Example: Configuring IS-IS Route Leaking From a Level 2 Area to a Level 1 Area
This example shows how to leak prefixes in an IS-IS network from a Level 2 area to a Level 1 area.
Requirements
No special configuration beyond device initialization is required before configuring this example.
Overview
Every routing protocol passes routing information up or down the routing hierarchy. This bidirectional flow of routing information is known as route leaking.
By default, IS-IS protocol leaks routing information from a Level 1 area to a Level 2 area. However, to leak routing information from a Level 2 area to a Level 1 area, an export policy must be explicitly configured.
Topology
In this example, Devices R3 and R4 are configured in a Level 2 area. Devices R5, R6, and R7 are configured in a Level 1 area.
Figure 1 shows the topology used in this example.
Figure 1: Route Leaking From a Level 2 Area to a Level 1 Area
Configuration
Configuring Route Leaking From a Level 2 Area to a Level 1 Area
CLI Quick Configuration
To quickly configure route leaking from a Level 2 area to a Level 1 area, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.
Device R3
Device R4
Device R5
Device R6
Device R7
Step-by-Step Procedure
Configuring Route Leaking From a Level 2 Area to a Level 1 Area
Step-by-Step Procedure
The following example requires that you navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.
To configure route leaking from a Level 2 area to a Level 1 area:
- Configure the network interfaces.
Enable IS-IS on the interfaces by including the ISO address family on each interface.
[edit interfaces]user@R3# set fe-1/2/0 unit 0 description to-R4user@R3# set fe-1/2/0 unit 0 family inet address 10.0.0.17/30user@R3# set fe-1/2/0 unit 0 family isouser@R3# set fe-1/2/1 unit 0 description to-R5user@R3# set fe-1/2/1 unit 0 family inet address 10.0.0.21/30user@R3# set fe-1/2/1 unit 0 family isoSimilarly, configure other routers.
- Configure two loopback interface addresses.
One address is for IPv4, and the other address is to enable the router to form adjacencies with other routers in the area.
[edit interfaces lo0 unit 0]user@R3# set family inet address 192.168.0.3/32user@R3# set family iso address 49.0001.0192.0168.0003.00 - Specify the IS-IS level on a per-interface basis.[edit protocols isis interface]user@R3# set fe-1/2/0.0 level 1 disableuser@R3# set fe-1/2/1.0 level 1 disableuser@R3# set lo0.0 level 1 disable
- Configure a route leaking policy on the routers configured
in the Level 2 area to leak routes into the Level 1 area.[edit policy-options policy-statement leak-L2-to-L1] user@R3# set from route-filter 192.168.0.0/24 orlongeruser@R3# set from protocol isisuser@R3# set from level 2user@R3# set to protocol isisuser@R3# set to level 1user@R3# set then accept[edit protocols isis]user@R3# set export leak-L2-to-L1
Similarly, configure Router R4.
Results
From configuration mode, confirm your configuration by entering the show interfaces, show protocols isis, and show policy-options commands.
If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.
user@R3# show interfacesfe-1/2/0 {
unit 0 {
description to-R4;
family inet {
address 10.0.0.17/30;
}
family iso;
}
}
fe-1/2/1 {
unit 0 {
description to-R5;
family inet {
address 10.0.0.21/30;
}
family iso;
}
}
lo0 {
unit 0 {
family inet {
address 192.168.0.3/32;
}
family iso {
address 49.0001.0192.0168.0003.00;
}
}
}user@R3# show protocols isisexport leak-L2-to-L1;
interface fe-1/2/0.0 {
level 1 disable;
}
interface fe-1/2/1.0 {
level 1 disable;
}
interface lo0.0 {
level 1 disable;
}
user@R3# show policy-optionspolicy-statement leak-L2-to-L1 {
from {
protocol isis;
level 2;
route-filter 192.168.0.0/24 orlonger;
}
to {
protocol isis;
level 1;
}
then accept;
}Similarly, confirm the configuration on all other routers. If you are done configuring the routers, enter commit from configuration mode.
