From: Ken.Farrington@barclayscapital.com
Date: Tue Sep 30 2003 - 09:21:15 GMT-3
Hello all,
I have a question re the setup below.
I have two routers peering eBGP with an external AS 350 and iBGP between the
routers which (just for info) are separate locations.
Now if I receive a route (say 168.1.0.0) that has a metric inbound on both
routers (router76 route for this network has metric of 33 ,and Router12 has
metric for this route of 42) it looks as if the router that has the lowest
metric from the route, does not accept the iBGP route from the other router
with the higher metric, but the router with the higher metric accepts the
iBGP route from the router with the lower metric.
If I receive a route where the metric is not set and all attributes are the
same, it send each other the iBGP route (like 168.41.0.0) and uses it's
local exit point via eBGP to that network.
Please can someone confirm that this is normal operation for iBGP.
Many thx indeed,
Ken
\ 168.1.0.0 168.224.0.0 168.41.0.0 /
\ External /
\ AS 350 /
\__________________________________/
|192.168.42.253 |192.168.41.254
| |
|eBGP |eBGP
| |
| |
| AS 300 |
+--------+ +--------+
|Router76|---------------------|Router12|
+--------+ iBGP +--------+
192.168.42.253 192.168.41.253
on Router76
router bgp 300
neighbor 150.5.36.129 remote-as 300
neighbor 192.168.42.254 remote-as 350
Router76>sh ip int brief
Interface IP-Address OK? Method Status
Protocol
Ethernet0 unassigned YES unset administratively down down
Ethernet1 192.168.42.253 YES NVRAM up up
Loopback0 150.5.32.65 YES NVRAM up up
Network Next Hop Metric LocPrf Weight Path
----------------------------------------------------------------------------
---------------------------
*> 168.1.0.0 192.168.42.254 33 0 350 i This
entry only appears once
----------------------------------------------------------------------------
---------------------------
*>i168.224.0.0 192.168.41.254 31 100 0 350 i
* 192.168.42.254 42 0 350 i
----------------------------------------------------------------------------
---------------------------
* i168.41.0.0 192.168.41.254 100 0 350 i This
entry appears on both
*> 192.168.42.254 0 350 i This
entry appears on both
----------------------------------------------------------------------------
---------------------------
On Router12
!
router bgp 300
neighbor 150.5.32.65 remote-as 300
neighbor 192.254.41.254 remote-as 350
!
Router12>sh ip int brief
Interface IP-Address OK? Method Status
Protocol
Ethernet0 unassigned YES unset administratively down down
Ethernet1 192.168.41.253 YES NVRAM up up
Loopback0 150.5.36.129 YES NVRAM up up
Network Next Hop Metric LocPrf Weight Path
* 168.1.0.0 192.168.41.254 42 0 350 i
*>i 192.168.42.254 33 100 0 350 i
----------------------------------------------------------------------------
---------------------------
*> 168.224.0.0 192.168.41.254 31 0 350 i This
entry only appears once
----------------------------------------------------------------------------
---------------------------
*> 168.41.0.0 192.168.41.254 0 350 i This
entry appears on both
* i 192.168.42.254 100 0 350 i This
entry appears on both
----------------------------------------------------------------------------
---------------------------
________________________________________________________________
Ken Farrington
Global Networks, Barclays Capital, 5 The North Colonnade, Canary
Wharf, London, E14 4BB
* Tel : 020 7773 3550
* Mob : 07768-866655
* ken.farrington@barcap.com
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