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.

New Member

Redundancy on serial links

I am currently working on a remote office with two leased line connections terminated on two different routers toward our headquarters.

Router_A, with 512k leased line connection attached to it is directly connected to our head office. Another router named Router_B, with 256k leased line connection attached is connected to another satellite office and this satellite office has 512k leased line connection towards our headquarters.

My questions are:

1. How do I configure/enable network redundancy/resiliency for my network such that if the leased line attached to Router_A goes down, all data will be routed automatically to Router_B via our satellite office and then headquarters ? And on the other hand, if the leased line connection attached to Router_B goes down, data will also be automatically routed to Router_A ? In this case, I will have a minimum downtime and more productivity for my company.

By the way, I have a static route from Router_A pointing directly to the serial interface of my headquarter's router and the same with Router_B.

2. Would it be possible if I have a Cisco switch that if this switch fails ... it will automatically switch to another switch ?

Hope you can help me with my queries.



New Member

Re: Redundancy on serial links

try getting rid of the static routes and enabling any dynamic routing protocol, I would pick ospf or eigrp. Either one of these will learn both routes to headquarters and take the shortest one, upon that route failing, the next route will pick up. Since the links are point to point, cutover should be almost instant.

New Member

Re: Redundancy on serial links

So static route could not address the problem that I am trying to solve ?

If I upgrade from static to dynamic routing ... what are the problems that we surely would encounter ?

Could you point me to a good documentation on how to implement ospf and eigrp.



Re: Redundancy on serial links

If this is the only two sites you have, just setting the static routes up pointing to the interfaces, as it sounds like you have, should work with a minimum of downtime, as long as the interface actually goes down when the link fails (which isn't always the case). Running a dynamic protocol would give you layer 3 hello's, which would discover a link failure even if the interface stays up. So that's at least one reason to consider dynamic routing over these interfaces. Network manageability, if the network is large, is another one--large numbers of manually configured static routes are hard to manage.

The config guides on cisco online:

Should be a good start on basic configuration for these.

For your second question, about the switches, this is what switches are supposed to do, using the spanning tree protocol.


CreatePlease login to create content