MPLS

Basic Congiruation

mpls ldp router-id Loopback0 [force]
mpls label range 200 299
interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!
interface Ethernet0/0
 ip address 10.0.12.2 255.255.255.0
 mpls ip
!
interface Ethernet0/1
 ip address 10.0.23.2 255.255.255.0
 mpls ip
!

Load Sharing

When routing by FIB, the router uses source and destination address combination to determine the next hop. This behavior can be changed by the following command.

(config)# ip load-sharing per-packet

When routing by LFIB, the router determine the next hop depending on the payload. If the payload is IPv4 or IPv6 packet, it is routed by the source and destination address combination. If the payload is other packet type, it is routed by the lastest tag in the MPLS tagging.

Advanced Fetaure

PHP

The edge router will bind implicit null to the connected router to let the neighbor pop the tag so the edge router can lookup FIB directly. If this is not set, the router needs to lookup LFIB to pop the tag and then lookup FIB to do the route, which is very inefficient.

TTL Propagation

Use the following command to disable TTL propagation which is the default.

IOU2(config)#no mpls ip propagate-ttl

Explicit Null

The following command makes the router send explicit null(0) to other routers rather than implicit null(3) value which is the default.

IOU2(config)#mpls ldp explicit-null

Advertise to Specific Routers

! Disable advertising to all the neighbors
(config)# no mpls ldp advertise-labels
! Define which neigbhors to advertise
(config)# mpls ldp advertise-labels [for prefix-access-list [to peer-access-list]]

Command

Change the label protocol

(config)# mpls label protocol {ldp | tdp}
(config-if)# mpls label protocol {ldp | tdp | both}

IOU2#sh mpls ldp bindings
  lib entry: 1.1.1.1/32, rev 2
        local binding:  label: 16
        remote binding: lsr: 1.1.1.1:0, label: imp-null
        remote binding: lsr: 3.3.3.3:0, label: 16
  lib entry: 2.2.2.2/32, rev 4
        local binding:  label: imp-null
        remote binding: lsr: 1.1.1.1:0, label: 16
        remote binding: lsr: 3.3.3.3:0, label: 17
  lib entry: 3.3.3.3/32, rev 6
        local binding:  label: 17
        remote binding: lsr: 1.1.1.1:0, label: 17
        remote binding: lsr: 3.3.3.3:0, label: imp-null
  lib entry: 10.0.12.0/24, rev 8
        local binding:  label: imp-null
        remote binding: lsr: 1.1.1.1:0, label: imp-null
        remote binding: lsr: 3.3.3.3:0, label: 18
  lib entry: 10.0.23.0/24, rev 10
        local binding:  label: imp-null
        remote binding: lsr: 1.1.1.1:0, label: 18
        remote binding: lsr: 3.3.3.3:0, label: imp-null

IOU2#sh mpls forwarding-table
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop
Label      Label      or Tunnel Id     Switched      interface
16         Pop Label  1.1.1.1/32       0             Et0/0      10.0.12.1
17         Pop Label  3.3.3.3/32       0             Et0/1      10.0.23.3

IOU2#sh mpls ldp neighbor
    Peer LDP Ident: 1.1.1.1:0; Local LDP Ident 2.2.2.2:0
        TCP connection: 1.1.1.1.646 - 2.2.2.2.31656
        State: Oper; Msgs sent/rcvd: 223/224; Downstream
        Up time: 03:09:03
        LDP discovery sources:
          Ethernet0/0, Src IP addr: 10.0.12.1
        Addresses bound to peer LDP Ident:
          10.0.12.1       1.1.1.1
    Peer LDP Ident: 3.3.3.3:0; Local LDP Ident 2.2.2.2:0
        TCP connection: 3.3.3.3.28092 - 2.2.2.2.646
        State: Oper; Msgs sent/rcvd: 225/225; Downstream
        Up time: 03:08:52
        LDP discovery sources:
          Ethernet0/1, Src IP addr: 10.0.23.3
        Addresses bound to peer LDP Ident:
          10.0.23.3       3.3.3.3

sh mpls ldp parameters