Hi,

At my work, we have an ISP that provides us with 2 connections with different IP addresses but at the moment they don't switch automatically if one fails, and can only work for outbound traffic.

I tried to automate this with floating routing table on a CISCO 1711 router but then switching to the second link only happens when there's no longer a signal on the cable that's plugged into the router's interface directly -- and the failure most often happens somewhere in the middle. And that also does not make us available from outside.

Can anyone suggest a better way? Maybe an outside DNS server can have a second IP address recorded for our domain name?

I found somewhere suggestions that a loadbalancer could solve that but these appliances are way too expensive.

I also thought about using BGP but my router's RAM (128MB) is too small for the global routing table that BGP requires. And I also need an ISP (or better 2 ISPs) that provide BGP service. Before trying to convince others that we need to invest more into this, I'd like to know whether there are no easier ways.

So, what would you suggest?

Hello,

Here are some links that might be of interest:
Load Balance Failover MultiWAN
Linux Failover Router
Never done something like this myself so can not elaborate.

Hope it helps.

Kind regards,

Eric

Thank you, the articles look promising, I'll read them.

Hi,

You're welcome, I hope they can provide a solution for you. I'd appreciate it if you could post your findings and/or results here too. That way others that face the same problem/question can take advantage of your experiences.

Kind regards,

Eric

So, I read these. The "Using a Linux failover router" at linux.com seems to suggest a solution where a router reacts on the availability of immidiate connection, which, as I already told, I have done (though in different ways) with my router, and which is not enough because the problems usualy are somewhere in the ISP's networks.

"Load Balancing & Failover With Dual/ Multi WAN / ADSL / Cable Connections on Linux" and its followup "How To Configure Dual ADSL / Cable Connections, Firewall, Gateway / NAT With Shorewall Firewall on Linux" would perhaps be ideal if only outbound traffic was the concern.

So I'm still looking for solutions.

I would attack this from a network (Cisco) perspective rather than a Linux one.

You say you have a single ISP providing two circuits, each with a dedicated IP(s), and most times you find the problem to not be directly with hardware in your office. What is the handoff type (T1, Ethernet, etc.)? My concern would be if you have two circuits going to the same ISP core if they are having routing problems in the cloud both connections would be impacted.

What services do you have with inbound connections? Something like email will be easy to setup using two different IPs (just add a second MX record pointing to a different IP that ultimately NATs to the same server). Web service is more difficult because if DNS has multiple IPs for a site some users will get the IP which is down at times.

Also just an FYI BGP doesn't require that you do a full routing table. You can use BGP to advertise a network (most carriers want a /24 for this) through multiple different ISPs for redundancy. You can accept only a default route inbound and let your ISP route traffic for you.

DNS will provide all the IP addresses, and modern web browsers will try every address until connection is successful. If no response is received (rather than an ICMP error) this will take a long time.