MPLS CHAPTER 3

MPLS CHAPTER 3
QUESTIONS :
8. How does the IGP next hop affect the LSP?
9. Why does LDP advertiese all local IPv4 address to a neighbor ?
10. By default , does the LSP path match the IPv4 path to a network ?
11. What is Liberal Label Retention ?

Solutions:
8. How does the IGP next hop affect the LSP?
9. Why does LDP advertiese all local IPv4 address to a neighbor ?

Follow the same diagram with same address scheme >

--->> IPv4 contorl plan build ospf RIB that is used by MPLS control plan
protocol LDP to build their Lable table (LIB) but data plan is quit different.

let us check RIB and binding tabel (LIB) of R2

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, 00:29:55, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/11] via 10.1.23.3, 00:07:39, FastEthernet0/1
R2#sh mpls ldp bin
R2#sh mpls ldp bindings 3.3.3.3
% Incomplete command.

R2#sh mpls ldp bindings 3.3.3.3 32
  tib entry: 3.3.3.3/32, rev 6
        local binding:  tag: 19
        remote binding: tsr: 1.1.1.1:0, tag: 502
        remote binding: tsr: 3.3.3.3:0, tag: imp-null
R2#

you can see the RIB & LIB of route 3.3.3.3 of R2.

10. By default , does the LSP path match the IPv4 path to a network ?
11. What is Liberal Label Retention ?

LSP is driven by the IGP , We can manupulate with the MPLS-TE.
For a given router the upsteame and downstream labeling is liberal label
retention.

R2#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 - 2.2.2.2.38184
        State: Oper; Msgs sent/rcvd: 40/40; Downstream
        Up time: 00:28:33
        LDP discovery sources:
          FastEthernet0/0, Src IP addr: 10.1.12.1
        Addresses bound to peer LDP Ident:
          10.1.12.1       1.1.1.1
    Peer LDP Ident: 3.3.3.3:0; Local LDP Ident 2.2.2.2:0
        TCP connection: 3.3.3.3.25942 - 2.2.2.2.646
        State: Oper; Msgs sent/rcvd: 21/21; Downstream
        Up time: 00:11:48
        LDP discovery sources:
          FastEthernet0/1, Src IP addr: 10.1.23.3
        Addresses bound to peer LDP Ident:
          10.1.23.3       3.3.3.3

R2#sh mpls ldp bindings 1.1.1.1 32
  tib entry: 1.1.1.1/32, rev 2
        local binding:  tag: 18
        remote binding: tsr: 1.1.1.1:0, tag: imp-null
        remote binding: tsr: 3.3.3.3:0, tag: 22
R2#sh mpls ldp bindings 3.3.3.3 32
  tib entry: 3.3.3.3/32, rev 6
        local binding:  tag: 19
        remote binding: tsr: 1.1.1.1:0, tag: 502
        remote binding: tsr: 3.3.3.3:0, tag: imp-null

R2#sh mpls forwarding-table 1.1.1.1
Local  Outgoing    Prefix            Bytes tag  Outgoing   Next Hop
tag    tag or VC   or Tunnel Id      switched   interface
18     Pop tag     1.1.1.1/32        0          Fa0/0      10.1.12.1
R2#sh mpls forwarding-table 3.3.3.3
Local  Outgoing    Prefix            Bytes tag  Outgoing   Next Hop
tag    tag or VC   or Tunnel Id      switched   interface
19     Pop tag     3.3.3.3/32        0          Fa0/1      10.1.23.3