTR2(config-isis-fa)#ti-lfa
RTR2(config-isis-fa)#exit
RTR2(config-router)#flex-algo 129
RTR2(config-isis-fa)#ti-lfa
RTR2(config-isis-fa)#exit
Below are derived logical Topologies Based on Flexible Algorithms:
IGP Metric-Based Topology Algorithm 0: Default IGP Metric-Based Topology
• This topology adheres to the SPF computation using standard IGP metrics.
• The default IGP metric is as 10, unless explicitly modified.
• Logical representation: All routers and links contribute to a baseline network topology designed for general-purpose traffic forwarding.
• Use case: Ideal for non-critical, general traffic with no constraints or considerations.
Flex Algo Zero
Algorithm 128: TE Metric-Optimized Topology (Minimizing TE Metrics)
• Focuses on traffic engineering metrics and considers all links when computing paths.
• Logical topology is created based on configured TE metrics.
• Constraints for flex-algo 128 are Links with EAG GREEN are included links with AG RED are excluded.
• Example: Below scenario where specific links marked with a Green affinity are exclusively utilized to manage high-throughput services. All Red links are excluded.
FlexAlgo 128Algorithm 129: Delay Metric-Optimized Topology (Minimizing Delay)
• Constructs a topology optimized for minimizing delay metrics.
• Delay metrics are either dynamically monitored or configured statically to ensure test consistency.
• Logical paths are computed using the lowest cumulative delay across links, ensuring an efficient flow of delay-sensitive traffic.
• Constraints for flex-algo 129 are Links with EAG BLUE are included and links with AG ORANGE are excluded
• TWAMP is configured Between RTR1, RTR5, and RTR3 (forward direction) and static link-delay is configured in the reverse direction (RTR3, RTR5, and RTR1).
• Use case: Ideal for low-latency traffic flows, such as voice-over-IP (VoIP), live streaming, or critical 5G applications requiring minimal delay.
• Example: Below scenario where specific links marked with a BLUE; affinity are exclusively utilized to manage high-throughput services. All ORANGE links are excluded.
FlexAlgo 129Configuration Sanapshot:
RTR1
!
hardware-profile filter twamp-ipv4 enable
!
qos enable
!
hostname RTR1
admin-group red 1
extended-admin-group green 32
extended-admin-group blue 93
!
delay-profile interfaces
mode two-way
burst-interval 1000
burst-count 1
interval 30
advertisement periodic threshold 70
advertisement periodic minimum-change 1000
advertisement accelerated
advertisement accelerated threshold 100
advertisement accelerated minimum-change 10000
!
router-id 25.0.1.1
!
segment-routing
global block 20000 80000
!
interface loopback1
ip address 25.0.0.1/32 secondary
ip router isis 1
!
interface loopback2
ip address 25.0.1.1/32 secondary
prefix-sid index 1
prefix-sid algorithm-num 128 index 1281
prefix-sid algorithm-num 129 index 1291
ip router isis 1
!
interface xe5
load-interval 30
ip address 11.0.12.1/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 10
isis te-maximum-delay flex-algo 20
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe15
speed 10g
load-interval 30
ip address 11.0.14.1/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 10
isis te-maximum-delay flex-algo 20
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe22
load-interval 30
ip address 11.0.15.1/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
delay-measurement dynamic twamp reflector-ip 11.0.15.5 reflector-port 862 sender-ip 11.0.15.1 sender-port 862
!
exit
!
twamp-light control
control-admin-state enable
!
router isis 1
is-type level-2-only
ignore-lsp-errors
capability flex-algo routing
flex-algo 129
metric-type link-delay
ti-lfa
exit-flex-algo
!
flex-algo 128
metric-type te-metric
ti-lfa
exit-flex-algo
!
lsp-gen-interval 1
max-lsp-lifetime 65535
spf-interval-exp 50 5000
metric-style wide
mpls traffic-eng router-id 25.0.1.1
mpls traffic-eng level-2
dynamic-hostname
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0000.0100.0000.1011.00
isis segment-routing global block 20000 80000
segment-routing mpls
!
router bgp 65010
bgp router-id 25.0.1.1
bgp auto-policy-soft-reset enable
no bgp inbound-route-filter
allocate-label all
neighbor 25.0.0.5 remote-as 65010
neighbor 25.0.0.5 update-source loopback1
neighbor 25.0.1.5 remote-as 65010
neighbor 25.0.1.5 update-source loopback2
!
address-family ipv4 unicast
neighbor 25.0.0.5 activate
exit-address-family
!
address-family vpnv4 unicast
neighbor 25.0.1.5 activate
exit-address-family
!
exit
!
