Help Please Active/Standby ISP Link

[fatalXerror]

Hi Guys,

Good Day!

Need help, I have 2 routers which I will be configuring as my edge routers and this routers will be having iBGP in each others and eBGP for ISP links however, I only have 1 ISP with 1 router only meaning my 2 routers will be connecting to the sole ISP router.

I would like to seek help how can I do it so that there will be primary and secondary link towards the ISP router?

Thanks

[nagasheshu2010 · Accepted solution]

Hi,

Hope you are doing well.

I would like to understand your question little more.

"I only have 1 ISP with 1 router only meaning my 2 routers will be connecting to the sole ISP router." - Means, the EDGE(CPE routers) connects to same ISP and same router?

Sheshu.

[fatalXerror]

Hi nagasheshu2010,

Good Day!

You are correct, I have 2 CPE routers which I wanted to connect to only 1 ISP (1 router).

Can you help me please.

Thanks

[nagasheshu2010]

Well, you can do the following.

Lets suppose router 1 is primary and router 2 is secondary.

To control outgoing traffic, use "as-path prepend in" feature in router 2.

To control incoming traffic, use MED feature. Apply low MED in router 1 and high in router 2 or you can ask ISP to apply high Local preference for router 1 BGP neighbor and low LP for router 2 BGP neighbor.

Hope this helps.

let me know if you are looking for config template.

Sheshu.

[fatalXerror]

Hi nagasheshu2010,

Good Day!

May I ask why only Router 2 will be configured with "as-path prepend in"?

Thanks

[nagasheshu2010]

When two or more routes exist to reach a particular prefix the default in BGP is to prefer the route with the shortest AS Path length.

Lets assume we are receiving "x route" on router 1 and router 2 with same AS path then the decision goes to the next BGP attributes.

IF we apply, "as path prepend in" in router 2 and change the as path of "x route" to something higher in router 2 than the router 1, then it prefers router 1 route.

Hope this explains.

Sheshu.