Multihoming Internet with different IP spaces

Unanswered Question
Feb 28th, 2008

I have two different ISP's connected to seperate routers, and multiple IP blocks with your typical BGP configuration for failover.

My issue is that one of my /24 networks sends and recieves more traffic than some of my other networks, and one of my Internet connections is less used than my primary connection.

I have configured by prepending the as-path that inbound traffic to that block comes in my less used ISP and in a failover fails to my other ISP.

What I cannot seem to get to work is outbound traffic sourced from that network to the Internet. I do have it working with Policy-Based Routing, but if one of my ISP's fails then PBR just keeps looping between my routers as I have my policy looking on my ethernet interfaces.

Wanted to see if anyone had any ideas on how best to accomplish this.

I had looked at OER, but I am not sure I am ready to put that into production yet unless someone convinces me otherwise.

Thanks in advance.

Kevin

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
Mohamed Sobair Thu, 02/28/2008 - 15:12

Hi Kevin,

I just wanted to know how you make it work with PBR, as PBR has completely different approach.

you are sending BGP routing update including AS-path attribute and NLRI using Route Filtering but with Normal PBR this couldnt be acheived.

As for load sharing with 2 different SPs, please check the bellow link:

http://www.cisco.com/warp/public/459/40.html

HTH

Mohamed

olorunloba Thu, 02/28/2008 - 15:20

If I am right, your PBR does not work when youur ISP fails, because the ethernet interface remains up. If you are happy with the PBR except for this flaw, then I will advice that you use PBR with Object tracking options. Basically, this will extend your PBR to check for connectivity using methods like ICMP or HTTP Get request.

Check

http://www.cisco.com/en/US/docs/ios/12_4/ip_route/configuration/guide/h_pbrtrk.html

As I do not have your full scenario, it is hard to suggest what else might work.

Regards

Mohamed Sobair Thu, 02/28/2008 - 15:25

The Original poster have different concern,

Pls check bellow:

My issue is that one of my /24 networks sends and recieves more traffic than some of my other networks, and one of my Internet connections is less used than my primary connection.

I have configured by prepending the as-path that inbound traffic to that block comes in my less used ISP and in a failover fails to my other ISP

HTH

Mohamed

ftikphillips Thu, 02/28/2008 - 15:48

I have solved inbound traffic flow by using the as-path to advertise better routes to this network via the lesser used ISP.

My issue is with traffic sourced from my own networks, I want it to use my lesser used ISP which is not my main ISP thus my default route does not point to this lesser used ISP. I learn of two default routes one from each ISP, but i prefer my main ISP for my default route. I am trying to send traffic sourced from one of my /24's out to my lesser used ISP. PBR solves this problem, but not in a failover.

I am going to investigate and lab EEM to try this along with one of the previously posted replies.

Thanks

Kevin

olorunloba Thu, 02/28/2008 - 16:25

Hmm, EEM. I would go with the PBR with tracking options for simplicity.

Much better, and simpler, I would recieve more specific BGP routes on the less use ISP. This would increase your usage on its outbound. By controlling the prefixes you are receiving from the ISPs, you have full control on your outbound.

ftikphillips Thu, 02/28/2008 - 19:46

PBR with tracking worked well except that it takes too long to detect whether the IP I am pinging is up or down once I shut that IP down.

chuckwilson Thu, 02/28/2008 - 21:34

You can also influence the traffic by prepending- very much like you are doing for inbound traffic, except in this case you prepend the isp's as number to his advertisement to you, thus making that isp appear 1 hop further away.

I did this on my routers and it worked well. I have a very similar setup with the exception that I am using full routes from one isp and partial from the other.

Actions

This Discussion