!
end
RTR2
!
qos enable
!
hostname RTR2
admin-group red 1
admin-group orange 2
extended-admin-group green 32
extended-admin-group blue 93
port-group 2 speed 10g
!
router-id 25.0.1.2
!
segment-routing
global block 20000 80000
!
interface loopback1
ip address 25.0.0.2/32 secondary
ip router isis 1
!
interface loopback2
ip address 25.0.1.2/32 secondary
prefix-sid index 2
prefix-sid algorithm-num 128 index 1282
prefix-sid algorithm-num 129 index 1292
ip router isis 1
!
interface xe0
load-interval 30
ip address 11.0.25.2/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis admin-group flex-algo orange
isis extended-admin-group flex-algo green
!
interface xe1
load-interval 30
ip address 11.0.24.2/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis admin-group flex-algo red
isis admin-group flex-algo orange
!
interface xe14
load-interval 30
ip address 11.0.26.2/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis admin-group flex-algo red
isis extended-admin-group flex-algo blue
!
interface xe20
load-interval 30
ip address 11.0.12.2/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe21
load-interval 30
ip address 11.0.23.2/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
exit
!
router isis 1
is-type level-2-only
ignore-lsp-errors
capability flex-algo routing
flex-algo 128
metric-type te-metric
priority 131
ti-lfa
affinity-ag-exclude-any red
affinity-eag-include-any green
exit-flex-algo
!
flex-algo 129
metric-type link-delay
priority 131
ti-lfa
affinity-ag-exclude-any orange
affinity-eag-include-all blue
exclude-maximum-delay 25
exit-flex-algo
!
lsp-gen-interval 1
max-lsp-lifetime 65535
spf-interval-exp 50 5000
metric-style wide
mpls traffic-eng router-id 25.0.1.2
mpls traffic-eng level-2
dynamic-hostname
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0000.0100.0000.1022.00
isis segment-routing global block 20000 80000
segment-routing mpls
!
!
end
RTR3
!
hardware-profile filter twamp-ipv4 enable
!
qos enable
!
hostname RTR3
admin-group red 1
extended-admin-group green 32
extended-admin-group blue 93
!
router-id 25.0.1.3
!
segment-routing
global block 20000 80000
!
interface loopback1
ip address 25.0.0.3/32 secondary
ip router isis 1
!
interface loopback2
ip address 25.0.1.3/32 secondary
prefix-sid index 3
prefix-sid algorithm-num 128 index 1283
prefix-sid algorithm-num 129 index 1293
ip router isis 1
!
interface xe5
speed 10g
load-interval 30
ip address 11.0.35.3/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe21
speed 10g
load-interval 30
ip address 11.0.23.3/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe28
speed 10g
load-interval 30
ip address 11.0.36.3/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
exit
!
twamp-light reflector
reflector-admin-state enable
reflector-name R3-R5 reflector-ip ipv4 11.0.35.3 reflector-port 862 sender-ip ipv4 11.0.35.5 sender-port 862
!
router isis 1
is-type level-2-only
ignore-lsp-errors
capability flex-algo routing
flex-algo 129
metric-type link-delay
ti-lfa
exit-flex-algo
!
flex-algo 128
exit-flex-algo
!
lsp-gen-interval 1
max-lsp-lifetime 65535
spf-interval-exp 50 5000
metric-style wide
mpls traffic-eng router-id 25.0.1.3
mpls traffic-eng level-2
dynamic-hostname
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0000.0100.0000.1033.00
isis segment-routing global block 20000 80000
segment-routing mpls
!
router bgp 65010
bgp router-id 25.0.1.3
bgp auto-policy-soft-reset enable
no bgp inbound-route-filter
allocate-label all
neighbor 25.0.0.5 remote-as 65010
neighbor 25.0.0.5 update-source loopback1
neighbor 25.0.1.5 remote-as 65010
neighbor 25.0.1.5 update-source loopback2
!
address-family ipv4 unicast
neighbor 25.0.0.5 activate
exit-address-family
!
address-family vpnv4 unicast
neighbor 25.0.1.5 activate
exit-address-family
!
exit
!
!
end
RTR4
RTR4#show running-config
qos enable
!
hostname RTR4
!
admin-group red 1
extended-admin-group green 32
extended-admin-group blue 93
!
router-id 25.0.1.4
!
segment-routing
global block 20000 80000
!
interface loopback1
ip address 25.0.0.4/32 secondary
ip router isis 1
!
interface loopback2
ip address 25.0.1.4/32 secondary
prefix-sid index 4
prefix-sid algorithm-num 128 index 1284
prefix-sid algorithm-num 129 index 1294
ip router isis 1
!
interface xe1
speed 10g
load-interval 30
ip address 11.0.24.4/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 10
isis te-minimum-delay flex-algo 10
isis te-maximum-delay flex-algo 20
isis admin-group flex-algo red
isis admin-group flex-algo anomaly red
!
interface xe4
load-interval 30
ip address 11.0.45.4/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 10
isis te-minimum-delay flex-algo 10
isis te-maximum-delay flex-algo 20
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe15
load-interval 30
ip address 11.0.14.4/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 10
isis te-minimum-delay flex-algo 10
isis te-maximum-delay flex-algo 20
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
exit
!
router isis 1
is-type level-2-only
ignore-lsp-errors
capability flex-algo routing
flex-algo 128
metric-type te-metric
exit-flex-algo
!
flex-algo 129
metric-type link-delay
exit-flex-algo
!
lsp-gen-interval 1
max-lsp-lifetime 65535
spf-interval-exp 50 5000
metric-style wide
mpls traffic-eng router-id 25.0.1.4
mpls traffic-eng level-2
dynamic-hostname
set-overload-bit on-startup wait-for-bgp
bfd all-interfaces
net 49.0000.0100.0000.1044.00
isis segment-routing global block 20000 80000
segment-routing mpls
!
end
RTR5
!
hardware-profile filter twamp-ipv4 enable
!
