How do I configure a router to a secondary ISP

[gturrubi]

I am looking at configuring a router to a secondary ISP using BGP. The router will be located at a remote office and the traffice will be sent or received over a dedicated cross connect on a DS3. I am not using a Firewall or IDS yet at the remote site but will shortly down the road. The goal is to use both primary and secondary ISP's for traffice using load balancing and redundancy in the event that one link goes down.

 

[Frenchie2069]

BGP is not a trivial thing to set up, but there are a couple of things to consider when planning:

* always use route-maps to filter route updates in and out of your AS - don't allow 192.168.x.x, 10.x.x.x, etc in or out and only allow specific networks out (or you might find yourself a transit network for the internet)
* show ip bgp will quickly show which networks you have learned from each ISP
* use reliable links to the ISP as route flapping can cause your network to be dampened and you won't receive any inbound traffic
* Make sure that your router has enough DRAM and CPU to handle a full table (or filter the incoming advertisements so that you have a smaller table). I would recommend at least a 3600 with 128 Mb DRAM to run BGP at all.

Your ISPs should be able to provide you with some help on the config. Have you got your PI space and AS number yet?

Cheers,
Michael.

 

[StarTAC]

multihoming.. yes..

u need to get your AS#, as well address space that u will announce to the Internet... without this, multihoming would be useless, if not futile..

good luck..

 

[tschouten]

Hail to startac and Frenchie2069

Good info

 

[Frenchie2069]

How about a star then

 

[gturrubi]

Thanks for the Infor, I was plannig on using a Cisco 2611 with Max memory and flash (16mb) for this configuration, any thoughts?

 

[webnetwiz]

If you're going to keep full table, I 'd think the router would die ver very fast. If you're planning on deploying a new router to do this, I'd go with a 3725 as the lowest, just because the 3600 are out of production. The 3725 has a 240MHz CPU and I beleive comes with either 128MB or 256MB RAM. Very beefy, and can do BGP without a problem. Also supports various high speed links such as ATM or DS3.

 

[jamin123]

Sample BGP config runing on 2 ISP in my home lab. Hope this help.

hostname RouterA
int e0
ip address 193.10.2.1 255.255.255.0
no shut
int s0
ip address 200.200.200.65 255.255.255.252
no shut
int s1
ip address 130.150.33 255.255.255.252
no shut
router bgp 300
neighbor 130.1.50.34 remote-as 200
neighbor 200.200.200.65 remote-as 400
network 193.10.2.0



hostname RouterB
int e0
ip address 12.0.0.1 255.255.0.0
no shut
int s0
ip address 130.1.50.34 255.255.255.252
no shut
router 200
neighbor 130.1.50.33 remote-as 300
network 12.0.0.0

hostname RouterC
int e0
ip address 11.0.0.1 255.255.0.0
no shut
int s0
ip address 200.200.200.66 255.255.255.252
no shut
router bgp 400
neighbor 200.200.200.63 remotes-as 300
network 11.0.0.0