Label advertisement control configuration example
Network requirements
Two links, Switch A—Switch B—Switch C and Switch A—Switch D—Switch C, exist between subnets 11.1.1.0/24 and 21.1.1.0/24.
Configure label advertisement control, so LDP sets up LSPs only on the link Switch A—Switch B—Switch C to forward traffic between subnets 11.1.1.0/24 and 21.1.1.0/24.
Figure 18: Network diagram
Requirements analysis
To ensure that the LSRs establish LSPs automatically, enable LDP on each LSR.
To establish LDP LSPs, configure a routing protocol to ensure IP connectivity between the LSRs. This example uses OSPF.
To ensure that LDP establishes LSPs only for the routes 11.1.1.0/24 and 21.1.1.0/24, configure LSP generation policies on each LSR.
To ensure that LDP establishes LSPs only over the link Switch A—Switch B—Switch C, configure label advertisement policies as follows:
Switch A advertises only the label mapping for FEC 11.1.1.0/24 to Switch B.
Switch C advertises only the label mapping for FEC 21.1.1.0/24 to Switch B.
Switch D does not advertise label mapping for FEC 21.1.1.0/24 to Switch A. Switch D does not advertise label mapping for FEC 11.1.1.0/24 to Switch C.
Configuration procedure
Configure IP addresses and masks for interfaces, including the loopback interfaces, as shown in Figure 18. (Details not shown.)
Configure OSPF on each switch to ensure IP connectivity between them. (Details not shown.)
Enable MPLS and LDP:
# Configure Switch A.
<SwitchA> system-view [SwitchA] mpls lsr-id 1.1.1.9 [SwitchA] mpls ldp [SwitchA-ldp] quit [SwitchA] interface vlan-interface 2 [SwitchA-Vlan-interface2] mpls enable [SwitchA-Vlan-interface2] mpls ldp enable [SwitchA-Vlan-interface2] quit [SwitchA] interface vlan-interface 6 [SwitchA-Vlan-interface6] mpls enable [SwitchA-Vlan-interface6] mpls ldp enable [SwitchA-Vlan-interface6] quit
# Configure Switch B.
<SwitchB> system-view [SwitchB] mpls lsr-id 2.2.2.9 [SwitchB] mpls ldp [SwitchB-ldp] quit [SwitchB] interface vlan-interface 2 [SwitchB-Vlan-interface2] mpls enable [SwitchB-Vlan-interface2] mpls ldp enable [SwitchB-Vlan-interface2] quit [SwitchB] interface vlan-interface 3 [SwitchB-Vlan-interface3] mpls enable [SwitchB-Vlan-interface3] mpls ldp enable [SwitchB-Vlan-interface3] quit
# Configure Switch C.
<SwitchC> system-view [SwitchC] mpls lsr-id 3.3.3.9 [SwitchC] mpls ldp [SwitchC-ldp] quit [SwitchC] interface vlan-interface 3 [SwitchC-Vlan-interface3] mpls enable [SwitchC-Vlan-interface3] mpls ldp enable [SwitchC-Vlan-interface3] quit [SwitchC] interface vlan-interface 7 [SwitchC-Vlan-interface7] mpls enable [SwitchC-Vlan-interface7] mpls ldp enable [SwitchC-Vlan-interface7] quit
# Configure Switch D.
<SwitchD> system-view [SwitchD] mpls lsr-id 4.4.4.9 [SwitchD] mpls ldp [SwitchD-ldp] quit [SwitchD] interface vlan-interface 6 [SwitchD-Vlan-interface6] mpls enable [SwitchD-Vlan-interface6] mpls ldp enable [SwitchD-Vlan-interface6] quit [SwitchD] interface vlan-interface 7 [SwitchD-Vlan-interface7] mpls enable [SwitchD-Vlan-interface7] mpls ldp enable [SwitchD-Vlan-interface7] quit
Configure LSP generation policies:
# On Switch A, create IP prefix list switcha, and configure LDP to use only the routes permitted by the prefix list to establish LSPs.