Verification
Verifying Route Leaking From a Level 2 Area to a Level 1 Area
Purpose
Verify that IS-IS leaks routes from a Level 2 area to a Level 1 area.
Action
To verify that route leaking is taking place, use the following commands:
- show isis adjacency (to verify that the IS-IS network is up and adjacencies have been established)
- show isis database detail (to verify the presence of leaked routes)
- From operational mode on Router R3, run the show isis adjacency command.
user@R3> show isis adjacencyInterface System L State Hold (secs) SNPA fe-1/2/0.0 R4 2 Up 7 0:5:85:8f:94:bd fe-1/2/1.0 R5 2 Up 7 0:5:85:8f:94:bd
The output verifies that the interfaces on Router R3 are up and have established adjacencies with the connecting interfaces on Routers R4 and R5. If you don’t see the interfaces being functional, see the Results section for troubleshooting your configuration.
- From operational mode on Router R3, run the show isis database detail command.
user@R3> show isis database detailIS-IS level 1 link-state database: R3.00-00 Sequence: 0x19, Checksum: 0x3453, Lifetime: 1078 secs IP prefix: 192.168.0.4/32 Metric: 10 Internal Down IP prefix: 192.168.0.5/32 Metric: 10 Internal Down IP prefix: 192.168.0.6/32 Metric: 20 Internal Down IP prefix: 192.168.0.7/32 Metric: 20 Internal Down IS-IS level 2 link-state database: R3.00-00 Sequence: 0x1c, Checksum: 0xc657, Lifetime: 1078 secs IS neighbor: R4.02 Metric: 10 IS neighbor: R5.02 Metric: 10 IP prefix: 10.0.0.16/30 Metric: 10 Internal Up IP prefix: 10.0.0.20/30 Metric: 10 Internal Up IP prefix: 192.168.0.3/32 Metric: 0 Internal Up R4.00-00 Sequence: 0x19, Checksum: 0xea13, Lifetime: 1076 secs IS neighbor: R4.02 Metric: 10 IS neighbor: R5.03 Metric: 10 IP prefix: 10.0.0.16/30 Metric: 10 Internal Up IP prefix: 10.0.0.24/30 Metric: 10 Internal Up IP prefix: 192.168.0.4/32 Metric: 0 Internal Up R4.02-00 Sequence: 0x17, Checksum: 0xecab, Lifetime: 1076 secs IS neighbor: R3.00 Metric: 0 IS neighbor: R4.00 Metric: 0 R5.00-00 Sequence: 0x12, Checksum: 0xf4e5, Lifetime: 1076 secs IS neighbor: R5.02 Metric: 10 IS neighbor: R5.03 Metric: 10 IP prefix: 10.0.0.20/30 Metric: 10 Internal Up IP prefix: 10.0.0.24/30 Metric: 10 Internal Up IP prefix: 10.0.0.28/30 Metric: 10 Internal Up IP prefix: 10.0.0.32/30 Metric: 20 Internal Up IP prefix: 10.0.0.36/30 Metric: 10 Internal Up IP prefix: 192.168.0.5/32 Metric: 0 Internal Up IP prefix: 192.168.0.6/32 Metric: 10 Internal Up IP prefix: 192.168.0.7/32 Metric: 10 Internal Up R5.02-00 Sequence: 0xb, Checksum: 0x2d74, Lifetime: 1076 secs IS neighbor: R3.00 Metric: 0 IS neighbor: R5.00 Metric: 0 R5.03-00 Sequence: 0xb, Checksum: 0x6c32, Lifetime: 1076 secs IS neighbor: R4.00 Metric: 0 IS neighbor: R5.00 Metric: 0
The Down keyword identifies the routes that have successfully leaked from the Level 2 area to the Level 1 area.
Meaning
Route leaking from a Level 2 to a Level 1 area is functioning as expected.
