Routing

[sathish.ippani]

Hi All,

I would like to know route propagation is possiable as mentioned below.

FYI, please find the attached Network diagram.

Scenario 1:-

From Site 1 it will use Sprint to reach all sites.

Currently, if Sprint link(shown in red line) down at site1 it will use Level3 link (Shown in Green) to Site2 and for Site3, 4 and 5 it will go to data center and use Sprint.

But we want, If Sprint link(shown in red line)  at site1 goes down, it should use Level3 link to Site2 and for site3, 4 and 5 it should use sprint from Site2.

i,e Ex: from Site 1 to site 3

Site1 (Level3)-->(Level3) site2-->Sprint link Site2 to Site3.

[Jon Marshall]

It's not possible to be precise because you haven't said how routing information is propagated so this is a general answer.

Yes it should be possible. You just need to influence the routing within your setup so that site 1 prefers the routes for sites 3, 4 and 5 received from site 2 rather than the DC.

If the link from site 1 to site 2 goes down though I assume you would want site 1 to use the DC to get to sites 3, 4 and 5 ?

Can't really say anymore than that because you haven't given enough information.

Note also that I say it should be possible but depending on your existing routing setup it may not necessarily be simple.

Jon

[sathish.ippani]

Hi John,

Here Level3 use BGP and Sprint Use Eigrp routing protocol.Plz let me know if you need any more info.

If possiable please share any doc that explains my requirement.

[Jon Marshall · Accepted solution]

There isn't really any document for this and no quick answer.

Your DC is currently advertising site's 3,4 and 5 subnets to site 1. You probably still need this as a backup (although you didn't answer my question in the last post) but what you need to do is -

1) make sure that site 2 is advertising site's 3,4 and 5 to site 1 as well

2) make site 2's advertisements the preferred routes rather than the routes received from the DC.

I'm assuming that if you want site 1 to go via site 2 to get to sites 3,4,5 then you also want return traffic from those sites to go back via site 2 and not the DC. If so -

3) you are also going to have advertise site 1's subnets from site 2 into the Sprint cloud so that sites 3,4 and 5 know where to send return traffic.

4) following on from 3) you will need to make sure that if site 1's Sprint link is up then sites 3, 4 and 5 go direct to site 1 and not via site 2.

This could get quite complex as you can hopefully see. It will involve BGP configuration and EIGRP configuration and the EIGRP configuration could get quite tricky.

I would suggest firstly looking at all the routing tables to see exactly what is where and you certainly need a full understanding of how everything works now before you can begin to make any changes.

Jon

[sathish.ippani]

Thanks John. I will do testing on Gns3 and let u know.