Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Community Member

BGP migration interfering with previously seamless Backup ISDN failover

We ran and still run Eigrp. We kept a simple floating static route (AD of 120) to route IP out the Bri interface should the Primary Serial Int fail. Since the introduction of BGP (MCI Private INTERNET) our routers are essentially edge routers. When the primary interface fails on one end the Backup INt (120) routes into a "black hole of BGP" on the remote end, until of course BGP (20) can figure out the route is no longer valid. Former 2 second failover is now turning into 1:20 second failover. What direction should I be persuing before impulsively grabbing the duct tape??? Bottom line BGP is not getting the word that our Remote End has failed, while EIGRP always did this instantaneously.

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: BGP migration interfering with previously seamless Backup IS

If the interface to the SP goes down, bgp fast-external-fallover should take the BGP session down automatically. This feature is on by default.

If the interface doesn't go down then the best way to quickly detect that the peer is not responding is to lower the BGP timers (ie: timers bgp 3 9).

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
3 REPLIES
Cisco Employee

Re: BGP migration interfering with previously seamless Backup IS

If the interface to the SP goes down, bgp fast-external-fallover should take the BGP session down automatically. This feature is on by default.

If the interface doesn't go down then the best way to quickly detect that the peer is not responding is to lower the BGP timers (ie: timers bgp 3 9).

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

Re: BGP migration interfering with previously seamless Backup IS

If the interface to the SP goes down, bgp fast-external-fallover should take the BGP session down automatically. --that much is true on either or end. It is the remote end or the UNFAILED BGP side that the message is not propogating. For instance the UK fails. BGP Notifies UK PE neigbor is down. On the NY side the news of the UK side's PE neighbor is never propogated to either the NY PE or CE. Therefore the UK sends data over the backup link immediately to NY and NY replies out the now invalid BgP interface till it realizes there is no route. For well over a minute the NY data sends the UK replies into the oblivion of a failed BGP route till convergence can occur.

Community Member

Re: BGP migration interfering with previously seamless Backup IS

Final on this was I had to make sure that not only did we adjust these timers with our neighbors locally but the Providers PE to PE adjusted their neigboring timers between themselves as well..took about 3 weeks to grasp...Thanks!!

213
Views
0
Helpful
3
Replies
CreatePlease to create content