MPLS LDP-IGP Synchronization
This chapter contains configurations for MPLS LDP-IGP Synchronization.
Overview
Multi-Protocol Label Switching (MPLS) Label Distribution Protocol (LDP) Interior Gateway Protocol (IGP) Synchronization ensures that LDP is fully established before the IGP path is used for switching. In certain networks, there is dependency on the edge-to-edge Label Switched Paths (LSPs) setup by the Label Distribution Protocol (LDP), e.g., networks that are used for Multi-Protocol Label Switching (MPLS) Virtual Private Network (VPN) applications. For such applications, it is not possible to rely on Internet Protocol (IP) forwarding if the MPLS LSP is not operating appropriately. Labelled traffic can be dropped due to presence of black holes in situations where the Interior Gateway Protocol (IGP) is operational on a link but LDP sessions are not up as the label distribution is not completed. While the link could still be used for IP forwarding, it is not useful for MPLS forwarding, for example, MPLS VPN applications or Border Gateway Protocol (BGP) route-free cores.
The MPLS LDP-IGP Synchronization feature ensures that the Label Distribution Protocol (LDP) is fully established before the Interior Gateway Protocol (IGP) path is used for packet forwarding. It is useful for cases in which the router is the ingress and the decision of whether to take the MPLS LSP or IGP path is decided there.
LDP-IGP synchronization is an interface level feature. It can be selectively enabled in the required interfaces. For each interface there are two commands available for synchronization, one each for IS-IS. Once configured the IGP saves the required information, and also notifies LDP. In between the IGP increases the link cost to maximum and sends advertisements to its peer. This discourages its peers from taking routes that pass via it.
When all LDP sessions hosted on the interface become operational, it sends a notification to the IGP. This is termed as LDP convergence. The IGP then advertises normal cost, so that all traffic now coming to the interface takes the MPLS LSP path established by LDP and not be IP routed.
Prerequisites
Only interfaces that are running Open Shortest Path First (OSPF) or Intermediate System-to-Intermediate System (IS-IS) processes are capable of LDP-IGP synchronization. The router must also be running LDP.
Topology
The sample topology diagram is applicable to all configurations in this chapter.
Sample Topology for LDP-IGP Synchronization
LDP-IGP Synchronization with OSPF
When IGP synchronization is enabled on OSPF-enabled interfaces, OSPF sends Maximum/Normal cost based on LDP session Down or Up state messages to interfaces until the hold-down-timer expires or synchronization is achieved.
Before configuring LDP-IGP synchronization, the NSM, OSPF and LDP configurations must be completed. The tables below contain examples of how this is done.
RTR1-NSM
#configure terminal | Enter configuration mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#ip address 10.10.10.1/24 | Configure IPv4 address for xe11. |
(config-if)#label-switching | Enable label switching on interface xe11. |
(config-if)#exit | Exit interface mode. |
(config)#interface lo | Specify the loopback (lo) interface to be configured. |
(config-if)#ip address 1.1.1.1/32 secondary | Set the IP address of the loopback interface to 1.1.1.1/32. |
RTR1-OSPF
(config)#router ospf 100 | Configure the routing process and specify the Process ID 100. The Process ID should be a unique positive integer identifying the routing process. |
(config-router)# router-id 1.1.1.1 | Configure router id for OSPF |
(config-router)#network 10.10.10.0/24 area 0 (config-router)#network 1.1.1.1/32 area 0 | Define the interface on which OSPF runs and associate the area ID (0) with the interface. |
RTR1-LDP
(config)#router ldp | Enter router mode for LDP. |
(config-router)#router-id 1.1.1.1 | Set the router ID to IP address 1.1.1.1. |
(config-router)#transport-address ipv4 1.1.1.1 | Configure the transport address for IPV4 (for IPV6 use ipv6) to be used for a TCP session over which LDP will run. Note: It is preferable to use the loopback address as the transport address. |
(config-router)#exit | Exit router mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#enable-ldp ipv4 | Enable LDP for IPv4 on xe11. |
