We are using 2 BGP Routers to have Redundancy in a Multihomed BGP Network. Each router has an connection to an different ISP. The Routers are connected each other via fast ethernet and iBGP Peers using HSRP. Now we have the Problem that one router overwrites the routes from the eBGP (ISP) Peer with the Routes from the iBGP Peer although they have an worse metric. The neighbours are still up. If we shutdown the Fast Ethernet Interface than the router keep the route entrys. Does anybody has an idea what could be the reason for this behavior.
Thanks for all responses. In the meantime we recognized new things.
R2 is usually the active HSRP speaker. To reach a unequal loadsharing we configured as-path-prepend on R1 who is usually standby HSRP speaker. This scenario worked till last weekend. But now maybe something in the ISP network happend. Now It is only working if we disconnect the connection between R1 and R2 (the iBGP Peer). So without an iBGP Peer between them each of the router keep the BGP route entrys from the ISP with an distance of 20 in the routing table. As soon as we connect the router again, R2 overwrites the Routing entrys with a distance of 200 from the iBGP Peer. And also after 60 sec. both neighbours went to state idle.
R2#sh ip bgp summ
BGP router identifier 192.168.35.2, local AS number 21026
BGP table version is 127717, main routing table version 127717
121434 network entries and 274606 paths using 21664914 bytes of memory
30810 BGP path attribute entries using 1602120 bytes of memory
28185 BGP AS-PATH entries using 805624 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
Dampening enabled. 0 history paths, 0 dampened paths
121408 received paths for inbound soft reconfiguration
The only thing we changed is to put an second Loopback (lo1) address on the routers. This Loopback address is now used as BGP Router ID. But we thought that this can not be the problem because we use update source loopback0 for the iBGP Peer .
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