qos enable
!
hostname RTR5
admin-group red 1
admin-group orange 2
extended-admin-group green 32
extended-admin-group blue 93
!
delay-profile interfaces
mode two-way
burst-interval 1000
burst-count 1
interval 30
advertisement periodic threshold 70
advertisement periodic minimum-change 1000
advertisement accelerated
advertisement accelerated threshold 100
advertisement accelerated minimum-change 10000
!
router-id 25.0.1.5
!
segment-routing
global block 20000 80000
!
interface loopback1
ip address 25.0.0.5/32 secondary
ip router isis 1
!
interface loopback2
ip address 25.0.1.5/32 secondary
prefix-sid index 5
prefix-sid algorithm-num 128 index 1285
prefix-sid algorithm-num 129 index 1295
ip router isis 1
!
interface xe1
load-interval 30
ip address 11.0.25.5/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis admin-group flex-algo orange
isis extended-admin-group flex-algo green
!
interface xe2
load-interval 30
ip address 11.0.45.5/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe5
load-interval 30
ip address 11.0.35.5/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
delay-measurement dynamic twamp reflector-ip 11.0.35.3 reflector-port 862 sender-ip 11.0.35.5 sender-port 862
!
interface xe17
speed 10g
load-interval 30
mtu 9216
label-switching
shutdown
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 10
isis te-maximum-delay flex-algo 20
isis admin-group flex-algo red
isis admin-group flex-algo anomaly red
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe19
load-interval 30
ip address 11.0.56.5/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe44
load-interval 30
ip address 11.0.15.5/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
exit
!
twamp-light reflector
reflector-admin-state enable
reflector-name R1-R5 reflector-ip ipv4 11.0.15.5 reflector-port 862 sender-ip ipv4 11.0.15.1 sender-port 862
!
twamp-light control
control-admin-state enable
!
router isis 1
is-type level-2-only
ignore-lsp-errors
capability flex-algo routing
flex-algo 128
metric-type te-metric
priority 130
ti-lfa
exit-flex-algo
!
flex-algo 129
metric-type link-delay
ti-lfa
exit-flex-algo
!
lsp-gen-interval 1
max-lsp-lifetime 65535
spf-interval-exp 50 5000
metric-style wide
mpls traffic-eng router-id 25.0.1.5
mpls traffic-eng level-2
dynamic-hostname
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0000.0100.0000.1055.00
redistribute isis level-2 into level-1
isis segment-routing global block 20000 80000
segment-routing mpls
!
router bgp 65010
bgp router-id 25.0.1.5
bgp auto-policy-soft-reset enable
no bgp inbound-route-filter
allocate-label all
neighbor 25.0.0.1 remote-as 65010
neighbor 25.0.0.1 update-source loopback1
neighbor 25.0.0.3 remote-as 65010
neighbor 25.0.0.3 update-source loopback1
neighbor 25.0.1.1 remote-as 65010
neighbor 25.0.1.1 update-source loopback2
neighbor 25.0.1.3 remote-as 65010
neighbor 25.0.1.3 update-source loopback2
!
address-family ipv4 unicast
neighbor 25.0.0.1 activate
neighbor 25.0.0.3 activate
exit-address-family
!
address-family vpnv4 unicast
neighbor 25.0.1.1 activate
neighbor 25.0.1.1 route-reflector-client
neighbor 25.0.1.3 activate
neighbor 25.0.1.3 route-reflector-client
exit-address-family
!
exit
!
!
end
RTR6
!
qos enable
!
hostname RTR6
admin-group red 1
extended-admin-group green 32
extended-admin-group blue 93
!
router-id 25.0.1.6
!
segment-routing
global block 20000 80000
!
interface loopback1
ip address 25.0.0.6/32 secondary
ip router isis 1
!
interface loopback2
ip address 25.0.1.6/32 secondary
prefix-sid index 6
prefix-sid algorithm-num 128 index 1286
prefix-sid algorithm-num 129 index 1296
ip router isis 1
!
interface xe12
load-interval 30
ip address 11.0.26.6/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis admin-group flex-algo red
isis extended-admin-group flex-algo blue
!
interface xe17
load-interval 30
ip address 11.0.56.6/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo green
isis extended-admin-group flex-algo blue
!
interface xe28
load-interval 30
ip address 11.0.36.6/24
mtu 9216
label-switching
isis network point-to-point
ip router isis 1
isis te-metric flex-algo ipv4 225
isis te-minimum-delay flex-algo 20
isis te-maximum-delay flex-algo 30
isis extended-admin-group flex-algo blue
isis extended-admin-group flex-algo green
!
exit
!
router isis 1
is-type level-2-only
ignore-lsp-errors
capability flex-algo routing
flex-algo 128
metric-type te-metric
ti-lfa
exit-flex-algo
!
flex-algo 129
metric-type link-delay
ti-lfa
exit-flex-algo
!
lsp-gen-interval 1
max-lsp-lifetime 65535
spf-interval-exp 50 5000
metric-style wide
mpls traffic-eng router-id 25.0.1.6
mpls traffic-eng level-2
dynamic-hostname
fast-reroute ti-lfa level-2 proto ipv4
bfd all-interfaces
net 49.0000.0100.0000.1066.00
isis segment-routing global block 20000 80000
segment-routing mpls
!
