137
Configuring IS-IS route filtering
You can use an ACL, IP prefix list, or routing policy to filter routes calculated using received LSPs and
routes redistributed from other routing protocols.
Filtering routes calculated from received LSPs
IS-IS saves LSPs received from neighbors in the LSDB, uses the SPF algorithm to calculate the shortest path
tree with itself as the root, and installs the routes to the IS-IS routing table. IS-IS installs the optimal routes
to the IP routing table.
Perform this task to filter calculated routes. Only routes that are not filtered can be added to the IP routing
table. The filtered routes retain in the IS-IS routing table and can be advertised to neighbors.
To filter routes calculated using received LSPs:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter IS-IS IPv4 unicast
address family view.
1.
isis
[
process-id
] [
vpn-instance
vpn-instance-name
]
2.
cost-style
{
wide
|
wide-compatible
}
3.
address-family ipv4
[
unicast
]
N/A
3.
Filter routes calculated
using received LSPs.
filter-policy
{
acl-number
|
prefix-list
prefix-list-name
|
route-policy
route-policy-name
}
import
By default, IS-IS route
filtering is not configured.
Filtering redistributed routes
IS-IS can redistribute routes from other routing protocols or other IS-IS processes, add them to the IS-IS
routing table, and advertise them in LSPs.
Perform this task to filter redistributed routes. Only routes that are not filtered can be added to the IS-IS
routing table and advertised to neighbors.
To filter redistributed routes:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter IS-IS IPv4 unicast
address family view.
1.
isis
[
process-id
] [
vpn-instance
vpn-instance-name
]
2.
cost-style
{
wide
|
wide-compatible
}
3.
address-family ipv4
[
unicast
]
N/A
3.
Filter routes redistributed from
other routing protocols or IS-IS
processes.
filter-policy
{
acl-number
|
prefix-list
prefix-list-name
|
route-policy
route-policy-name
}
export
[
protocol
[
process-id
] ]
By default, IS-IS route
filtering is not configured.
Configuring IS-IS route leaking
Perform this task to control route advertisement (route leaking) between Level-1 and Level-2.
