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

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

Internet backup link-no bgp

we having 512k interlink ,now we will be going for backup internet link from different service provider .

The backup link should autommatically come up when the primary link goes down and web mail server should be active when the back up link active.

we have 3800 series router and we don't want run bgp.

could any one guide me to go ahead for this.

coluld any one help me to solve the issue.


Re: Internet backup link-no bgp


You can always configure a backup link by adding following commands


backup interface

backup delay 1 1

ip route 50"

but from your explaination of your network what is my concern is that if you are running a web/mail server in your LAN and they had to be available from internet, then how will you define them< will you give 2 IPs to everyone?)

Pls rate helpful posts.



Re: Internet backup link-no bgp


the problem has two components:

1) traffic leaving your site towards the internet

2) traffic arriving from the internet towards your Web mail servers (is it web mail or web and mail?)

For problem 1) there is a rather simple solution: use two static routes. An example IP routing config for a single router would look like this:

interface Serial0/0

description to ISP A

ip address

interface Serial0/1

description to ISP B

ip address

ip route Serial0/0

ip route Serial0/1 250

The second default route will only be used, if the first one is invalid, i.e. if Serial0/0 is down. You need to adjust interface names and IP addresses.

Regarding problem 2) the situation is much more complicated. The first question is: how do clients connect to your Web mail servers? Are they using DNS or are they connecting to a specific IP? Is the IP of the servers registered to you (which I doubt) or to ISP A? In the latter case the problem is, that it is unlikely to convince ISP B to route traffic towards addresses from ISP A to your site AND announce those addresses to the internet.

If you have NAT in place the situation gets even more complicated. So could you please clarify the suggested setup regarding IP addresses and the way clients will find the server. If this is known, the answer will be more easily described.

regards, Martin

Re: Internet backup link-no bgp


regarding problem 2,

our clients connect to our web mail server by using DNS .

Ip of the servers registered in ISP A and we are using static nat for webmail server to connect outside .

i belive we can use secondary ip address for the mail server , what would be the router configuration side (shall we use two static nat for the same web mail server ?)

CreatePlease login to create content