!
end
Validation
Verify the isis adjacencies are established and the routes are displaying correctly
RTR1#show clns neighbors
Total number of L1 adjacencies: 0
Total number of L2 adjacencies: 3
Total number of adjacencies: 3
Tag 1: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
RTR2 xe5 e8c5.7a2e.5631 Up 23 L2 IS-IS
RTR4 xe15 3412.7856.011c Up 19 L2 IS-IS
RTR5 xe22 80a2.353a.b78e Up 22 L2 IS-IS
RTR1#
RTR1#show ip isis route
Codes: C - connected, E - external, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, D - discard, e - external metric
** - invalid
Tag 1: VRF : default
Total number of routes: 23
Destination Metric Next-Hop Interface Tag
C 11.0.12.0/24 10 -- xe5 0
C 11.0.14.0/24 10 -- xe15 0
C 11.0.15.0/24 10 -- xe22 0
L2 11.0.23.0/24 20 11.0.12.2 xe5 0
L2 11.0.24.0/24 20 11.0.14.4 xe15 0
11.0.12.2 xe5 0
L2 11.0.25.0/24 20 11.0.12.2 xe5 0
11.0.15.5 xe22 0
L2 11.0.26.0/24 20 11.0.12.2 xe5 0
L2 11.0.35.0/24 20 11.0.15.5 xe22 0
L2 11.0.36.0/24 30 11.0.12.2 xe5 0
11.0.15.5 xe22 0
L2 11.0.45.0/24 20 11.0.14.4 xe15 0
11.0.15.5 xe22 0
L2 11.0.56.0/24 20 11.0.15.5 xe22 0
C 25.0.0.1/32 10 -- loopback1 0
L2 25.0.0.2/32 20 11.0.12.2 xe5 0
L2 25.0.0.3/32 30 11.0.12.2 xe5 0
11.0.15.5 xe22 0
L2 25.0.0.4/32 20 11.0.14.4 xe15 0
L2 25.0.0.5/32 20 11.0.15.5 xe22 0
L2 25.0.0.6/32 30 11.0.12.2 xe5 0
11.0.15.5 xe22 0
C 25.0.1.1/32 10 -- loopback2 0
L2 25.0.1.2/32 20 11.0.12.2 xe5 0
L2 25.0.1.3/32 30 11.0.12.2 xe5 0
11.0.15.5 xe22 0
L2 25.0.1.4/32 20 11.0.14.4 xe15 0
L2 25.0.1.5/32 20 11.0.15.5 xe22 0
L2 25.0.1.6/32 30 11.0.12.2 xe5 0
11.0.15.5 xe22 0
Verify the SR capability and its mapping table to check the mapping of the prefixes to algorithm and the prefix-sid
RTR1#show isis segment-routing capability
Tag 1 Segment-Routing:
-----------------------------------------------------
Advertisement Router Capability :25.0.1.1
Algorithm0 :0
Algorithm1 :129
Algorithm2 :128
SRMS Preference :0
Total SID'S Supported :60001
SR ERLD :10
SID Range List Count :1
SID's Range :20000 - 80000
Total SID's Supported (SRLB) :1920
SRLB Range List Count :1
SID's Range (SRLB) :14080 - 15999
-----------------------------------------------------
Advertisement Router Capability :25.0.1.2
Algorithm0 :0
Algorithm1 :128
Algorithm2 :129
SRMS Preference :0
Total SID'S Supported :60001
SR ERLD :6
SID Range List Count :1
SID's Range :20000 - 80000
Total SID's Supported (SRLB) :1920
SRLB Range List Count :1
SID's Range (SRLB) :14080 - 15999
-----------------------------------------------------
Advertisement Router Capability :25.0.1.3
Algorithm0 :0
Algorithm1 :129
Algorithm2 :128
SRMS Preference :0
Total SID'S Supported :60001
SR ERLD :10
SID Range List Count :1
SID's Range :20000 - 80000
Total SID's Supported (SRLB) :1920
SRLB Range List Count :1
SID's Range (SRLB) :14080 - 15999
-----------------------------------------------------
Advertisement Router Capability :25.0.1.4
Algorithm0 :0
Algorithm1 :128
Algorithm2 :129
SRMS Preference :0
Total SID'S Supported :60001
SR ERLD :6
SID Range List Count :1
SID's Range :20000 - 80000
Total SID's Supported (SRLB) :1920
SRLB Range List Count :1
SID's Range (SRLB) :14080 - 15999
-----------------------------------------------------
Advertisement Router Capability :25.0.1.5
Algorithm0 :0
Algorithm1 :128
Algorithm2 :129
SRMS Preference :0
Total SID'S Supported :60001
SR ERLD :6
SID Range List Count :1
SID's Range :20000 - 80000
Total SID's Supported (SRLB) :1920
SRLB Range List Count :1
SID's Range (SRLB) :14080 - 15999
-----------------------------------------------------
Advertisement Router Capability :25.0.1.6
