From: Gregory Gombas (ggombas@gmail.com)
Date: Wed Sep 05 2007 - 12:14:20 ART
|--R2--|
R1---| |
|--R3--|
R1 is running RIP only.
R2 and R3 are running RIP and are eBGP peers.
R2 and R3 are mutually redistributing between RIP and BGP.
Most of the routes from R1 are showing up properly as RIP routes
on R2 and R3 with R1 as the next hop. However one route is showing as
a BGP route on R3 with R2 as the next hop and R2 is showing the same
route as a RIP route with R3 as the next hop.
I'm pretty sure this has something to do with the timing of what
router learns the route first and redistributes into BGP, but my
question is why isn't this happening to all the routes then?
Here is a sample BGP table entry for a route that is working fine:
R2:
show ip bgp 1.1.1.0
BGP routing table entry for 1.1.1.0/24, version 200
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Advertised to update-groups:
AS3, (received & used)
R3 Loopback Address (metric 1) from R3 Loopback Address
Origin incomplete, metric 10, localpref 100, valid, external
Local
R1's IP from 0.0.0.0 (R2 Loop address)
Origin incomplete, metric 10, localpref 100, weight 32768,
valid, sourced, best
R3:
show ip bgp 1.1.1.0
BGP routing table entry for 1.1.1.0/24, version 200
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Advertised to update-groups:
AS2, (received & used)
R2 Loopback Address (metric 1) from R2 Loopback Address
Origin incomplete, metric 10, localpref 100, valid, external
Local
R1's IP from 0.0.0.0 (R3 Loop address)
Origin incomplete, metric 10, localpref 100, weight 32768,
valid, sourced, best
As you can see both routers are redistributing the RIP route into BGP
and are preferring their locally originated BGP routes (so they are
not using their peer's BGP route).
In the case of the route that is not working properly:
R2:
show ip bgp 1.1.2.0
BGP routing table entry for 1.1.2.0/24, version 200
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
Local
R3's IP from 0.0.0.0 (R2 Loop address)
Origin incomplete, metric 2, localpref 100, weight 32768, valid,
sourced, best
R3:
show ip bgp 1.1.2.0
BGP routing table entry for 1.1.2.0/24, version 200
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
AS2, (received & used)
R2 Loopback Address (metric 1) from R2 Loopback Address
Origin incomplete, metric 2, localpref 100, valid, external
As you can see R3 is not locally originating the route, it is using
the BGP route from R2.
So is this simply a timing issue here as to who learns the RIP route
first and redistributes into BGP?
If that is the case why aren't all routes experiencing this issue?
This archive was generated by hypermail 2.1.4 : Sat Oct 06 2007 - 12:01:09 ART