Advice on route reflectors

Hi All

I have a topology at hand, 2 RR and 2 clients. Let me call them RR1, RR2 and RRC1 and RRC2 to have the description done.

it is built in a way where RR1 will an IBGP to RR2. From there, it will have 2 clusters where RR1 will have cluster 8.8.8.8 to RRC1 and cluster 9.9.9.9 to RRC2. RR2 will have cluster 8.8.8.8 to RRC1 and also having cluster 9.9.9.9 to RRC 2.

Things are working okay, i can receive the route 20.2.0.0 from both the RRC in my RR1, and i am annoucing this towards RR2 with the cluster and the originator ID, insicating that the route is reflected by the RR correctly. I am rather confused when i checked RR2, that i do not have the route received from RR1. instead i have 2 bgp path towards 20.2.0.0 via RRC1 and RRC2 and i dont seem to have any bgp path towards 20.2.0.0 via RR2. Is this a loop menhanisam, or a router will install a bgp path preferring from an ibgp neighbor rather then a route reflected route ?

Below would be a drawn lab and after which the show output. Appreciate the kind souls out there to help me understand this 

image

 

RRC1#sh ip bgp neighbors 100.1.1.1 advertised-routes 

BGP table version is 4, local router ID is 5.5.5.5

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale, m multipath, b backup-path, x best-external, f RT-Filter

Origin codes: i - IGP, e - EGP, ? - incomplete

 

   Network          Next Hop            Metric LocPrf Weight Path

*> 20.2.0.0/16      0.0.0.0                  0         32768 i

*> 20.3.0.0/16      0.0.0.0                  0         32768 i

*> 20.4.0.0/16      0.0.0.0                  0         32768 i

 

Total number of prefixes 3 

 

RRC2#sh ip bgp neighbors 100.1.1.1 advertised-routes 

BGP table version is 4, local router ID is 6.6.6.6

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 

              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 

              x best-external, a additional-path, c RIB-compressed, 

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

 

     Network          Next Hop            Metric LocPrf Weight Path

 *>  20.2.0.0/16      0.0.0.0                  0         32768 i

 *>  20.3.0.0/16      0.0.0.0                  0         32768 i

 *>  20.4.0.0/16      0.0.0.0                  0         32768 i

 

Total number of prefixes 3 

 

RR1> show route receive-protocol bgp 1.1.1.2 

 

inet.0: 107 destinations, 120 routes (104 active, 0 holddown, 3 hidden)

  Prefix                  Nexthop              MED     Lclpref    AS path

* 20.2.0.0/16             1.1.1.2              0       100        I

* 20.3.0.0/16             1.1.1.2              0       100        I

* 20.4.0.0/16             1.1.1.2              0       100        I

 

iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)

 

inet6.0: 42 destinations, 46 routes (42 active, 0 holddown, 0 hidden)

 

{master}

RR1> show route receive-protocol bgp 2.2.2.2    

 

inet.0: 107 destinations, 120 routes (104 active, 0 holddown, 3 hidden)

  Prefix                  Nexthop              MED     Lclpref    AS path

  20.2.0.0/16             2.2.2.2              0       100        I

  20.3.0.0/16             2.2.2.2              0       100        I

  20.4.0.0/16             2.2.2.2              0       100        I

 

iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)

 

inet6.0: 42 destinations, 46 routes (42 active, 0 holddown, 0 hidden)

 

 

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

 

 

RRC1#sh ip bgp neighbors 100.1.1.2 advertised-routes 

BGP table version is 4, local router ID is 5.5.5.5

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale, m multipath, b backup-path, x best-external, f RT-Filter

Origin codes: i - IGP, e - EGP, ? - incomplete

 

   Network          Next Hop            Metric LocPrf Weight Path

*> 20.2.0.0/16      0.0.0.0                  0         32768 i

*> 20.3.0.0/16      0.0.0.0                  0         32768 i

*> 20.4.0.0/16      0.0.0.0                  0         32768 i

 

Total number of prefixes 3 

 

RRC2#sh ip bgp neighbors 100.1.1.2 advertised-routes 

BGP table version is 4, local router ID is 6.6.6.6

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 

              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 

              x best-external, a additional-path, c RIB-compressed, 

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

 

     Network          Next Hop            Metric LocPrf Weight Path

 *>  20.2.0.0/16      0.0.0.0                  0         32768 i

 *>  20.3.0.0/16      0.0.0.0                  0         32768 i

 *>  20.4.0.0/16      0.0.0.0                  0         32768 i

 

Total number of prefixes 3 

 

RR2> show route receive-protocol bgp 1.1.1.2 

 

inet.0: 91 destinations, 107 routes (89 active, 0 holddown, 2 hidden)

  Prefix                  Nexthop              MED     Lclpref    AS path

* 20.2.0.0/16             1.1.1.2              0       100        I

* 20.3.0.0/16             1.1.1.2              0       100        I

* 20.4.0.0/16             1.1.1.2              0       100        I

 

iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)

 

inet6.0: 19 destinations, 19 routes (19 active, 0 holddown, 0 hidden)

 

RR2> show route receive-protocol bgp 2.2.2.2    

 

inet.0: 91 destinations, 107 routes (89 active, 0 holddown, 2 hidden)

  Prefix                  Nexthop              MED     Lclpref    AS path

  20.2.0.0/16             2.2.2.2              0       100        I

  20.3.0.0/16             2.2.2.2              0       100        I

  20.4.0.0/16             2.2.2.2              0       100        I

 

iso.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)

