BGP Default Route Question

[ty.masse]

I'm multihoming to two different ISPs. One connection is a T1 the other is an ethernet link. On the ehternet link in my bgp config I have the ebgp multihop command.

What's hapenning is that all outbound internet traffic goes out on the T1 side, and all inbound comes in on the Ethernet side. I want both outbound and inbound to use the Ethernet side, unless there is an outage. In that case In and Out traffic would use the T1 side. I would rather not staticaly put a default route in the router.

When I do a show ip route, statement below shows up as a default gateway that bgp added. How do I change that to the other interface/network?

Thanks,

B* 0.0.0.0/0 [20/0] via 129.x.x.x, 06:15:24

[spremkumar]

Hi

if i would hve been in ur place i would better use weight option here to push my out traffic via Ethernet.

i will configure more weight than the T1 which can make u r outgoin traffic to take the Ethernet path.

For incoming do confirm whether if u have already configured as-path prepends thru T1 so as to allow ur incoming traffic to flow via T1 link if u r Ethernet link fails.

BTW i m curious to know how ur forming bgp neighborship here is it with ur loopback or with ur T1,Ethernet ip ??

regds

[ty.masse]

How is the weight configured? and What is the optimal number to give it?

As for the second part of your message: I don't have as-path prepend thru T1 because I'm being advertised by both ISPs. So there is a path back to me from the internet.

I'm peering from the T1 and Ethernet iterfaces. I'm not using the loopback interface.

Thanks for helping me out.

[vcjones]

First, make sure you are receiving a default route from your Ethernet BGP peer. Talk to your ISP to adjust their configuration to send it if required.

Once you have an incoming default route to work with, you can set the local preference on that route to make it the preferred route. That way, it will go away when the route fails.

Hint: you may want to consider using "indicator routes" rather than blindly accepting a default route from each ISP. Typically, an ISP's default route advertisement is generated locally and has no relationship to how well that specific router is actually connected to the rest of the Internet. By making your default route conditional on the ability of your ISP's router to "see" upstream routers, you can protect yourself against ISP problems without having to take full routing tables.

Good luck and have fun!

Vincent C Jones

www.networkingunlimited.com