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[Junos] Which route table is used by BGP to resolve protocol next-hop for NG-MVPN?

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Article ID: KB28667 KB Last Updated: 03 Jan 2014Version: 1.0
Summary:

The Border Gateway Protocol (BGP) uses different tables to resolve protocol next-hop for different applications. In a normal BGP application like IPv4, the prefix is learned in the default table inet.0.  BGP will try to resolve its protocol next-hop in the table inet.3 first;  if fails, it will resolve in the table inet.0. However, in L3VPN and L2VPN applications, BGP will resolve its protocol next-hop in the table inet.3 only.

This article explains which route table is used by BGP to resolve the  protocol next-hop for NG-MVPN (v4 and v6), and gives two case examples.

Symptoms:

This article explains which route table is used by BGP to resolve protocol next-hop for NG-MVPN (v4 and v6).

Cause:
 
Solution:
Case 1:  BGP protocol next-hop exists in both table inet.0 and inet.3.

<----Route resolution is kept by default.
> show configuration routing-options resolution | display inheritance no-comments 

{MASTER}
<----As a BGP protocol next-hop, 10.233.32.17 exists in both table inet.0 and inet.3.
> show route 10.233.32.17/32 exact 

inet.0: 526772 destinations, 1047867 routes (526770 active, 0 holddown, 2 hidden)
+ = Active Route, - = Last Active, * = Both

10.233.32.17/32    *[IS-IS/18] 29w5d 12:50:45, metric 2400
                      to 10.55.36.148 via ge-0/0/0.0
                    > to 10.55.36.150 via ge-1/0/0.0

inet.3: 5663 destinations, 6709 routes (1044 active, 0 holddown, 5663 hidden)
+ = Active Route, - = Last Active, * = Both

10.233.32.17/32    *[LDP/9] 29w5d 12:50:02, metric 2400
                      to 10.55.36.148 via ge-0/0/0.0, label-switched-path LSP:a2b
                    > to 10.55.36.150 via ge-1/0/0.0, label-switched-path LSP:a2c
                      to 10.55.36.150 via ge-1/0/0.0, label-switched-path LSP:a2b
                      to 10.55.36.148 via ge-0/0/0.0, label-switched-path LSP:a2c

{MASTER}
<----BGP uses table inet.3 to resolve protocol next-hop 10.233.32.17 for NG-MVPN prefix.
> show route table bgp.mvpn.0 match-prefix 7:10.233.38.59:5006:4788:32:10.0.194.198:32:239.192.100.230/240 extensive 

bgp.mvpn.0: 833 destinations, 1666 routes (833 active, 0 holddown, 0 hidden)
7:10.233.38.59:5006:4788:32:10.0.194.198:32:239.192.100.230/240 (2 entries, 0 announced)
        *BGP    Preference: 170/-101
                Next hop type: Indirect
                Address: 0x119725f8
                Next-hop reference count: 1544
                Source: 10.233.32.17
                Protocol next hop: 10.233.32.17
                Indirect next hop: 2 no-forward
                State: 
                Local AS:  4788 Peer AS:  4788
                Age: 30w1d 20:46:03     Metric2: 2400 
                Task: BGP_4788.10.233.32.17+52531
                AS path: I (Originator) Cluster list:  10.233.32.16
                AS path:  Originator ID: 10.233.32.17
                Communities: target:10.233.38.59:6
                Import Accepted
                Localpref: 100
                Router ID: 10.233.32.17
                Secondary Tables: TM_IPTV_HSBB.mvpn.0
                Indirect next hops: 1
                        Protocol next hop: 10.233.32.17 Metric: 2400
                        Indirect next hop: 2 no-forward
                        Indirect path forwarding next hops: 4
                                Next hop type: Router
                                Next hop: 10.55.36.148 via ge-0/0/0.0 weight 0x1
                                Next hop: 10.55.36.150 via ge-1/0/0.0 weight 0x1
                                Next hop: 10.55.36.150 via ge-1/0/0.0 weight 0x4001
                                Next hop: 10.55.36.148 via ge-0/0/0.0 weight 0x4001
                        10.233.32.17/32 Originating RIB: inet.3  <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
                          Metric: 2400                    Node path count: 1
                          Forwarding nexthops: 4
                                Nexthop: 10.55.36.148 via ge-0/0/0.0
                                Nexthop: 10.55.36.150 via ge-1/0/0.0
                                Nexthop: 10.55.36.150 via ge-1/0/0.0
                                Nexthop: 10.55.36.148 via ge-0/0/0.0
Case 2: BGP protocol next-hop exists in table inet.0 only.
 
<----Route resolution is kept by default.
> show configuration routing-options resolution | display inheritance no-comments 

{MASTER}
<----As a BGP protocol next-hop, 202.165.59.11 exists in table inet.0 only.
> show route 202.165.59.11 exact 

inet.0: 58 destinations, 58 routes (57 active, 0 holddown, 1 hidden)
+ = Active Route, - = Last Active, * = Both

202.165.59.11/32   *[OSPF/10] 00:35:32, metric 20
                    > to 192.168.2.1 via xe-0/0/0.0

{MASTER}
<----BGP uses table inet.3 to resolve protocol next-hop 10.233.32.17 for NG-MVPN prefix.
> show route table bgp.mvpn-inet6.0 match-prefix 6:7473:1501:7473:128:2001:1:1::1:128:ff08::1/432 extensive 

bgp.mvpn-inet6.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
6:7473:1501:7473:128:2001:1:1::1:128:ff08::1/432 (1 entry, 0 announced)
        *BGP    Preference: 170/-101
                Next hop type: Indirect
                Address: 0xce96ba8
                Next-hop reference count: 2
                Source: 202.165.59.11
                Protocol next hop: 202.165.59.11
                Indirect next hop: 2 no-forward
                State: 
                Local AS:  7473 Peer AS:  7473
                Age: 34:49      Metric2: 20 
                Task: BGP_7473.202.165.59.11+55670
                AS path: I (Originator)
                Cluster list:  202.165.59.11
                Originator ID: 202.164.59.11
                Communities: target:202.164.59.21:526
                Import Accepted
                Localpref: 100
                Router ID: 202.164.59.11
                Secondary Tables: vrf-1501.mvpn-inet6.0
                Indirect next hops: 1
                        Protocol next hop: 202.165.59.11 Metric: 20
                        Indirect next hop: 2 no-forward
                        Indirect path forwarding next hops: 1
                                Next hop type: Router
                                Next hop: 192.168.2.1 via xe-0/0/0.0
                        202.165.59.11/32 Originating RIB: inet.0  <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
                          Metric: 20                      Node path count: 1
                          Forwarding nexthops: 1
                                Nexthop: 192.168.2.1 via xe-0/0/0.0

{MASTER}

In conclusion

Regarding NG-MVPN (v4 and v6), BGP will try to resolve its protocol next-hop in the table inet.3 first. If this fails, it will resolve in the table inet.0.

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