The following examples use the FEC filtering parameter.
Consider three MPLS router system devices with an ID 10.66 with the transit device between them.
The following configuration configures the prefix list to allow all /32 addresses, the prefix list to allow 172.16.0.0/16 ge 24 le 24, prefix list to allow172.16.0.0/16 ge 24 le 28, and a prefix list to allow all of the previous FECs.
device(config)# ip prefix filter172_24 permit 172.16.09.0/16 ge 24 le 24 device(config)# ip prefix filter172_24 permit 172.16.09.0/16 ge 24 le 24 device(config)# ip prefix-list filter172_28 permit 172.16.0.0/16 ge 24 le 28 device(config)# ip prefix-list filterAll permit 0.0.0.0/0 ge 32 device(config)# ip prefix-list filterAll permit 172.16.0.0/16 ge 24 le 28
Verify the configuration by using the show mpls ldp command.
device(config)# exit device# show mpls ldp Label Distribution Protocol version 1 LSR ID: 10.44.44.44, using Loopback 1 (deleting stops LDP) Hello interval: Link 5 sec, Targeted 15 sec Hold time value sent in Hellos: Link 15 sec, Targeted 45 sec Keepalive interval: 6 sec, Hold time multiple: 6 intervals Load sharing: 1 Tunnel metric: 0 FEC used for auto discovered peers: current 129, configured 129 Graceful restart: disabled device(config)# do show mpls ldp database Session 10.44.44.44:0 - 10.14.14.14:0 Downstream label database: Label Prefix State 3 10.14.14.14/32 Installed 1024 172.16.8.0/24 Installed 1025 172.16.16.0/24 Installed 1026 172.16.32.0/24 Installed 1027 172.16.64.0/24 Installed 1028 172.16.8.0/28 Installed 1029 172.16.8.16/28 Installed 1030 172.16.8.32/28 Installed 1031 172.16.8.64/28 Installed Upstream label database: Label Prefix 3 10.44.44.44/32 1033 10.66.66.66/32 Session 10.44.44.44:0 - 10.66.66.66:0 Downstream label database: Label Prefix State 3 10.66.66.66/32 Installed Upstream label database: Label Prefix 3 10.44.44.44/32 1024 172.16.8.0/24 1025 172.16.16.0/24 1026 172.16.32.0/24 1027 172.16.64.0/24 1028 172.16.8.0/28 1029 172.16.8.16/28 1030 172.16.8.32/28 1031 172.16.8.64/28 1032 10.14.14.14/32