Hi a short question to BGP.
AS 65005----------------------------------------------------------------------------AS65024
RT51 RT21
| |
| |
AS 65008---------------------------------------------------------------------------AS65013
RT52 RT12
I created the circle of 4 AS above. If i now add via network comand on router RT12 (AS65013) a network the following debug is shown on router RT12 and router RT21. The text showes me that the update is send as i expected.
*Apr 12 07:15:36.190: BGP(0): (base) 172.12.21.2 send UPDATE (format) 192.168.1.32/28, next 172.12.21.1, metric 0, path Local
*Apr 12 07:15:36.194: BGP: 172.12.21.2 Next hop is our own address 172.12.21.1
The next part confuses me a little bit. Why is router RT21 sending me the update back? I understand why it is blocked because of AS-Path but i don´t understand why it is send back on the same link?!
RT_12(config-router)#P(0): 172.12.21.2 rcv UPDATE w/ attr: nexthop 172.12.21.1, origin i, originator 0.0.0.0, merged path 65024 65013, AS_PATH , community , extended community , SSA attribute
*Apr 12 07:15:36.195: BGPSSA ssacount is 0
*Apr 12 07:15:36.195: BGP(0): 172.12.21.2 rcv UPDATE about 192.168.1.32/28 -- DENIED due to: AS-PATH contains our own AS; NEXTHOP is our own address;
below the complete debug of RT 12 and 21
RT_12(config-router)#network 192.168.1.32 mask 255.255.255.240
RT_12(config-router)#
*Apr 12 07:15:36.189: BGP(0): sourced route for 192.168.1.32/28 created
*Apr 12 07:15:36.189: BGP(0): sourced route for 192.168.1.32/28 path 0x7F3FF8723128 id 0 gw 0.0.0.0 created (weight 32768)
*Apr 12 07:15:36.189: BGP(0): local route 192.168.1.32/28 added gw 0.0.0.0
*Apr 12 07:15:36.189: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 192.168.1.32/28
*Apr 12 07:15:36.190: BGP(0): local route 192.168.1.32/28 modified rib-gw 0.0.0.0 path-gw 0.0.0.0 [0x7F3FF8723128:0]
*Apr 12 07:15:36.190: B
RT_12(config-router)#GP(0): redist event (4) request for 192.168.1.32/28
*Apr 12 07:15:36.190: BGP(0) route 192.168.1.32/28 gw-1 0.0.0.0 src_proto (null) path-limit 1
*Apr 12 07:15:36.190: BGP(0): redistributed local route 192.168.1.32/28 modified rib-gw 0.0.0.0 path-gw 0.0.0.0 [0x7F3FF8723128:0]
*Apr 12 07:15:36.190: BGP(0): (base) 172.12.21.2 send UPDATE (format) 192.168.1.32/28, next 172.12.21.1, metric 0, path Local
*Apr 12 07:15:36.194: BGP: 172.12.21.2 Next hop is our own address 172.12.21.1
*Apr 12 07:15:36.194: BG
RT_12(config-router)#P(0): 172.12.21.2 rcv UPDATE w/ attr: nexthop 172.12.21.1, origin i, originator 0.0.0.0, merged path 65024 65013, AS_PATH , community , extended community , SSA attribute
*Apr 12 07:15:36.195: BGPSSA ssacount is 0
*Apr 12 07:15:36.195: BGP(0): 172.12.21.2 rcv UPDATE about 192.168.1.32/28 -- DENIED due to: AS-PATH contains our own AS; NEXTHOP is our own address;
*Apr 12 07:15:36.195: BGP: 172.15.22.2 Next hop is our own address 172.15.22.1
*Apr 12 07:15:36.195: BGP(0): 172.15.22.2 rcv UPDATE w/ attr: n
RT_12(config-router)#exthop 172.15.22.1, origin i, originator 0.0.0.0, merged path 65008 65013, AS_PATH , community , extended community , SSA attribute
*Apr 12 07:15:36.195: BGPSSA ssacount is 0
*Apr 12 07:15:36.195: BGP(0): 172.15.22.2 rcv UPDATE about 192.168.1.32/28 -- DENIED due to: AS-PATH contains our own AS; NEXTHOP is our own address;
----------------------------------------------------------------------------------------
RT_21#
*Apr 12 07:15:36.127: BGP(0): 172.12.21.1 rcvd UPDATE w/ attr: nexthop 172.12.21.1, origin i, metric 0, merged path 65013, AS_PATH
*Apr 12 07:15:36.127: BGP(0): 172.12.21.1 rcvd 192.168.1.32/28
*Apr 12 07:15:36.127: BGP(0): Revise route installing 1 of 1 routes for 192.168.1.32/28 -> 172.12.21.1(global) to main IP table
*Apr 12 07:15:36.128: BGP(0): 172.12.21.1 NEXT_HOP is on same subnet as the bgp peer and set to 172.12.21.1 for net 192.168.1.32/28, flags 200, sb: AC0C1500, mask: FFFFFFFC
*Apr 12 0
RT_21#7:15:36.128: BGP(0): (base) 172.12.21.1 send UPDATE (format) 192.168.1.32/28, next 172.12.21.1, metric 0, path 65013
*Apr 12 07:15:36.135: BGP(0): 172.25.11.2 rcvd UPDATE w/ attr: nexthop 172.25.11.2, origin i, merged path 65005 65008 65013, AS_PATH
*Apr 12 07:15:36.135: BGP(0): 172.25.11.2 rcvd 192.168.1.32/28
Thx for help
Steffen
