Yeah, it started flapping not long after I posted the first message.
So, I stopped advertising the loop0 interface, and created a totally
new Loop2 interface assigning them IPs of 7.7.7.7/32 and 9.9.9.9/32
for each respective router.
Unfortunately, I'm still getting the same issue, and there's no
flapping this time around. Here's R9's config:
R9(config-router)#do sh ip bgp
BGP table version is 4, local router ID is 50.51.0.9
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 7.7.7.7/32 50.51.0.7 0 0 9 i
*> 9.9.9.9/32 0.0.0.0 0 32768 i
R9(config-router)#do sh run | s bgp
router bgp 7
no synchronization
bgp log-neighbor-changes
network 9.9.9.9 mask 255.255.255.255
neighbor 50.51.0.7 remote-as 9
neighbor 50.51.0.7 ttl-security hops 2
neighbor 50.51.0.7 update-source Loopback0
no auto-summary
R9(config-router)#do sh ip bgp
BGP table version is 4, local router ID is 50.51.0.9
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 7.7.7.7/32 50.51.0.7 0 0 9 i
*> 9.9.9.9/32 0.0.0.0 0 32768 i
R9(config-router)#do sh ip bgp 7.7.7.7/32
BGP routing table entry for 7.7.7.7/32, version 0
Paths: (1 available, no best path)
Not advertised to any peer
9
50.51.0.7 (inaccessible) from 50.51.0.7 (50.51.0.7)
Origin IGP, metric 0, localpref 100, valid, external
R7, which is set up with ebgp-multihop, sees both routes with best paths.
I finally was able to get it show up properly if I enabled the
'neighbor 50.51.0.7 disable-connected-check' option.
R9(config-router)#do sh ip bgp 7.7.7.7/32
BGP routing table entry for 7.7.7.7/32, version 3
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
Not advertised to any peer
9
50.51.0.7 (metric 2) from 50.51.0.7 (50.51.0.7)
Origin IGP, metric 0, localpref 100, valid, external, best
But I couldn't figure out from the description of this option if it
broke the ttl-security check. Thoughts?
On Thu, Jul 9, 2009 at 8:12 PM, Bryan Bartik<[email protected]> wrote:
> Try "debug ip routing". Are you getting recursion errors? It looks like you
> are advertising the loopbacks in BGP which will cause the peers to learn the
> loopback via the loopback. This will cause recursion and removal of the
> route from the BGP table and route table. Then the OSPF route is chosen, BGP
> comes up and the whole process starts agaon.
>
> Don't advertise the loopback in BGP unless required or alter the
> administrative distances so OSPF is preferred over BGP.
>
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