(config-if)#exit | Exit interface mode. |
RTR2-NSM
#configure terminal | Enter configuration mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#ip address 10.10.10.2/24 | Configure IPv4 address for xe11. |
(config-if)#label-switching | Enable label switching on interface xe11. |
(config-if)#exit | Exit interface mode. |
(config)#interface lo | Specify the loopback (lo) interface to be configured. |
(config-if)#ip address 2.2.2.2/32 secondary | Set the IP address of the loopback interface to 2.2.2.2/32. |
RTR2-OSPF
(config)#router ospf 100 | Configure the routing process and specify the Process ID 100. The Process ID should be a unique positive integer identifying the routing process. |
(config-router)# router-id 2.2.2.2 | Configure router id for OSPF |
(config-router)#network 10.10.10.0/24 area 0 (config-router)#network 2.2.2.2/32 area 0 | Define the interface on which OSPF runs and associate the area ID (0) with the interface. |
RTR2-LDP
(config)#router ldp | Enter Router mode for LDP. |
(config-router)#router-id 2.2.2.2 | Set the router ID to IP address 2.2.2.2. |
(config-router)#transport-address ipv4 2.2.2.2 | Configure the transport address for IPV4 (for IPV6 use ipv6) to be used for a TCP session over which LDP will run. Note: It is preferable to use the loopback address as transport address. |
(config-router)#exit | Exit the Router mode and return to the Configure mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#enable-ldp ipv4 | Enable LDP for IPv4 on xe11. |
(config-if)#exit | Exit interface mode. |
Validation
R1#show ip ospf neighbor
Total number of full neighbors: 1
OSPF process 100 VRF(default):
Neighbor ID Pri State Dead Time Address Interface Instance ID
2.2.2.2 1 Full/DR 00:00:33 10.10.10.2 xe11 0
R2#show ip ospf neighbor
Total number of full neighbors: 1
OSPF process 100 VRF(default):
Neighbor ID Pri State Dead Time Address Interface Instance ID
1.1.1.1 1 Full/Backup 00:00:31 10.10.10.1 xe11 0
R2#
R1#show ldp session
Peer IP Address IF Name My Role State KeepAlive UpTime
2.2.2.2 xe11 Passive OPERATIONAL 30 00:06:03
R2#show ldp session
Peer IP Address IF Name My Role State KeepAlive UpTime
1.1.1.1 xe11 Active OPERATIONAL 30 00:06:31
R1#show ldp adjacency
IP Address Mode Intf Name Holdtime LDP-Identifier
10.10.10.2 Interface xe11 15 2.2.2.2:0
R2#show ldp adjacency
IP Address Mode Intf Name Holdtime LDP-Identifier
10.10.10.1 Interface xe11 15 1.1.1.1:0
R1#show ip ospf interface
lo is up, line protocol is up
Internet Address 1.1.1.1/32, Area 0.0.0.0, MTU 16436
Process ID 100, VRF (default), Router ID 1.1.1.1, Network Type LOOPBACK, Cost: 1
Transmit Delay is 1 sec, State Loopback, TE Metric 1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
xe11 is up, line protocol is up
Internet Address 10.10.10.1/24, Area 0.0.0.0, MTU 1500
Process ID 100, VRF (default), Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State Backup, Priority 1, TE Metric 1
Designated Router (ID) 2.2.2.2, Interface Address 10.10.10.2
Backup Designated Router (ID) 1.1.1.1, Interface Address 10.10.10.1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:01
Neighbor Count is 1, Adjacent neighbor count is 1
Hello received 61 sent 62, DD received 3 sent 6
LS-Req received 1 sent 1, LS-Upd received 4 sent 5
LS-Ack received 4 sent 3, Discarded 0
No authentication
R2#sh ip ospf interface
lo is up, line protocol is up
Internet Address 2.2.2.2/32, Area 0.0.0.0, MTU 16436
Process ID 100, VRF (default), Router ID 2.2.2.2, Network Type LOOPBACK, Cost: 1
Transmit Delay is 1 sec, State Loopback, TE Metric 1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
xe11 is up, line protocol is up
Internet Address 10.10.10.2/24, Area 0.0.0.0, MTU 1500
Process ID 100, VRF (default), Router ID 2.2.2.2, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1, TE Metric 1
Designated Router (ID) 2.2.2.2, Interface Address 10.10.10.2
Backup Designated Router (ID) 1.1.1.1, Interface Address 10.10.10.1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:01
Neighbor Count is 1, Adjacent neighbor count is 1
Hello received 62 sent 63, DD received 6 sent 3
LS-Req received 1 sent 1, LS-Upd received 5 sent 4
LS-Ack received 3 sent 4, Discarded 0
No authentication
R1#show mpls ldp igp sync
R1#
R2#show mpls ldp igp sync
R2#
LDP-IGP Synchronization
Now that NSM, OSPF and LDP are all enabled, the LDP-IGP synchronization can be configured.
