Multihoming, Single Router, 2 ISPs, No BGP

[TheDukeofBaghdad]

Hi Friends,

My boss wants me to configure load balance on one of our customer sites:

1. I want to know if this is possible or not (With the below conditions)?
2. If yes, could you explain it to me, provide an example or link to a page that helps me do the configurations?

The 2 ISPs are connected to a single router Cisco1841 via two different interfaces, the Cisco1841 is running IOS 15.1(4)M10.

The 2 ISPs are using different Public IP Addresses and providing us EACH with 5 Static IP Addresses (1 for the router and the other get mapped using NAT to private IP Addresses on the system).

I have to configure NAT/PAT to the two ISPs for load balance. (Done!)

I have to configure Static NAT to allow SSH connection from the internet to the 5 static of any of the ISPs to connect to the same machines.

We are NOT running BGP and we have to do it using static routing.

In case one of the ISPs failed we need to reroute all the traffic to the other ISP.

I have configured the NAT/PAT to the two ISPs and it's working!

I have configured the Static NAT from the two ISPs toward the same machines but currently, it's only working through one ISP!!! (This is the main issue that we need to fix)

Thanks

[Reza Sharifi]

Hi,

If you are not running BGP, you can accomplish the same thing with static routes.  Point one static route to next hop IP and the other static route to the other next hop address. The traffic should load balance and if one of the providers fails, the other one will route all traffic. This will be an active/active configuration. You can also do an active/stand-by configuration where the primary providers always forwarding traffic and the other one on stand-by until the primary fails. In the second scenario the second static route needs a high AD.

HTH

[TheDukeofBaghdad]

Hi Reza,

Thanks for your comment.

Yes, I have done that and it's working great the problem is with the static NAT only one set of public IP Addresses are responding to the requests!

I can reach only the public IP Addresses of the router through ISP1!

ISP2 can provide with full access to all 5 of my static IP Addresses!

[Reza Sharifi]

Hi,

Ok, so for NAT you can simply use one set of IP address for both providers. As for the other set of IPs from the other provider, you can use that for something else like DMZ.

You would need to tell both providers that you are going to be advertising a second set of subnet to them in case of fail over, so they can in turn advertise it for you, if not a provider usually advertise the IP they gave you.

HTH