Example for Configuring IS-IS Fast Convergence
Networking Requirements
As shown in Figure 7-38, two routers are connected through a Layer 2 switch. The two routers communicate with each other through the IS-IS protocol. The convergence speed of the two routers needs to be improved.
Configuration Roadmap
The configuration roadmap is as follows:
Configure the IP addresses of interfaces and the IS-IS route-policy on each router so that routes on the two routers are reachable.
Configure BFD sessions on RouterA and RouterB to improve the link fault detection speed of the routers.
Set the time parameters of fast convergence on RouterA and RouterB to implement IS-IS fast convergence.
Procedure
- Configure IP addresses for interfaces on each router.
# Configure RouterA.
<Huawei> system-view
[Huawei] sysname RouterA
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] ip address 10.1.1.1 24
[RouterA-GigabitEthernet1/0/0] quit
The configuration of RouterB is similar to the configuration of RouterA, and is not mentioned here.
- Configure basic IS-IS functions.
# Configure RouterA.
[RouterA] isis 1
[RouterA-isis-1] is-level level-2
[RouterA-isis-1] network-entity 10.0000.0000.0001.00
[RouterA-isis-1] quit
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] isis enable 1
[RouterA-GigabitEthernet1/0/0] quit
# Configure RouterB.
[RouterB] isis 1
[RouterB-isis-1] is-level level-2
[RouterB-isis-1] network-entity 10.0000.0000.0002.00
[RouterB-isis-1] quit
[RouterB] interface gigabitethernet 1/0/0
[RouterB-GigabitEthernet1/0/0] isis enable 1
[RouterB-GigabitEthernet1/0/0] quit
- Configure BFD.
# Configure RouterA.
[RouterA] bfd
[RouterA-bfd] quit
[RouterA] bfd atob bind peer-ip 10.1.1.2 interface gigabitethernet 1/0/0
[RouterA-bfd-session-atob] discriminator local 1
[RouterA-bfd-session-atob] discriminator remote 2
[RouterA-bfd-session-atob] commit
[RouterA-bfd-session-atob] quit
[RouterA] interface gigabitethernet 1/0/0
[RouterA-GigabitEthernet1/0/0] isis bfd static
[RouterA-GigabitEthernet1/0/0] quit
# Configure RouterB.
[RouterB] bfd
[RouterB-bfd] quit
[RouterB] bfd btoa bind peer-ip 10.1.1.1 interface gigabitethernet 1/0/0
[RouterB-bfd-session-btoa] discriminator local 2
[RouterB-bfd-session-btoa] discriminator remote 1
[RouterB-bfd-session-btoa] commit
[RouterB-bfd-session-btoa] quit
[RouterB] interface gigabitethernet 1/0/0
[RouterB-GigabitEthernet1/0/0] isis bfd static
[RouterB-GigabitEthernet1/0/0] quit
- Set the time parameters of fast convergence.
# Configure RouterA.
[RouterA] isis 1
[RouterA-isis-1] flash-flood
[RouterA-isis-1] timer spf 1 20 100
[RouterA-isis-1] timer lsp-generation 1 1 120
[RouterA-isis-1] quit
# Configure RouterB.
[RouterB] isis 1
[RouterB-isis-1] flash-flood
[RouterB-isis-1] timer spf 1 20 100
[RouterB-isis-1] timer lsp-generation 1 1 120
[RouterB-isis-1] quit
In IS-IS, if the LSDB changes, routes are calculated and a new LSP is generated to report this change. Frequent route calculations consume a lot of system resources and decrease the system performance. Delaying SPF calculation and LSP generation and speeding up LSP flooding can improve the efficiency in route calculation and reduce the consumption of system resources.
The flash-flood command enables LSP fast flooding to speed up IS-IS network convergence.
The timer spf command sets the interval for SPF calculation. The default interval is 5 seconds.
The timer lsp-generation command sets the delay in generating an LSP. The default interval is 2 seconds.
- Verify the configuration.
# Run the shutdown command on GE1/0/0 of RouterB to shut down the link.
[RouterB] interface gigabitethernet 1/0/0
[RouterB-GigabitEthernet1/0/0] shutdown
# View the information about neighbors of RouterA.
<RouterA> display isis peer
INformation about neighbors of RouterA does not exist.
When BFD detects that the link goes Down, it notifies the routing management (RM) module immediately. IS-IS then deletes the neighbor relationship immediately and triggers route calculation. This implements fast convergence of the network.
Configuration Files
Configuration file of RouterA
#
sysname RouterA
#
bfd
#
isis 1
is-level level-2
timer lsp-generation 1 1 120 level-1
timer lsp-generation 1 1 120 level-2
flash-flood level-1
flash-flood level-2
network-entity 10.0000.0000.0001.00
timer spf 1 20 100
#
interface GigabitEthernet1/0/0
ip address 10.1.1.1 255.255.255.0
isis enable 1
isis bfd static
#
bfd atob bind peer-ip 10.1.1.2 interface GigabitEthernet1/0/0
discriminator local 1
discriminator remote 2
commit
#
return
Configuration file of RouterB
#
sysname RouterB
#
bfd
#
isis 1
is-level level-2
timer lsp-generation 1 1 120 level-1
timer lsp-generation 1 1 120 level-2
flash-flood level-1
flash-flood level-2
network-entity 10.0000.0000.0002.00
timer spf 1 20 100
#
interface GigabitEthernet1/0/0
ip address 10.1.1.2 255.255.255.0
isis enable 1
isis bfd static
#
bfd btoa bind peer-ip 10.1.1.1 interface GigabitEthernet1/0/0
discriminator local 2
discriminator remote 1
commit
#
return