RTR1
(config)#interface xe11 | Enter interface mode. |
(config-if)#mpls ldp-igp sync ospf holddown-timer 500 | Enable LDP-IGP Synchronization for xe11 belonging to an OSPF process and 500 seconds is holddown-timer value for IGP to wait until LDP converges. OSPF: This command is part of OSPF Process. Note: Holddown-timer range is 1 to 2147483 seconds. If holddown timer is not configured, IGP waits indefinitely for LDP to converge. Use the command mpls ldp-igp sync ospf to configure without a holddown-timer. |
(config-if)#mpls ldp-igp sync-delay 60 | Configure time delay in seconds for notification of LDP convergence to IGP. This is not applicable for notification of non-convergence. Range is 5 to 60 seconds. This command is optional. LDP: This command is part of LDP Process. Default: If not configured the delay is 0 seconds. |
(config-if)#exit | Exit interface mode. |
RTR2
(config)#interface xe11 | Enter interface mode. |
(config-if)#mpls ldp-igp sync ospf holddown-timer 500 | Enable LDP-IGP Synchronization for interfaces (xe11) belonging to an OSPF process.and 500 secs is Holddown-timer value for IGP to wait until LDP Converge. OSPF: This command is part of the OSPF Process.vNote: Holddown-timer range is <1-2147483> seconds. If holddown timer is not configured, IGP waits indefinitely for LDP to converge. Use command mpls ldp-igp sync ospf to configure without a holddown-timer. |
(config-if)#mpls ldp-igp sync-delay 60 | Configure the time delay in seconds for the notification of LDP convergence to IGP. (This is not applicable for notification of non-convergence.) Range is 5 to 60 seconds. This command is optional. LDP: This command is part of LDP Process. Default: If not configured the delay is 0 seconds. |
(config-if)#exit | Exit interface mode. |
RTR1 Validation
When LDP IGP SYNC is Configured with hold-down and sync-delay timer
R1#show ip ospf interface
lo is up, line protocol is up
Internet Address 1.1.1.1/32, Area 0.0.0.0, MTU 16436
Process ID 100, VRF (default), Router ID 1.1.1.1, Network Type LOOPBACK, Cost:
1
Transmit Delay is 1 sec, State Loopback, TE Metric 1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
xe11 is up, line protocol is up
Internet Address 10.10.10.1/24, Area 0.0.0.0, MTU 1500
Process ID 100, VRF (default), Router ID 1.1.1.1, Network Type BROADCAST, Cost
: 1
Transmit Delay is 1 sec, State Backup, Priority 1, TE Metric 1
LDP-OSPF Sync configured
Holddown timer : 500 seconds, Remaining time = 0 seconds
Designated Router (ID) 2.2.2.2, Interface Address 10.10.10.2
Backup Designated Router (ID) 1.1.1.1, Interface Address 10.10.10.1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:06
Neighbor Count is 1, Adjacent neighbor count is 1
Hello received 178 sent 179, DD received 3 sent 6
LS-Req received 1 sent 1, LS-Upd received 5 sent 6
LS-Ack received 5 sent 4, Discarded 0
No authentication
R1#
R1#show mpls ldp igp sync
xe11 is up, line protocol is up
LDP configured; LDP-IGP Synchronization enabled.
