4000 Router Series MPLS Configuration Guide

# On Router C, create an IP prefix list prefix-to-b that permits subnet 21.1.1.0/24. Router C uses

this list to filter FEC-label mappings advertised to Router B.

[RouterC] ip prefix-list prefix-to-b index 10 permit 21.1.1.0 24

# On Router C, create an IP prefix list peer-b that permits 2.2.2.9/32. Router C uses this list to filter

peers.

[RouterC] ip prefix-list peer-b index 10 permit 2.2.2.9 32

# On Router C, configure a label advertisement policy to advertise only the label mapping for FEC

21.1.1.0/24 to Router B.

[RouterC] mpls ldp

[RouterC-ldp] advertise-label prefix-list prefix-to-b peer peer-b

[RouterC-ldp] quit

# On Router D, create an IP prefix list prefix-to-a that denies subnet 21.1.1.0/24. Router D uses

this list to filter FEC-label mappings to be advertised to Router A.

[RouterD] ip prefix-list prefix-to-a index 10 deny 21.1.1.0 24

[RouterD] ip prefix-list prefix-to-a index 20 permit 0.0.0.0 0 less-equal 32

# On Router D, create an IP prefix list peer-a that permits 1.1.1.9/32. Router D uses this list to filter

peers.

[RouterD] ip prefix-list peer-a index 10 permit 1.1.1.9 32

# On Router D, create an IP prefix list prefix-to-c that denies subnet 11.1.1.0/24. Router D uses

this list to filter FEC-label mappings to be advertised to Router C.

[RouterD] ip prefix-list prefix-to-c index 10 deny 11.1.1.0 24

[RouterD] ip prefix-list prefix-to-c index 20 permit 0.0.0.0 0 less-equal 32

# On Router D, create an IP prefix list peer-c that permits subnet 3.3.3.9/32. Router D uses this list

to filter peers.

[RouterD] ip prefix-list peer-c index 10 permit 3.3.3.9 32

# On Router D, configure a label advertisement policy, so Router D does not advertise label

mappings for FEC 21.1.1.0/24 to Router A, and does not advertise label mappings for FEC

11.1.1.0/24 to Router C.

[RouterD] mpls ldp

[RouterD-ldp] advertise-label prefix-list prefix-to-a peer peer-a

[RouterD-ldp] advertise-label prefix-list prefix-to-c peer peer-c

[RouterD-ldp] quit

Verifying the configuration

# Execute the display mpls ldp lsp command on each router to view the LDP LSP information.

[RouterA] display mpls ldp lsp

Status Flags: * - stale, L - liberal

Statistics:

FECs: 2 Ingress LSPs: 1 Transit LSPs: 1 Egress LSPs: 1

FEC In/Out Label Nexthop OutInterface

11.1.1.0/24 1277/-

-/1151(L)

-/1277(L)

21.1.1.0/24 -/1276 10.1.1.2 S2/0

1276/1276 10.1.1.2 S2/0

[RouterB] display mpls ldp lsp

Status Flags: * - stale, L - liberal