CCIE SP WBv3 - Lab#4 XR1 mpls forwarding

Hello,

I see the XR1 doen's send label to R5 and XR2 with BGP redistribution into ISIS.

 

XR1

===================

16013  16          10.0.0.4/32        Gi0/1/0/0.193 10.0.193.3      4649

16015  Pop         10.0.0.3/32        Gi0/1/0/0.193 10.0.193.3      0

16016  20          10.0.0.1/32        Gi0/1/0/0.193 10.0.193.3      19078

====================


router isis 1000


 address-family ipv4 unicast

  redistribute bgp 1000



================


10.0.0.1/32, rev 0

        No local binding

        Remote bindings: (3 peers)

            Peer                Label

            -----------------   --------

            10.0.0.2:0          29

            10.0.0.5:0          18

            10.0.0.20:0         16010




R5 doesn't receive a LABEL but has LDP neig. Why this ?



R5#sh mpls forwarding-table | inc No L

18         No Label   10.0.0.1/32      0             Fa0/0.195  10.0.195.19

25         No Label   10.0.0.3/32      0             Fa0/0.195  10.0.195.19

30         No Label   10.0.0.4/32      0             Fa0/0.195  10.0.195.19





R5#sh mpls  ldp  neighbor

    Peer LDP Ident: 10.0.0.2:0; Local LDP Ident 10.0.0.5:0

        TCP connection: 10.0.0.2.646 - 10.0.0.5.19365

        State: Oper; Msgs sent/rcvd: 47/45; Downstream

        Up time: 00:16:06

        LDP discovery sources:

          FastEthernet0/0.25, Src IP addr: 10.0.25.2

        Addresses bound to peer LDP Ident:

          10.0.0.2        10.0.25.2       10.0.220.2

    Peer LDP Ident: 10.0.0.20:0; Local LDP Ident 10.0.0.5:0

        TCP connection: 10.0.0.20.12467 - 10.0.0.5.646

        State: Oper; Msgs sent/rcvd: 49/48; Downstream

        Up time: 00:16:01

        LDP discovery sources:

          FastEthernet0/0.205, Src IP addr: 10.0.205.20

        Addresses bound to peer LDP Ident:

          10.0.0.20       10.0.205.20     10.0.220.20     10.19.20.20

    Peer LDP Ident: 10.0.0.19:0; Local LDP Ident 10.0.0.5:0

        TCP connection: 10.0.0.19.28259 - 10.0.0.5.646

        State: Oper; Msgs sent/rcvd: 31/28; Downstream

        Up time: 00:11:52

        LDP discovery sources:

          FastEthernet0/0.195, Src IP addr: 10.0.195.19

        Addresses bound to peer LDP Ident:

          10.0.0.19       10.0.193.19     10.0.195.19     10.19.20.19




Comments

  • From Cisco TAC:

     

    CSCtt22999 vpnv4 prefix fails to program with connected primary and BGP backup path 
    Externally found severe (Sev2) bug: R-Resolved 
    Integrated in 4.2.0

    <B>Symptom:</B>
    FIB traceback and forwarding error is seen for an extranet connected route.


    <B>Conditions:</B>
    (1) Connected route is redistributed into BGP in the source VRF.
    (2) The connected route is exported to another VRF (as extranet route)
    (3) The extranet route also has an imported IBGP path
    (4) Backup path installation (PIC) is configured on the extranet VRF
    (5) BGP calculates and installs a backup path for the extranet connected route

    <B>Recovery:</B>
    Backup path calculation should be prevented for extranet
    Connected routes using "additional-paths selection route-policy".


    <B>Workaround:</B>
    Backup path calculation should be prevented for extranet
    Connected routes using "additional-paths selection route-policy".


    <B>Further Problem Description:</B>
    FIB cannot handle backup paths when the bestpath has a
    non-recursive nexthop. Use the add-path selection RPL
    to control which prefixes are allowed to have a backup path.

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