Session IP Address : 2.2.2.2
Sync status: Achieved
Delay timer: Configured, 60 seconds, Not Running
RTR2 Validation
R2#show ip ospf interface
lo is up, line protocol is up
Internet Address 2.2.2.2/32, Area 0.0.0.0, MTU 16436
Process ID 100, VRF (default), Router ID 2.2.2.2, Network Type LOOPBACK, Cost:
1
Transmit Delay is 1 sec, State Loopback, TE Metric 1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
xe11 is up, line protocol is up
Internet Address 10.10.10.2/24, Area 0.0.0.0, MTU 1500
Process ID 100, VRF (default), Router ID 2.2.2.2, Network Type BROADCAST, Cost
: 1
Transmit Delay is 1 sec, State DR, Priority 1, TE Metric 1
LDP-OSPF Sync configured
Holddown timer : 500 seconds, Remaining time = 0 seconds
Designated Router (ID) 2.2.2.2, Interface Address 10.10.10.2
Backup Designated Router (ID) 1.1.1.1, Interface Address 10.10.10.1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:01
Neighbor Count is 1, Adjacent neighbor count is 1
Hello received 211 sent 211, DD received 6 sent 3
LS-Req received 1 sent 1, LS-Upd received 8 sent 7
LS-Ack received 6 sent 7, Discarded 0
No authentication
R2#
R2#show mpls ldp igp sync
xe11 is up, line protocol is up
LDP configured; LDP-IGP Synchronization enabled.
Session IP Address : 1.1.1.1
Sync status: Achieved
Delay timer: Configured, 60 seconds, Not Running
LDP-IGP Synchronization with IS-IS
When IGP synchronization is enabled on an IS-IS enabled interfaces, IS-IS sends Maximum/Normal cost based on LDP session or Up state on interfaces until hold-down-timer expires or synchronization is achieved.
Before configuring LDP-IGP synchronization, the NSM, IS-IS and LDP configurations must be completed. The tables below contain examples of how this is done.
RTR1-NSM
#configure terminal | Enter configuration mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#ip address 10.10.10.1/24 | Set the IP address of the xe11 to 10.10.10.1/24. |
(config-if)#label-switching | Enable label switching on xe11. |
(config-if)#exit | Exit interface mode. |
(config)#interface lo | Specify the loopback (lo) interface to be configured. |
(config-if)#ip address 1.1.1.1/32 secondary | Set the IP address of the loopback interface to 1.1.1.1/32. |
(config-if)#exit | Exit interface mode. |
RTR1-IS-IS
(config)#router isis 1 | Configure the IS-IS routing instance and specify the TAG (1). The TAG should be a WORD - ISO routing area tag. |
(config-router)#is-type level-1 | Define the IS to the specified level of routing for router. |
(config-router)#net 49.0001.0000.0000.0001.00 | Configure the Network Entity Title (NET) for the instance. |
(config-router)#exit | Exit the Router mode and return to the Configure mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#ip router isis 1 | Configure IS-IS IPv4 routing on the interface with IS-IS tag instance 1. |
(config-if)#isis circuit-type level-1 | Define the circuit type for the interface on which IS-IS runs and associate the level 1. |
(config-if)#exit | Exit interface mode. |
(config)#interface lo | Enter interface mode for the loopback interface (lo). |
(config-if)#ip router isis 1 | Configure IS-IS IPv4 routing on the interface with IS-IS tag instance 1. |
(config-if)#isis circuit-type level-1 | Define the circuit type for the interface on which IS-IS runs and associate the level 1. |
