need to connect through two ISPs

Unanswered Question
Jul 27th, 2007

Hi,

I have a little doubt, it'll be appreciated if somebody can help me.

I want to connect my network of /22 pool through two different ISPs. I want one part of my network traffic to flow through 1 gateway and rest through another 1. Also if there is any link failure in any 1 of the link that time whole traffic should go through another link. This transfer should be automatic.

I think its possible in BGP configurations, but i dont hav the exact idea. Kindly help me. sample configuration will be helpfull. Also let me know can we use default routing in this situation.

Regards,

I have this problem too.
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Amit Singh Fri, 07/27/2007 - 01:54

Do you have your own public AS number to run BGP with two different service providers. If yes, then you have to do EBP multihoming with 2 ISP's. If you dont have that then you have to use PBR (policy-based routing) and NAT to work it out.

I would first look at the kind of traffic, users, applications that I have to go the outisde world. Once the traffic is determined I would see the traffic distribution of the users over the two links. I would use my application, mail traffic to go thorough one link and internet and other traffic to use another link.I will make both the links as back up of each other.In case of one of the link goes my all the traffic will use the other link. I would suggest to implement proper QOS and rate limiting to drop the unwanted traffic.

NAT:

http://www.cisco.com/warp/public/556/12.html

Policy Based Routing:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/qos_c/qcpart1/qcpolicy.htm

www.cisco.com/warp/public/732/Tech/plicy_wp.htm

QOS:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hqos_c/qchintro.htm

HTH,Please rate if it does.

-amit singh

hai_manish Fri, 07/27/2007 - 02:08

Y i hav my own AS number. i know i'll hav to do EBGP multihoming. can anybody send me any sample configuration of that.

Also my need is very simple, no complex traffic distribution. all kinds of traffic from half of the network should through one gateway and half from another1. how to make both the links backup of each other. give me any sample.

Regards,

rajatsetia Fri, 07/27/2007 - 03:52

hi

very basic, use prefix length concept...

advertise \22 from both the links in addition to subnets with bigger prefix length of \24 from respective links.

when both links are UP, traffic for \24 subnet will come from respective links and at the time of failure of any of the link, traffic will come from other link as \22 is advertised from there :)

but i do recommend you to read more in detial about BGP before implementing and take care of other aspects also as mentioned by Amit.

HTH, pls rate if it does

rgds

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