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In the network topology shown below, two spokes are connected to a hub using iBGP:
Spoke-1 is advertising 20.20.20.1/24 to the HUB:
# get router info bgp neighbors 10.10.1.1 advertised-routes
VRF 0 BGP table version is 6, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight RouteTag Path
*>i20.20.20.0/24 10.10.1.3 100 32768 0 i <-/->
Total number of prefixes 1
On the hub, the route is received from Spoke-1 and then advertised to Spoke-2:
HUB # get router info bgp neighbors 10.10.1.3 received-routes
VRF 0 BGP table version is 16, local router ID is 10.212.134.201
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight RouteTag Path
*>i20.20.20.0/24 10.10.1.3 100 0 0 i <-/->
Total number of prefixes 1
HUB # get router info bgp neighbors 10.10.1.2 advertised-routes
VRF 0 BGP table version is 16, local router ID is 10.212.134.201
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight RouteTag Path
*>i20.20.20.0/24 10.10.1.3 100 0 0 i <-/->
Total number of prefixes 1
On Spoke-2, the route is received from the HUB but is not being installed in the BGP Table:
SPK_2# get router info bgp neighbors 10.10.1.1 received-routes
VRF 0 BGP table version is 5, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight RouteTag Path
*>i1.1.1.1/32 10.10.1.1 100 0 0 i <0/0>
*>i10.100.0.0/18 10.10.1.1 100 0 0 i <0/0>
*>i20.20.20.0/24 10.10.1.3 100 0 0 i <0/0>
Total number of prefixes 3
The 20.20.20.1/24 network is not present in the BGP table:
# get router info bgp network
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
VRF 0 BGP table version is 5, local router ID is 192.168.1.1
Network Next Hop Metric LocPrf Weight RouteTag Path
*>i1.1.1.1/32 10.10.1.1 0 100 0 0 i <0/1>
*>i10.100.0.0/18 10.10.1.1 0 100 0 0 i <0/1>
*> 10.176.0.0/18 0.0.0.0 100 32768 0 i <0/1>
Total number of prefixes 3
Solution:
Enable BGP debug processes on Spoke-2:
diagnose ip router bgp all enable
diagnose ip router bgp level info
diagnose debug enable
To disable BGP debug processes:
diagnose ip router bgp all disable
diagnose ip router bgp level none
diagnose debug reset
Debug output:
[root] BGP: [RIB] Scanning BGP Network Routes for VRF 0...
[root] BGP: 10.10.1.1-Outgoing [DECODE] Msg-Hdr: type 2, length 53
[root] BGP: 10.10.1.1-Outgoing [DECODE] Update: Starting UPDATE decoding... Bytes To Read (34), msg_size (34)
[root] BGP: 10.10.1.1-Outgoing [DECODE] Update: NLRI Len(9)
[root] BGP: 10.10.1.1-Outgoing [FSM] State: Established Event: 27
[root] BGP: 10.10.1.1-Outgoing [RIB] Update: Received Prefix 1.1.1.1/32 path_id 0
[root] BGP: [DAMP] bgp_rfd_rt_update(): Route State: NONE, ret=0
[root] BGP: 10.10.1.1-Outgoing [RIB] Update: ...duplicate route ignored
[root] BGP: 10.10.1.1-Outgoing [RIB] Update: Received Prefix 10.100.0.0/18 path_id 0
[root] BGP: [DAMP] bgp_rfd_rt_update(): Route State: NONE, ret=0
[root] BGP: 10.10.1.1-Outgoing [RIB] Update: ...duplicate route ignored
[root] BGP: 10.10.1.1-Outgoing [DECODE] Msg-Hdr: type 2, length 62
[root] BGP: 10.10.1.1-Outgoing [DECODE] Update: Starting UPDATE decoding... Bytes To Read (43), msg_size (43)
[root] BGP: 10.10.1.1-Outgoing [DECODE] Update: NLRI Len(4)
[root] BGP: 10.10.1.1-Outgoing [FSM] State: Established Event: 27
[root] BGP: 10.10.1.1-Outgoing [RIB] Update: Prefix 20.20.20.0/24 path_id 0 denied due to originator is us
[root] BGP: bgp_ipc_server_accept:670 create ipc_handler=0x7fb004efb0c0 for sock=29
This issue occurs due to Spoke-1 and Spoke-2 being configured with the same router ID. Manually changing the router ID on either spoke resolves the issue, allowing the route to be installed successfully.
To change Router-ID:
config router bgp
set router-id x.x.x.x <----- Replace x.x.x.x with the IP address that will be used as the router ID.
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