(config-if)#exit | Exit interface mode. |
RTR1-LDP
(config)#router ldp | Enter Router mode for LDP. |
(config-router)#router-id 1.1.1.1 | Set the router ID to IP address 1.1.1.1. |
(config-router)#transport-address ipv4 1.1.1.1 | Configure the transport address for IPV4 (for IPv6 use an IPv6 address) to use for a TCP session over which LDP will run. Note: It is preferable to use the loopback address as transport address. |
(config-router)#exit | Exit the Router mode and return to the Configure mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#enable-ldp ipv4 | Enable LDP for IPv4 on xe11. |
(config-if)#exit | Exit interface mode. |
RTR2-NSM
#configure terminal | Enter configuration mode |
(config)#interface xe11 | Enter interface mode. |
(config-if)#ip address 10.10.10.2/24 | Set the IP address of xe11 to 10.10.10.2/24 |
(config-if)#label-switching | Enable label switching on interface xe11. |
(config-if)#exit | Exit interface mode. |
(config)#interface lo | Specify the loopback (lo) interface to be configured. |
(config-if)#ip address 2.2.2.2/32 secondary | Set the IP address of the loopback interface to 2.2.2.2/32. |
(config-if)#exit | Exit interface mode. |
RTR2-IS-IS
(config)#router isis 1 | Configure the IS-IS routing instance and specify the TAG as 1. The TAG should be a WORD - ISO routing area tag. |
(config-router)#is-type level-1 | Define the IS to the specified level of routing for router. |
(config-router)#net 49.0001.0000.0000.0002.00 | Configure the Network Entity Title (NET) for the instance. |
(config-router)#exit | Exit the Router mode and return to the Configure mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#ip router isis 1 | Configure IS-IS IPv4 routing on the interface with is-is tag instance 1. |
(config-if)#isis circuit-type level-1 | Define the circuit type for the interface on which IS-IS runs and associate the level type (1). |
(config-if)#exit | Exit interface mode. |
(config)#interface lo | Enter interface mode for the loopback (lo) interface. |
(config-if)#ip router isis 1 | Configure IS-IS IPv4 routing on the interface with IS-IS tag instance 1. |
(config-if)#isis circuit-type level-1 | Define the circuit type for the interface on which IS-IS runs and associate the level 1. |
(config-if)#exit | Exit interface mode. |
RTR2-LDP
(config)#router ldp | Enter Router mode for LDP. |
(config-router)#router-id 2.2.2.2 | Set the router ID to IP address 2.2.2.2. |
(config-router)#transport-address ipv4 2.2.2.2 | Configure the transport address for IPv4 (for IPv6 use an IPv6 address) to use for a TCP session over which LDP will run. Note: It is preferable to use the loopback address as transport address. |
(config-router)#exit | Exit the Router mode and return to the Configure mode. |
(config)#interface xe11 | Enter interface mode. |
(config-if)#enable-ldp ipv4 | Enable LDP for IPv4 on xe11. |
(config-if)#exit | Exit interface mode. |
Validation
R1#show clns neighbors
Total number of L1 adjacencies: 1
Total number of L2 adjacencies: 0
Total number of adjacencies: 1
Tag 1: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
0000.0000.0002 xe11 6cb9.c5cf.da69 Up 24 L1 IS-IS
R2#show clns neighbors
Total number of L1 adjacencies: 1
Total number of L2 adjacencies: 0
Total number of adjacencies: 1