[SwitchA] ip prefix-list switcha index 10 permit 11.1.1.0 24 [SwitchA] ip prefix-list switcha index 20 permit 21.1.1.0 24 [SwitchA] mpls ldp [SwitchA-ldp] lsp-trigger prefix-list switcha [SwitchA-ldp] quit
# On Switch B, create IP prefix list switchb, and configure LDP to use only the routes permitted by the prefix list to establish LSPs.
[SwitchB] ip prefix-list switchb index 10 permit 11.1.1.0 24 [SwitchB] ip prefix-list switchb index 20 permit 21.1.1.0 24 [SwitchB] mpls ldp [SwitchB-ldp] lsp-trigger prefix-list switchb [SwitchB-ldp] quit
# On Switch C, create IP prefix list switchc, and configure LDP to use only the routes permitted by the prefix list to establish LSPs.
[SwitchC] ip prefix-list switchc index 10 permit 11.1.1.0 24 [SwitchC] ip prefix-list switchc index 20 permit 21.1.1.0 24 [SwitchC] mpls ldp [SwitchC-ldp] lsp-trigger prefix-list switchc [SwitchC-ldp] quit
# On Switch D, create IP prefix list switchd, and configure LDP to use only the routes permitted by the prefix list to establish LSPs.
[SwitchD] ip prefix-list switchd index 10 permit 11.1.1.0 24 [SwitchD] ip prefix-list switchd index 20 permit 21.1.1.0 24 [SwitchD] mpls ldp [SwitchD-ldp] lsp-trigger prefix-list switchd [SwitchD-ldp] quit
Configure label advertisement policies:
# On Switch A, create an IP prefix list prefix-to-b that permits subnet 11.1.1.0/24. Switch A uses this list to filter FEC-label mappings advertised to Switch B.
[SwitchA] ip prefix-list prefix-to-b index 10 permit 11.1.1.0 24
# On Switch A, create an IP prefix list peer-b that permits 2.2.2.9/32. Switch A uses this list to filter peers.
[SwitchA] ip prefix-list peer-b index 10 permit 2.2.2.9 32
# On Switch A, configure a label advertisement policy to advertise only the label mapping for FEC 11.1.1.0/24 to Switch B.
[SwitchA] mpls ldp [SwitchA-ldp] advertise-label prefix-list prefix-to-b peer peer-b [SwitchA-ldp] quit
# On Switch C, create an IP prefix list prefix-to-b that permits subnet 21.1.1.0/24. Switch C uses this list to filter FEC-label mappings advertised to Switch B.
[SwitchC] ip prefix-list prefix-to-b index 10 permit 21.1.1.0 24
# On Switch C, create an IP prefix list peer-b that permits 2.2.2.9/32. Switch C uses this list to filter peers.
[SwitchC] ip prefix-list peer-b index 10 permit 2.2.2.9 32
# On Switch C, configure a label advertisement policy to advertise only the label mapping for FEC 21.1.1.0/24 to Switch B.
[SwitchC] mpls ldp [SwitchC-ldp] advertise-label prefix-list prefix-to-b peer peer-b [SwitchC-ldp] quit
# On Switch D, create an IP prefix list prefix-to-a that denies subnet 21.1.1.0/24. Switch D uses this list to filter FEC-label mappings to be advertised to Switch A.
[SwitchD] ip prefix-list prefix-to-a index 10 deny 21.1.1.0 24 [SwitchD] ip prefix-list prefix-to-a index 20 permit 0.0.0.0 0 less-equal 32
# On Switch D, create an IP prefix list peer-a that permits 1.1.1.9/32. Switch D uses this list to filter peers.
[SwitchD] ip prefix-list peer-a index 10 permit 1.1.1.9 32
# On Switch D, create an IP prefix list prefix-to-c that denies subnet 11.1.1.0/24. Switch D uses this list to filter FEC-label mappings to be advertised to Switch C.