Algorithm0 :0
Algorithm1 :128
Algorithm2 :129
SRMS Preference :0
Total SID'S Supported :60001
SR ERLD :6
SID Range List Count :1
SID's Range :20000 - 80000
Total SID's Supported (SRLB) :1920
SRLB Range List Count :1
SID's Range (SRLB) :14080 - 15999
RTR1#show isis segment-routing mapping-table ipv
ipv4 ipv6
RTR1#show isis segment-routing mapping-table ipv4 active
Tag 1 Segment-Routing:
Conflict Resolution Policy: Quarantine
Prefix Range Flags Algo/SID-Index/Prefix-Flag List
25.0.1.1/32 1 Algo:0 SID:1 PF:40
Algo:128 SID:1281 PF:40
Algo:129 SID:1291 PF:40
25.0.1.2/32 1 Algo:0 SID:2 PF:40
Algo:128 SID:1282 PF:40
Algo:129 SID:1292 PF:40
25.0.1.3/32 1 Algo:0 SID:3 PF:40
Algo:128 SID:1283 PF:40
Algo:129 SID:1293 PF:40
25.0.1.4/32 1 Algo:0 SID:4 PF:40
Algo:128 SID:1284 PF:40
Algo:129 SID:1294 PF:40
25.0.1.5/32 1 Algo:0 SID:5 PF:40
Algo:128 SID:1285 PF:40
Algo:129 SID:1295 PF:40
25.0.1.6/32 1 Algo:0 SID:6 PF:40
Algo:128 SID:1286 PF:40
Algo:129 SID:1296 PF:40
Number of mapping entries in Active IPv4 Table: 6
Verify the forwarding table for algo 0 and for the prefix 25.0.1.3/32 (destination)
RTR1#show mpls forwarding-table
Codes: > - installed FTN, * - selected FTN, p - stale FTN, ! - using backup
B - BGP FTN, K - CLI FTN, (t) - tunnel, P - SR Policy FTN, (b) - bypass,
L - LDP FTN, R - RSVP-TE FTN, S - SNMP FTN, I - IGP-Shortcut,
U - unknown FTN, O - SR-OSPF FTN, i - SR-ISIS FTN, k - SR-CLI FTN
(m) - FTN mapped over multipath transport, (e) - FTN is ECMP
FTN-ECMP LDP: Disabled, SR: Disabled
Code FEC FTN-ID Nhlfe-ID Tunnel-ID Pri Out-Label Out-Intf ELC Nexthop Algo-Num UpTime
i> 25.0.1.2/32 9 358 - - - - - - 128 00:20:40
6 0 Yes 3 xe5 No 11.0.12.2 - -
357 - No 21282 xe22 No 11.0.15.5 - -
i> 25.0.1.2/32 5 435 - - - - - - 129 00:12:05
6 0 Yes 3 xe5 No 11.0.12.2 - -
434 - No 21292 xe22 No 11.0.15.5 - -
i> 25.0.1.2/32 1 415 - - - - - - 0 00:20:40
6 0 Yes 3 xe5 No 11.0.12.2 - -
414 - No 20002 xe15 No 11.0.14.4 - -
i(b)> 25.0.1.2/32 17 352 2202 Yes 21282 xe5 No 11.0.12.2 128 00:12:03
i(b)> 25.0.1.2/32 19 355 2204 Yes 20002 xe5 No 11.0.12.2 0 00:12:03
i> 25.0.1.3/32 10 360 - - - - - - 128 00:20:40
111 0 Yes 21283 xe5 No 11.0.12.2 - -
31 - No 21283 xe22 No 11.0.15.5 - -
31 0 Yes 21283 xe22 No 11.0.15.5 - -
111 - No 21283 xe5 No 11.0.12.2 - -
i> 25.0.1.3/32 6 437 - - - - - - 129 00:12:05
421 0 Yes 21293 xe22 No 11.0.15.5 - -
6 - No 3 xe5 No 11.0.12.2 - -
i> 25.0.1.3/32 2 372 - - - - - - 0 00:20:40
102 0 Yes 20003 xe5 No 11.0.12.2 - -
22 - No 20003 xe22 No 11.0.15.5 - -
22 0 Yes 20003 xe22 No 11.0.15.5 - -
102 - No 20003 xe5 No 11.0.12.2 - -
i(b)> 25.0.1.3/32 27 164 2212 Yes 21293 xe5 No 11.0.12.2 129 00:09:50
i> 25.0.1.4/32 11 397 - - - - - - 128 00:20:40
1 0 Yes 3 xe15 No 11.0.14.4 - -
244 - No 21284 xe22 No 11.0.15.5 - -
i> 25.0.1.4/32 7 440 - - - - - - 129 00:12:05
1 0 Yes 3 xe15 No 11.0.14.4 - -
439 - No 21294 xe22 No 11.0.15.5 - -
i> 25.0.1.4/32 3 432 - - - - - - 0 00:20:40
1 0 Yes 3 xe15 No 11.0.14.4 - -
87 - No 20004 xe5 No 11.0.12.2 - -
i(b)> 25.0.1.4/32 24 393 2209 Yes 21284 xe15 No 11.0.14.4 128 00:11:46
i(b)> 25.0.1.4/32 25 395 2210 Yes 20004 xe15 No 11.0.14.4 0 00:11:46
i(b)> 25.0.1.4/32 28 109 2213 Yes 21294 xe15 No 11.0.14.4 129 00:09:50
i> 25.0.1.5/32 12 399 - - - - - - 128 00:20:40
13 0 Yes 3 xe22 No 11.0.15.5 - -
181 - No 21285 xe15 No 11.0.14.4 - -
i> 25.0.1.5/32 8 442 - - - - - - 129 00:12:05
13 0 Yes 3 xe22 No 11.0.15.5 - -
85 - No 21295 xe15 No 11.0.14.4 - -
i> 25.0.1.5/32 4 419 - - - - - - 0 00:20:40
13 0 Yes 3 xe22 No 11.0.15.5 - -
188 - No 20005 xe15 No 11.0.14.4 - -