Tag 1: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
0000.0000.0001 xe11 b86a.97d1.24d1 Up 9 L1 IS-IS
R1#show clns is-neighbors
Tag 1: VRF : default
System Id Interface State Type Priority Circuit Id
0000.0000.0002 xe11 Up L1 64 0000.0000.0001.01
R2#show clns is-neighbors
Tag 1: VRF : default
System Id Interface State Type Priority Circuit Id
0000.0000.0001 xe11 Up L1 64 0000.0000.0001.01
R1#show ldp session
Peer IP Address IF Name My Role State KeepAlive UpTime
2.2.2.2 xe11 Passive OPERATIONAL 30 00:08:08
R1#show ldp adjacency
IP Address Mode Intf Name Holdtime LDP-Identifier
10.10.10.2 Interface xe11 15 2.2.2.2:0
R2#show ldp session
Peer IP Address IF Name My Role State KeepAlive UpTime
1.1.1.1 xe11 Active OPERATIONAL 30 00:08:24
R2#show ldp adjacency
IP Address Mode Intf Name Holdtime LDP-Identifier
10.10.10.1 Interface xe11 15 1.1.1.1:0
R1#show isis interface xe11
xe11 is up, line protocol is up
Routing Protocol: IS-IS (1)
Network Type: Broadcast
Circuit Type: level-1
Local circuit ID: 0x01
Extended Local circuit ID: 0x0000271C
Local SNPA: b86a.97d1.24d1
IP interface address:
10.10.10.1/24
IPv6 interface address:
fe80::ba6a:97ff:fed1:24d1/64
Level-1 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0001.01
Number of active level-1 adjacencies: 1
Level-1 LSP MTU: 1492
Next IS-IS LAN Level-1 Hello in 792 milliseconds
R2#show isis interface xe11
xe11 is up, line protocol is up
Routing Protocol: IS-IS (1)
Network Type: Broadcast
Circuit Type: level-1
Local circuit ID: 0x01
Extended Local circuit ID: 0x0000271B
Local SNPA: 6cb9.c5cf.da69
IP interface address:
10.10.10.2/24
IPv6 interface address:
fe80::6eb9:c5ff:fecf:da69/64
Level-1 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0001.01
Number of active level-1 adjacencies: 1
Level-1 LSP MTU: 1492
Next IS-IS LAN Level-1 Hello in 1 seconds
R1#show isis database detail
Tag 1: VRF : default
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0000.0001.00-00* 0x00000002 0xB193 516 0/0/0
Area Address: 49.0001
NLPID: 0xCC
IP Address: 10.10.10.1
Metric: 10 IS 0000.0000.0001.01
Metric: 10 IP 10.10.10.0 255.255.255.0
Metric: 10 IP 1.1.1.1 255.255.255.255
0000.0000.0001.01-00* 0x00000001 0x1FBD 516 0/0/0
Metric: 0 IS 0000.0000.0001.00
Metric: 0 IS 0000.0000.0002.00
0000.0000.0002.00-00 0x00000002 0x84BA 519 0/0/0
Area Address: 49.0001
NLPID: 0xCC
IP Address: 10.10.10.2
Metric: 10 IS 0000.0000.0001.01
Metric: 10 IP 10.10.10.0 255.255.255.0
Metric: 10 IP 2.2.2.2 255.255.255.255
R2#show isis database detail
Tag 1: VRF : default
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0000.0001.00-00 0x00000002 0xB193 521 0/0/0
Area Address: 49.0001
NLPID: 0xCC
IP Address: 10.10.10.1
Metric: 10 IS 0000.0000.0001.01
Metric: 10 IP 10.10.10.0 255.255.255.0
Metric: 10 IP 1.1.1.1 255.255.255.255
0000.0000.0001.01-00 0x00000001 0x1FBD 521 0/0/0
Metric: 0 IS 0000.0000.0001.00
Metric: 0 IS 0000.0000.0002.00
0000.0000.0002.00-00* 0x00000002 0x84BA 526 0/0/0
Area Address: 49.0001
NLPID: 0xCC
IP Address: 10.10.10.2
Metric: 10 IS 0000.0000.0001.01
Metric: 10 IP 10.10.10.0 255.255.255.0
Metric: 10 IP 2.2.2.2 255.255.255.255
R1#show mpls ldp igp sync
R1#
R2#show mpls ldp igp sync
R2#
LDP-IGP SYNC Configuration
Now that NSM, IS-IS and LDP are all enabled, the LDP-IGP synchronization can be configured.
