09-23-2010 11:44 AM - edited 03-04-2019 09:52 AM
RELEVANT CONFIG:
router ospf XXXXX
log-adjacency-changes
redistribute connected subnets
redistribute static subnets
passive-interface default
no passive-interface GigabitEthernet0/0.54
network XX.XX.XX.XX 0.0.0.0 area 0
default-information originate
!
router ospf 65501
log-adjacency-changes
redistribute connected subnets
redistribute static subnets
redistribute bgp XXXXX subnets
passive-interface default
no passive-interface GigabitEthernet0/0.50
network XX.XX.XX.XX 0.0.0.0 area 0
default-information originate
!
router bgp XXXXX
no synchronization
bgp log-neighbor-changes
network XX.XX.XX.XX mask 255.255.255.255
network XX.XX.XX.XX
network XX.XX.XX.XX mask 255.255.224.0
network XX.XX.XX.XX mask 255.255.255.0
aggregate-address XX.XX.XX.XX 255.255.224.0 summary-only
neighbor XX.XX.XX.XX remote-as XXXX
neighbor XX.XX.XX.XX description DIA B-Peer (Receive from this node via loopback 10)
neighbor XX.XX.XX.XX password 7 X
neighbor XX.XX.XX.XX ebgp-multihop 5
neighbor XX.XX.XX.XX update-source Loopback10
neighbor XX.XX.XX.XX soft-reconfiguration inbound
neighbor XX.XX.XX.XX filter-list 1 in
neighbor XX.XX.XX.XX remote-as XXXX
neighbor XX.XX.XX.XX description DIA A-Peer (Announce to this node)
neighbor XX.XX.XX.XX password 7 X
neighbor XX.XX.XX.XX filter-list 2 in
maximum-paths 6
no auto-summary
When pinging to one of the nodes in this lab environment, if I ping simply from the DIA edge router, pings go through without any pauses or issues. If I ping from int gi0/0.54- then it will start, then go out 3 seconds, start, go out 14 seconds, start, go out 3 seconds- then go for a while. There is obviously something goofy going on in the routing table, but I cant seem to find out what. I've done bgp and ospf debugs with no success. The routing table seems to be solid and not changing. Recommendations?
09-23-2010 01:34 PM
Hello Greg,
You have two OSPF processes and BGP process.
>> f I ping simply from the DIA edge router, pings go through without any pauses or issues. If I ping from int gi0/0.54- then it will start, then go out 3 seconds, start, go out 14 seconds, start, go out 3 seconds-
Timing may be meaningful, I would say that it may be related to BGP.
you can use debug ip routing combined with an ACL to monitor some IP prefix like the ping destination.
How do you reach the BGP next-hop?
This is a key point: the BGP next-hop may be at the beginning considered valid and later dismissed if on BGP you receive a better route ( more specific) with that BGP next-hop.
You can use a /32 static route to fix this if this is the trouble.
IT is a consistency check the BGP next-hop cannot be validated by a BGP route received on that same eBGP session.
After the BGP next-hop is considered not valid the BGP route is damped and the process repeats over time: the BGP next-hop is again validated and the route accepted but then at next BGP next hop validation check the test fails.
Hope to help
Giuseppe
09-23-2010 02:03 PM
I have already adjusted the BGP timers, with no change in the result. The bgp nexthop is reached via static route for the host. I figured that the next-hop might be dropping out of the routing table. The last thing I did was actually enter that static route. It produced no change.
01-20-2011 07:05 AM
I am having almost the exact same thing happening. I have a remote site connected to our corporate office via At&t MPLS. At
the remote site, I have a 3750 for layer 3. Coming off of the 3750 I have a 2801 router connected to the At&t managed WAN router.
I am running OSPF on the 3750 and running OSPF and iBGP on the 2801. From the 3750, I can ping multiple networks at the corporate office all day. As soon as I try to access any application (can be on different networks at corporate office) the network drops from route table on the 2801 and 3750.
When the appliction times out, the route is immediately put back into the routing table on both devices and pinging resumes. I know a better route isn't being found, I have only one egress point at this site currently.
01-20-2011 07:20 AM
Hello Tbulliard,
so in the remote office you have:
C3750 ---- C2801 ----- AT&T device ----- MPLS cloud ----- HQ --- application servers
in your case it looks like that at some point in the path the application traffic fills the pipe and BGP messages are dropped causing the routing failure
can you check in C2801 using
show ip bgp sum
the uptime of the BGP session?
is this a L3 VPN or a different service?
if the uptime is not great this might be part of the problem
also
show log
should show BGP related messages
Hope to help
Giuseppe
01-20-2011 07:15 AM
If there is no recurring pattern to the drops i suggest you check the interface on the local and intermediate devices between the source and the destination
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