i(b)> 25.0.1.5/32 16 350 2201 Yes 21285 xe22 No 11.0.15.5 128 00:12:03
i(b)> 25.0.1.5/32 18 37 2203 Yes 20005 xe22 No 11.0.15.5 0 00:12:03
i(b)> 25.0.1.5/32 26 428 2211 Yes 21295 xe22 No 11.0.15.5 129 00:09:50
i> 25.0.1.6/32 15 367 - - - - - - 128 00:20:40
34 0 Yes 21286 xe22 No 11.0.15.5 - -
171 - No 21286 xe5 No 11.0.12.2 - -
i> 25.0.1.6/32 14 444 - - - - - - 129 00:12:05
28 0 Yes 21296 xe22 No 11.0.15.5 - -
6 - No 3 xe5 No 11.0.12.2 - -
i> 25.0.1.6/32 13 378 - - - - - - 0 00:20:40
105 0 Yes 20006 xe5 No 11.0.12.2 - -
25 - No 20006 xe22 No 11.0.15.5 - -
25 0 Yes 20006 xe22 No 11.0.15.5 - -
105 - No 20006 xe5 No 11.0.12.2 - -
i(b)> 25.0.1.6/32 22 59 2207 Yes 21296 xe5 No 11.0.12.2 129 00:11:46
RTR1#show mpls forwarding-table 25.0.1.3/32
Codes: > - installed FTN, * - selected FTN, p - stale FTN, ! - using backup
B - BGP FTN, K - CLI FTN, (t) - tunnel, P - SR Policy FTN, (b) - bypass,
L - LDP FTN, R - RSVP-TE FTN, S - SNMP FTN, I - IGP-Shortcut,
U - unknown FTN, O - SR-OSPF FTN, i - SR-ISIS FTN, k - SR-CLI FTN
(m) - FTN mapped over multipath transport, (e) - FTN is ECMP
FTN-ECMP LDP: Disabled, SR: Disabled
Code FEC FTN-ID Nhlfe-ID Tunnel-ID Pri Out-Label Out-Intf ELC Nexthop Algo-Num UpTime
i> 25.0.1.3/32 10 360 - - - - - - 128 00:21:24
111 0 Yes 21283 xe5 No 11.0.12.2 - -
31 - No 21283 xe22 No 11.0.15.5 - -
31 0 Yes 21283 xe22 No 11.0.15.5 - -
111 - No 21283 xe5 No 11.0.12.2 - -
i> 25.0.1.3/32 6 437 - - - - - - 129 00:12:49
421 0 Yes 21293 xe22 No 11.0.15.5 - -
6 - No 3 xe5 No 11.0.12.2 - -
i> 25.0.1.3/32 2 372 - - - - - - 0 00:21:24
102 0 Yes 20003 xe5 No 11.0.12.2 - -
22 - No 20003 xe22 No 11.0.15.5 - -
22 0 Yes 20003 xe22 No 11.0.15.5 - -
102 - No 20003 xe5 No 11.0.12.2 - -
i(b)> 25.0.1.3/32 27 164 2212 Yes 21293 xe5 No 11.0.12.2 129 00:10:34
Verify the FAD of the winner node for flex-algo 128:
RTR1#show isis flex-algo 128 status winner detail
ISIS Instance : 1
Router-ID : 25.0.1.2, System-ID : 0100.0000.1022
Algorithm Number : 128
Metric Type : te-metric
Calculation Type : spf
Priority : 131 (Winner)
Prefix Metric Flag : No
Fwd-Exclude-Any-AG Mask :
(1)
Fwd-Include-Any-AG Mask : None
Fwd-Include-All-AG Mask : None
Rev-Exclude-Any-AG Mask : None
Rev-Include-Any-AG Mask : None
Rev-Include-All-AG Mask : None
Fwd-Exclude-Any-EAG Mask :
(1)
Fwd-Include-Any-EAG Mask :
(32)
Fwd-Include-All-EAG Mask : NULL
Rev-Exclude-Any-EAG Mask : NULL
Rev-Include-Any-EAG Mask : NULL
Rev-Include-All-EAG Mask : NULL
Exclude SRLG-ID List : NULL
Exclude Minimum Bandwidth : 0
Exclude Maximum Delay : 0
Intf-Group Mode Total B/W Calculate : No
Reference Bandwidth : 0
Granularity Bandwidth : 0
Verify the isis topology and forwarding-table for algorithm 128 are as per the configurations of FAD in the winner node:
RTR1#show isis topology algorithm 128
Tag 1: VRF : default
Flex-Algo : 128
IS-IS paths to level-2 routers
System Id Metric Next-Hop Interface SNPA
RTR1 --
RTR2 225 RTR2 xe5 e8c5.7a2e.5631
RTR3 450 RTR2 xe5 e8c5.7a2e.5631
RTR5 xe22 80a2.353a.b78e
RTR4 225 RTR4 xe15 3412.7856.011c
RTR5 225 RTR5 xe22 80a2.353a.b78e
RTR6 450 RTR5 xe22 80a2.353a.b78e
RTR1#show mpls forwarding-table algorithm
RTR1#show mpls forwarding-table algorithm 128
Codes: > - installed FTN, * - selected FTN, p - stale FTN, ! - using backup
B - BGP FTN, K - CLI FTN, (t) - tunnel, P - SR Policy FTN, (b) - bypass,
L - LDP FTN, R - RSVP-TE FTN, S - SNMP FTN, I - IGP-Shortcut,
U - unknown FTN, O - SR-OSPF FTN, i - SR-ISIS FTN, k - SR-CLI FTN
(m) - FTN mapped over multipath transport, (e) - FTN is ECMP
FTN-ECMP LDP: Disabled, SR: Disabled
