12-12-2007 05:54 PM - edited 03-03-2019 07:54 PM
Can we find a way to enhance BGP stability when we are running on reduced IMA bandwidth.
Our router has 3xT1 IMA, when all 3 T1s are running properly, we have no problems. When a Layer 1 issue occurs on one of the T1s (reduced bandwidth) then the router becomes highly unstable (BGP timeouts/flapping). BGP flaps continuously when we lose a T1, and then the service is unavailable.
Is there a way to create a policy map that will give BGP priority, so we will not experience an "outage" during a layer 1 issue? In other words, BGP will get a level of priority to insure it does not FLAP continuously.
12-12-2007 09:47 PM
I also thought policy-map could be of help here. But one thing to note, best practice is to create a bgp neighbor with loopback address & not physical interface address. If your neighbor is configured on physical interface address & that interface goes down, then you'll loose connection. But if you are already using loopback for neighborship, the here is the policy-map:
BGP runs by establising tcp connection with neighbor over port 179. So you may cretae a policy map & reserve BW for connections with tcp port 179.
access-list 101 permit tcp any any eq 179
clas-map neighbors
match access-list 101
policy-map bgp
class neighbors
bandwidth 100
apply this policy-map to either the physical links or multilink connecting to the neighbor devices.
hope that clarifies.
pls rate all helpful posts.
12-12-2007 10:08 PM
As BVS said, it is always advisable to use the loopback interfaces with BGP
So in case you use loopbacks just prioritise all the traffic between the 2 loopbacks using an access-list which will prioritise all the BGP traffic
access-list BGP permit ip host Loop1 hostloop2
access-list BGP permit ip host Loop2 host loop1
clas-map match-all BGP
match access-list name BGP
policy-map bgp
class BGP
bandwidth 100
Apply this policy on the interface on both ends of the routers
HTH
Narayan
12-12-2007 10:42 PM
HI,
In addition to BVS and Narayan:
Loopback IP Address can be used in BGP for Tunnel Source and Destination. That should be highly enough.
>>If you have enough Bandwidth there is no need for reserving BW to Port 179 - the BGP TCP connection port.
Since you have overloaded Link pls go-ahead with their advices.
DO RATE ALL HELPFUL POSTS
Best Regards,
Guru Prasad R
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