bgp

[manivelengg]

sir,

  we have advertised two networks with two isp's via BGP.Suppose if one isp is down,all the traffic should go to second isp but the same two networks should be accessed if any one is down.

how to configure this in our cisco router?

thanks in advance.

[Giuseppe Larosa]

Hello Manivelegg,

if you have two eBGP sessions with two ISP you use them not only to advertise your public IP subnets but also to receive at least a default route in each session.

Use

sh ip bgp 0.0.0.0

to verify that you are receiving two advertisements one from each ISP.

You should be fine already.

if one session goes down your router will automatically use the other default route to send traffic to the internet.

Hope to help

Giuseppe

[Rick Morris]

To verify that your routes are being announced by both ISP's you will need to log into a looking glass and check.

Do a search for any looking glass and verify.

If the one you choose allows cli:  sh ip bgp

do this for both blocks

If no CLI choose the gui function that provides this.

If the routes are not seen via both ISP/AS then make sure you are announcing the IP's to both via:  sh ip bgp neigh adv

This will verify your announcement to that neighbor.  Do this for both neighbors to verify announcement.