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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, and uses the SPF algorithm to calculate the
shortest path tree with itself as the root. IS-IS installs the calculated routes to the IS-IS routing table
and 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:
1. Enter system view.
N/A
2. Enter IS-IS IPv4
unicast address
family view.
a isis [ process-id ] [ vpn-instance
vpn-instance-name ]
b address-family ipv4 [ unicast ]
N/A
3. Filter routes
calculated using
received LSPs.
filter-policy
{ ipv4-acl-number |
prefix-list
prefix-list-name |
route-policy
route-policy-name }
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:
1. Enter system view.
system-view
N/A
2. Enter IS-IS IPv4 unicast
address family view.
a isis [ process-id ] [ vpn-instance
vpn-instance-name ]
b address-family ipv4 [ unicast ]
N/A
3. Filter routes redistributed
from other routing protocols
or IS-IS processes.
filter-policy
{ ipv4-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.
You can configure IS-IS to advertise routes from Level-2 to Level-1, and to not advertise routes from
Level-1 to Level-2.
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