[SwitchD] ip prefix-list prefix-to-c index 10 deny 11.1.1.0 24 [SwitchD] ip prefix-list prefix-to-c index 20 permit 0.0.0.0 0 less-equal 32
# On Switch D, create an IP prefix list peer-c that permits subnet 3.3.3.9/32. Switch D uses this list to filter peers.
[SwitchD] ip prefix-list peer-c index 10 permit 3.3.3.9 32
# On Switch D, configure a label advertisement policy, so Switch D does not advertise label mappings for FEC 21.1.1.0/24 to Switch A, and does not advertise label mappings for FEC 11.1.1.0/24 to Switch C.
[SwitchD] mpls ldp [SwitchD-ldp] advertise-label prefix-list prefix-to-a peer peer-a [SwitchD-ldp] advertise-label prefix-list prefix-to-c peer peer-c [SwitchD-ldp] quit
Verifying the configuration
# Display LDP LSP information on each switch.
[SwitchA] 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 Vlan-int2
1276/1276 10.1.1.2 Vlan-int2
[SwitchB] display mpls ldp lsp
Status Flags: * - stale, L - liberal
Statistics:
FECs: 2 Ingress LSPs: 2 Transit LSPs: 2 Egress LSPs: 0
FEC In/Out Label Nexthop OutInterface
11.1.1.0/24 -/1277 10.1.1.1 Vlan-int2
1277/1277 10.1.1.1 Vlan-int2
21.1.1.0/24 -/1149 20.1.1.2 Vlan-int3
1276/1149 20.1.1.2 Vlan-int3
[SwitchC] 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 20.1.1.1 Vlan-int3
1148/1277 20.1.1.1 Vlan-int3
21.1.1.0/24 1149/-
-/1276(L)
-/1150(L)
[SwitchD] display mpls ldp lsp
Status Flags: * - stale, L - liberal
Statistics:
FECs: 2 Ingress LSPs: 0 Transit LSPs: 0 Egress LSPs: 2
FEC In/Out Label Nexthop OutInterface
11.1.1.0/24 1151/-
-/1277(L)
21.1.1.0/24 1150/-
The output shows that Switch A and Switch C have received FEC-label mappings only from Switch B. Switch B has received FEC-label mappings from both Switch A and Switch C. Switch D does not receive FEC-label mappings from Switch A or Switch C. LDP has set up an LSP only over the link Switch A—Switch B—Switch C.
# Test the connectivity of the LDP LSP from Switch A to Switch C.
[SwitchA] ping mpls -a 11.1.1.1 ipv4 21.1.1.0 24 MPLS Ping FEC: 21.1.1.0/24 : 100 data bytes 100 bytes from 20.1.1.2: Sequence=1 time=1 ms 100 bytes from 20.1.1.2: Sequence=2 time=1 ms 100 bytes from 20.1.1.2: Sequence=3 time=8 ms 100 bytes from 20.1.1.2: Sequence=4 time=2 ms 100 bytes from 20.1.1.2: Sequence=5 time=1 ms --- FEC: 21.1.1.0/24 ping statistics --- 5 packets transmitted, 5 packets received, 0.0% packet loss round-trip min/avg/max = 1/2/8 ms
# Test the connectivity of the LDP LSP from Switch C to Switch A.
[SwitchC] ping mpls -a 21.1.1.1 ipv4 11.1.1.0 24 MPLS Ping FEC: 11.1.1.0/24 : 100 data bytes 100 bytes from 10.1.1.1: Sequence=1 time=1 ms 100 bytes from 10.1.1.1: Sequence=2 time=1 ms 100 bytes from 10.1.1.1: Sequence=3 time=1 ms 100 bytes from 10.1.1.1: Sequence=4 time=1 ms 100 bytes from 10.1.1.1: Sequence=5 time=1 ms --- FEC: 11.1.1.0/24 ping statistics --- 5 packets transmitted, 5 packets received, 0.0% packet loss round-trip min/avg/max = 1/1/1 ms