MPLS CHAPTER 5

MPLS CHAPTER 5
QUESIONS :
16. How do you view the advertised transport address ?
17. What command changes the LDP router-id ?
18. When & how would you change the advertised transport address ?
19. What is MPLS label format ?

SOLUTIONS :
16. How do you view the advertised transport address ?
17. What command changes the LDP router-id ?
18. When & how would you change the advertised transport address ?

follow our diagram:

FOR ROUTER -ID
1. configured
2. highest loopback interface
3. highest physical interface

R2#sh mpls ldp discovery detail
 Local LDP Identifier:
    2.2.2.2:0
    Discovery Sources:
    Interfaces:
        FastEthernet0/0 (ldp): xmit/recv
            Enabled: Interface config
            Hello interval: 5000 ms; Transport IP addr: 2.2.2.2
            LDP Id: 1.1.1.1:0
              Src IP addr: 10.1.12.1; Transport IP addr: 1.1.1.1
              Hold time: 15 sec; Proposed local/peer: 15/15 sec
              Reachable via 1.1.1.1/32
        FastEthernet0/1 (ldp): xmit/recv
            Enabled: Interface config
            Hello interval: 5000 ms; Transport IP addr: 2.2.2.2
            LDP Id: 3.3.3.3:0
              Src IP addr: 10.1.23.3; Transport IP addr: 3.3.3.3
              Hold time: 15 sec; Proposed local/peer: 15/15 sec
              Reachable via 3.3.3.3/32
R2#sh ip route ospf
     1.0.0.0/32 is subnetted, 1 subnets
O       1.1.1.1 [110/11] via 10.1.12.1, 00:07:49, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/11] via 10.1.23.3, 00:07:49, FastEthernet0/1

For R2 local label is 2.2.2.2 remot labels are 1.1.1.1 & 2.2.2.2 which has IGP routes.
for f0/0 transport address 1.1.1.1
for f0/1 transport address 2.2.2.2

Let us traceroute from R1 to R3 loopback :
R1#traceroute 3.3.3.3 source 1.1.1.1

Type escape sequence to abort.
Tracing the route to 3.3.3.3

  1 10.1.12.2 [MPLS: Label 17 Exp 0] 44 msec 60 msec 36 msec
  2 10.1.23.3 40 msec *  64 msec

  if follow the LSP path : 
  
  now create new loopback on R2 make this router-id for MPLS path, and do not advertise
  into the IGP domain.

  Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#int l2
R2(config-if)#ip add 22.2.2.2 255.255.255.255
R2(config-if)#exit
R2(config)#mpls ldp router-id loopback 2 force
and then check the transport-address :
R2#sh mpls ldp discovery detail
 Local LDP Identifier:
    22.2.2.2:0
    Discovery Sources:
    Interfaces:
        FastEthernet0/0 (ldp): xmit/recv
            Enabled: Interface config
            Hello interval: 5000 ms; Transport IP addr: 22.2.2.2
            LDP Id: 1.1.1.1:0
              Src IP addr: 10.1.12.1; Transport IP addr: 1.1.1.1
              Hold time: 15 sec; Proposed local/peer: 15/15 sec
              Reachable via 1.1.1.1/32
        FastEthernet0/1 (ldp): xmit/recv
            Enabled: Interface config
            Hello interval: 5000 ms; Transport IP addr: 22.2.2.2
            LDP Id: 3.3.3.3:0
              Src IP addr: 10.1.23.3; Transport IP addr: 3.3.3.3
              Hold time: 15 sec; Proposed local/peer: 15/15 sec
              Reachable via 3.3.3.3/32

So R-ID and transport address has been changed do the tracerout from the R1-R3 loopback

now you can see it does not follow the LSP(mpls) path. ?????

now advertise loopback into ospf on R2
R2(config)#router ospf 1
R2(config-router)#net 22.2.2.2 0.0.0.0 ar 0
R2(config-router)#
*Mar  1 01:13:55.683: %LDP-5-NBRCHG: LDP Neighbor 3.3.3.3:0 (1) is UP
R2(config-router)#
*Mar  1 01:13:56.951: %LDP-5-NBRCHG: LDP Neighbor 1.1.1.1:0 (2) is UP

R1#
*Mar  1 01:13:47.903: %LDP-5-NBRCHG: LDP Neighbor 22.2.2.2:0 (1) is UP
R1#traceroute 3.3.3.3 source 1.1.1.1

Type escape sequence to abort.
Tracing the route to 3.3.3.3

  1 10.1.12.2 [MPLS: Label 17 Exp 0] 60 msec 40 msec 44 msec
  2 10.1.23.3 56 msec *  48 msec

  now it follow the LSP(mpls path) WoW !!!!
  
  
19. What is MPLS label format ?

mpls label format:
20 bit label : locally significant to router
3 bit Exp = class of service
S bit = defines last label in the label stack
8 bit TTL