glbp+bgp, incoming traffic question

Unanswered Question
May 29th, 2008
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Hello everyone.

We have a topology like this:







R1, R2 are our edge routers (4506)

X1, X2 are let's call it ISP routers

I is router to go into outside of the network

(some extra words about the connections:

The R1 is connected to the X1 and R2

The R2 is connected to the X2 and R1

The X1 is connected to the R1 and I

The X2 is connected to the R2 and I

The I is connected to the X1/X2)

For now, we are not using R2, all the traffic is going thru the R1, it is working fine.

We are using BGP to exchange routes with our ISP (between routers R1 and X1), R2 and X2 are nowadays backup routers.

In lab I tested the HSRP between R1 and R2, and it was working fine. But then, question about the load balancing came.

Well, the GLBP can be done between R1 and R2 and load balancing for the outgoing traffic will be achieved.

But what about the incoming traffic? In case of no changes at the X1 and X2 level, all the traffic will come back to the our internal network (behind R1/R2) using only the link R1-X1 (because of BGP, more weight had this link).

I'm pretty sure that we need to do something on the ISP X1/X2 routers, let's say it is possible, but not huge steps like to resign from BGP. ;)

All ideas are warmly welcome, thank you.

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ebreniz Wed, 06/04/2008 - 06:28
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Hot Standby Router Protocol (HSRP) is used to build redundancy into IP networks. HSRP

ensures that network downtime due to failure of devices is minimal and that the process of

the backup device taking over the forwarding function is transparent to the end user.

However, HSRP cannot influence the path taken by the traffic entering the Autonomous

System (AS). Border Gateway Protocol (BGP) can be used to influence the path taken by the

incoming traffic, but it cannot provide first-hop failure redundancy for hosts on the

network. HSRP and BGP together can influence the path for both incoming and outgoing

traffic if connectivity to one Internet Service Provider (ISP) fails. Then the backup path

to the other ISP used.


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