RTR1
(config)#interface xe11 | Enter interface mode. |
(config-if)#mpls ldp-igp sync isis level-1 holddown-timer 700 | Configure LDP-IGP Synchronization for interface xe11 belonging to an IS-IS process with corresponding IS-IS level.700 seconds is the holddown-timer value for IGP to wait until LDP converges. The values level-1|level-2-only|level-1-2 identify the IS-IS level instance. The interface can be acting on any level, but the sync is applicable only when it matches with the level given in IGP sync command. IS-IS: This command is part of ISIS Process. Default: Mandatory configuration. No default option. Note: The holddown-timer Range is 1 to 2147483 seconds. If no holddown timer is configured, IGP waits indefinitely for LDP to Converge. Use the command mpls ldp-igp sync is-is <level-type> to configure without a holddown-timer. |
(config-if)#mpls ldp-igp sync-delay 55 | Set the time delay in seconds for the notification of LDP convergence to IGP. This is not applicable for notification of non-convergence. Range is 5 to 60 seconds. This command is optional. LDP: This command is part of LDP Process. Default: If not configured, the delay is 0 seconds. |
(config-if)#exit | Exit interface mode. |
LDP-IGP SYNC Configuration
Now that NSM, IS-IS and LDP are all enabled, the LDP-IGP synchronization can be configured.
RTR2
(config)#interface xe11 | Enter interface mode. |
(config-if)#mpls ldp-igp sync isis level-1 holddown-timer 700 | Configure LDP-IGP Synchronization for interface xe11 belonging to an IS-IS process with corresponding IS-IS level.700 secs is the holddown-timer value for IGP to wait until LDP converges. The parameters level-1|level-2-only|level-1-2 identify the IS-IS instance level. The interface can be acting on any level, but sync is applicable only when it matches with the level given in IGP sync command. IS-IS: This command is part of IS-IS Process. Default: Mandatory configuration. No default option. Note: The holddown-timer Range is 1 to 2147483 seconds. If no holddown timer is configured, IGP waits indefinitely for LDP to Converge. Use command mpls ldp-igp sync is-is <level-type> to configure without a holddown-timer. |
(config-if)#mpls ldp-igp sync-delay 55 | Set the time delay in seconds for notification of LDP convergence to IGP. This is not applicable for notification of non-convergence. Range is 5 to 60 seconds. This command is optional. LDP: This command is part of LDP Process. Default: If not configured, the delay is 0 seconds. |
(config-if)#exit | Exit interface mode. |
RTR1 Validation
When LDP IGP SYNC is Configured with hold-down and sync-delay timer
R1#show isis interface xe11
xe11 is up, line protocol is up
Routing Protocol: IS-IS (1)
Network Type: Broadcast
Circuit Type: level-1
Local circuit ID: 0x01
Extended Local circuit ID: 0x0000271C
Local SNPA: b86a.97d1.24d1
IP interface address:
10.10.10.1/24
IPv6 interface address:
fe80::ba6a:97ff:fed1:24d1/64
LDP-ISIS Sync Configured
Holddown timer = 700 seconds, Remaining time = 0 seconds
Level-1 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0001.01
Number of active level-1 adjacencies: 1
Level-1 LSP MTU: 1492
Next IS-IS LAN Level-1 Hello in 420 milliseconds
R1#
R1#show mpls ldp igp sync
xe11 is up, line protocol is up
LDP configured; LDP-IGP Synchronization enabled.
Session IP Address : 2.2.2.2
Sync status: Achieved
Delay timer: Configured, 55 seconds, Not Running
R1#
RTR2 Validation
R2#show isis interface xe11
xe11 is up, line protocol is up
Routing Protocol: IS-IS (1)
Network Type: Broadcast
Circuit Type: level-1
Local circuit ID: 0x01
Extended Local circuit ID: 0x0000271B
Local SNPA: 6cb9.c5cf.da69
IP interface address:
10.10.10.2/24
IPv6 interface address:
fe80::6eb9:c5ff:fecf:da69/64
LDP-ISIS Sync Configured
Holddown timer = 700 seconds, Remaining time = 0 seconds
Level-1 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0001.01
Number of active level-1 adjacencies: 1
Level-1 LSP MTU: 1492
Next IS-IS LAN Level-1 Hello in 4 seconds
R2#
R2#show mpls ldp igp sync
xe11 is up, line protocol is up
LDP configured; LDP-IGP Synchronization enabled.
Session IP Address : 1.1.1.1
Sync status: Achieved
Delay timer: Configured, 55 seconds, Not Running