 

inet6.0: 19 destinations, 19 routes (19 active, 0 holddown, 0 hidden)

 

 

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

 

RR1> show route advertising-protocol bgp 100.1.1.2 20.2.0.0 active-path detail

 

inet.0: 107 destinations, 120 routes (104 active, 0 holddown, 3 hidden)

* 20.2.0.0/16 (2 entries, 1 announced)

 BGP group IBGP-RR type Internal

     Nexthop: 1.1.1.2

     MED: 0

     Localpref: 100

     AS path: [100] I

     Cluster ID: 11.11.11.11

     Originator ID: 5.5.5.5

 

RR2> show route receive-protocol bgp 100.1.1.1 20.2.0.0 

 

inet.0: 91 destinations, 107 routes (89 active, 0 holddown, 2 hidden)

 

RR2>  

 

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

 

 

RR1> show route 20.2.0.0 detail 

 

inet.0: 107 destinations, 120 routes (104 active, 0 holddown, 3 hidden)

20.2.0.0/16 (2 entries, 1 announced)

        *BGP    Preference: 170/-101

                Next hop type: Indirect

                Address: 0x92b9e58

                Next-hop reference count: 9

                Source: 1.1.1.2

                Next hop type: Router, Next hop index: 1100

                Next hop: 1.1.1.2 via ge-2/3/5.0, selected

                Session Id: 0x21b

                Protocol next hop: 1.1.1.2

                Indirect next hop: 95a8000 1048574 INH Session ID: 0x220

                State: <Active Int Ext>

                Local AS:   200 Peer AS:   100

                Age: 13:34      Metric: 0       Metric2: 0 

                Validation State: unverified 

                Task: BGP_100_100.1.1.1.2+46007

                Announcement bits (4): 0-KRT 3-RT 8-BGP_RT_Background 9-Resolve tree 4 

                AS path: I

                AS path: Recorded

                Accepted

                Localpref: 100

                Router ID: 5.5.5.5

         BGP    Preference: 170/-101

                Next hop type: Indirect 

                Address: 0x92ba610

                Next-hop reference count: 3

                Source: 2.2.2.2

                Next hop type: Router, Next hop index: 1611

                Next hop: 100.1.1.35 via ge-1/2/1.0, selected

                Session Id: 0x20d

                Protocol next hop: 2.2.2.2

                Indirect next hop: 95a80ec - INH Session ID: 0x0

                State: <NotBest Int Ext>

                Inactive reason: Not Best in its group - Router ID

                Local AS:   200 Peer AS:   100

                Age: 12:50      Metric: 0       Metric2: 0 

                Validation State: unverified 

                Task: BGP_100_100.2.2.2.2+57459

                AS path: I

                AS path: Recorded

                Accepted

                Localpref: 100

                Router ID: 6.6.6.6

 

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

 

RR2> show route 20.2.0.0 detail 

 

inet.0: 91 destinations, 107 routes (89 active, 0 holddown, 2 hidden)

20.2.0.0/16 (2 entries, 1 announced)

        *BGP    Preference: 170/-101

                Next hop type: Indirect

                Address: 0x92b63b0

                Next-hop reference count: 9

                Source: 1.1.1.2

                Next hop type: Router, Next hop index: 691

                Next hop: 100.1.1.34 via ge-1/2/1.0, selected

                Session Id: 0x37945

                Protocol next hop: 1.1.1.2

                Indirect next hop: 9538000 1048574 INH Session ID: 0x37d23

                State: <Active Int Ext>

                Local AS:   100 Peer AS:   100

                Age: 13:23      Metric: 0       Metric2: 0 

                Validation State: unverified 

                Task: BGP_100.1.1.1.2+14793

                Announcement bits (4): 0-KRT 2-RT 8-BGP_RT_Background 9-Resolve tree 4 

                AS path: I

                AS path: Recorded

                Accepted

                Localpref: 100

                Router ID: 5.5.5.5

         BGP    Preference: 170/-101

                Next hop type: Indirect 

                Address: 0x92b5b60

                Next-hop reference count: 3

                Source: 2.2.2.2

                Next hop type: Router

                Next hop: 2.2.2.2 via ge-1/3/5.0, selected

                Session Id: 0x0

                Protocol next hop: 2.2.2.2

                Indirect next hop: 95380ec - INH Session ID: 0x0

                State: <Int Ext>

                Inactive reason: Router ID

                Local AS:   100 Peer AS:   100

                Age: 12:39      Metric: 0       Metric2: 0 

                Validation State: unverified 

                Task: BGP_100.2.2.2.2+31649

                AS path: I

                AS path: Recorded

                Accepted

                Localpref: 100

                Router ID: 6.6.6.6

Comments

  • I am rather confused when i checked RR2, that i do not have the route received from RR1. instead i have 2 bgp path towards 20.2.0.0 via RRC1 and RRC2 and i dont seem to have any bgp path towards 20.2.0.0 via RR2. Is this a loop menhanisam, or a router will install a bgp path preferring from an ibgp neighbor rather then a route reflected route ?

    Hi,

    probably from what you reported if both route reflector clients are configured with same cluster-id from RR server perspective, once the aggregate is passed towards RR1 from both clients and reflected to RR2 the update is discarded because it contains the same cluster-id.

    Try debug bgp ipv4 unicast updates on inbound direction on RR2 and clear the session on RR2. If you want RR2 receive the same aggregate also from RR1 you should program different cluster ids for the session from RR1 towards its clients or make the relationship between the two RR servers as client relationship and not as non-client relationship.

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