Code FEC FTN-ID Nhlfe-ID Tunnel-ID Pri Out-Label Out-Intf ELC Nexthop Algo-Num UpTime
i> 25.0.1.2/32 9 358 - - - - - - 128 00:24:42
6 0 Yes 3 xe5 No 11.0.12.2 - -
357 - No 21282 xe22 No 11.0.15.5 - -
i(b)> 25.0.1.2/32 17 352 2202 Yes 21282 xe5 No 11.0.12.2 128 00:16:05
i> 25.0.1.3/32 10 360 - - - - - - 128 00:24:42
111 0 Yes 21283 xe5 No 11.0.12.2 - -
31 - No 21283 xe22 No 11.0.15.5 - -
31 0 Yes 21283 xe22 No 11.0.15.5 - -
111 - No 21283 xe5 No 11.0.12.2 - -
i> 25.0.1.4/32 11 397 - - - - - - 128 00:24:42
1 0 Yes 3 xe15 No 11.0.14.4 - -
244 - No 21284 xe22 No 11.0.15.5 - -
i(b)> 25.0.1.4/32 24 393 2209 Yes 21284 xe15 No 11.0.14.4 128 00:15:48
i> 25.0.1.5/32 12 399 - - - - - - 128 00:24:42
13 0 Yes 3 xe22 No 11.0.15.5 - -
181 - No 21285 xe15 No 11.0.14.4 - -
i(b)> 25.0.1.5/32 16 350 2201 Yes 21285 xe22 No 11.0.15.5 128 00:16:05
i> 25.0.1.6/32 15 367 - - - - - - 128 00:24:42
34 0 Yes 21286 xe22 No 11.0.15.5 - -
171 - No 21286 xe5 No 11.0.12.2 - -
RTR1#show mpls forwarding-table 25.0.1.3/32 algorithm 128
Codes: > - installed FTN, * - selected FTN, p - stale FTN, ! - using backup
B - BGP FTN, K - CLI FTN, (t) - tunnel, P - SR Policy FTN, (b) - bypass,
L - LDP FTN, R - RSVP-TE FTN, S - SNMP FTN, I - IGP-Shortcut,
U - unknown FTN, O - SR-OSPF FTN, i - SR-ISIS FTN, k - SR-CLI FTN
(m) - FTN mapped over multipath transport, (e) - FTN is ECMP
FTN-ECMP LDP: Disabled, SR: Disabled
Code FEC FTN-ID Nhlfe-ID Tunnel-ID Pri Out-Label Out-Intf ELC Nexthop Algo-Num UpTime
i> 25.0.1.3/32 10 360 - - - - - - 128 00:25:48
111 0 Yes 21283 xe5 No 11.0.12.2 - -
31 - No 21283 xe22 No 11.0.15.5 - -
31 0 Yes 21283 xe22 No 11.0.15.5 - -
111 - No 21283 xe5 No 11.0.12.2 - -
Verify the P, Q and PQ nodes are as the per the topology of flex-algo 128:
RTR1#show isis tilfa pq algorithm 128
Tag 1: Level-2 Link State Database:
Flex-Algo : 128
Node: RTR2.00-00
Interface xe5
P node: 0100.0000.1022 primary dist:450
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
P node: 0100.0000.1055 primary dist:225
P node: 0100.0000.1066 primary dist:450
Q node: 0100.0000.1022
Q node: 0100.0000.1033
Q node: 0100.0000.1055
Q node: 0100.0000.1066
Node Protecting P Nodes
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
P node: 0100.0000.1055 primary dist:225
P node: 0100.0000.1066 primary dist:450
PQ Node: RTR5.00-00 backup dist:10
No PQ Node found on backup path (Node Protection)
Node: RTR3.00-00
Interface xe5
P node: 0100.0000.1022 primary dist:450
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
P node: 0100.0000.1055 primary dist:225
P node: 0100.0000.1066 primary dist:450
Q node: 0100.0000.1022
Q node: 0100.0000.1033
Q node: 0100.0000.1055
Q node: 0100.0000.1066
Node Protecting P Nodes
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
P node: 0100.0000.1055 primary dist:225
P node: 0100.0000.1066 primary dist:450
PQ Node: RTR5.00-00 backup dist:10
PQ Node (Node Protection): RTR5.00-00 backup dist:10
Interface xe22
P node: 0100.0000.1022 primary dist:225
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
P node: 0100.0000.1055 primary dist:450
P node: 0100.0000.1066 primary dist:675
Q node: 0100.0000.1022
Q node: 0100.0000.1033
Q node: 0100.0000.1044
Q node: 0100.0000.1055
Q node: 0100.0000.1066
Node Protecting P Nodes
P node: 0100.0000.1022 primary dist:225
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
PQ Node: RTR2.00-00 backup dist:10
PQ Node (Node Protection): RTR2.00-00 backup dist:10
Node: RTR4.00-00
Interface xe15
P node: 0100.0000.1022 primary dist:225
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:450
P node: 0100.0000.1055 primary dist:225
