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