P node: 0100.0000.1066 primary dist:450
Q node: 0100.0000.1033
Q node: 0100.0000.1044
Q node: 0100.0000.1055
Q node: 0100.0000.1066
Node Protecting P Nodes
P node: 0100.0000.1022 primary dist:225
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1055 primary dist:225
P node: 0100.0000.1066 primary dist:450
PQ Node: RTR5.00-00 backup dist:10
No PQ Node found on backup path (Node Protection)
Node: RTR5.00-00
Interface xe22
P node: 0100.0000.1022 primary dist:225
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
P node: 0100.0000.1055 primary dist:450
P node: 0100.0000.1066 primary dist:675
Q node: 0100.0000.1022
Q node: 0100.0000.1033
Q node: 0100.0000.1044
Q node: 0100.0000.1055
Q node: 0100.0000.1066
Node Protecting P Nodes
P node: 0100.0000.1022 primary dist:225
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
PQ Node: RTR4.00-00 backup dist:10
No PQ Node found on backup path (Node Protection)
Node: RTR6.00-00
Interface xe22
P node: 0100.0000.1022 primary dist:225
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
P node: 0100.0000.1055 primary dist:450
P node: 0100.0000.1066 primary dist:675
Q node: 0100.0000.1022
Q node: 0100.0000.1033
Q node: 0100.0000.1044
Q node: 0100.0000.1055
Q node: 0100.0000.1066
Node Protecting P Nodes
P node: 0100.0000.1022 primary dist:225
P node: 0100.0000.1033 primary dist:450
P node: 0100.0000.1044 primary dist:225
PQ Node: RTR4.00-00 backup dist:10
PQ Node (Node Protection): RTR2.00-00 backup dist:10
RTR1#
RTR1#
RTR1#show ip isis route tilfa algorithm 128
Tag : 1 VRF : default
Flex-Algo : 128
Codes : L1 - IS-IS level-1, L2 - IS-IS level-2,
C - Connected Routes, ia - IS-IS inter area
25.0.1.2/32
Route type: L2, FTN-ix :9 ILM-ix :15
SR Incoming Label : 21282
Primary Path Nexthop : 11.0.12.2, xe5
SR outgoing Label : 3
PQ node : 25.0.1.5
Backup outgoing Label: 21282
Bypass_trunk id : 2201
Backup out interface : xe22
Protection Type : Link Protecting
Trunk : 2202 :25.0.1.2_nh_10026_ALG128 FTN-ix : 17 ref_cnt:2
Number Of outgoing label : 1
21282
Nexthop address : 11.0.12.2
25.0.1.3/32
Route type: L2, FTN-ix :10 ILM-ix :16
SR Incoming Label : 21283
Primary Path Nexthop : 11.0.12.2, xe5
SR outgoing Label : 21283
PQ node : 25.0.1.5
Backup outgoing Label: 21283
Bypass_trunk id : 2201
Backup out interface : xe22
Protection Type : Node Protecting
Primary Path Nexthop : 11.0.15.5, xe22
SR outgoing Label : 21283
PQ node : 25.0.1.2
Backup outgoing Label: 21283
Bypass_trunk id : 2202
Backup out interface : xe5
Protection Type : Node Protecting
25.0.1.4/32
Route type: L2, FTN-ix :11 ILM-ix :17
SR Incoming Label : 21284
Primary Path Nexthop : 11.0.14.4, xe15
SR outgoing Label : 3
PQ node : 25.0.1.5
Backup outgoing Label: 21284
Bypass_trunk id : 2201
Backup out interface : xe22
Protection Type : Link Protecting
Trunk : 2209 :25.0.1.4_nh_10036_ALG128 FTN-ix : 24 ref_cnt:1
Number Of outgoing label : 1
21284
Nexthop address : 11.0.14.4
25.0.1.5/32
Route type: L2, FTN-ix :12 ILM-ix :18
SR Incoming Label : 21285
Primary Path Nexthop : 11.0.15.5, xe22
SR outgoing Label : 3
PQ node : 25.0.1.4
Backup outgoing Label: 21285
Bypass_trunk id : 2209
Backup out interface : xe15
Protection Type : Link Protecting
Trunk : 2201 :25.0.1.5_nh_10043_ALG128 FTN-ix : 16 ref_cnt:3
Number Of outgoing label : 1
21285
Nexthop address : 11.0.15.5
25.0.1.6/32
Route type: L2, FTN-ix :15 ILM-ix :21
SR Incoming Label : 21286
Primary Path Nexthop : 11.0.15.5, xe22
SR outgoing Label : 21286
PQ node : 25.0.1.2
Backup outgoing Label: 21286
Bypass_trunk id : 2202
Backup out interface : xe5
Protection Type : Node Protecting