Multi-Homed Network, Backup -Net To Servers Question

[CaffieneNnicotine]

The non profit organization I work with has a web server iwht about 3 sites hosted on it. In the very near future that size will increase to 25 or more. Currently we have a 1.5Mb DSL pipe from our local carrier. The quality is very good but since we will be hosting several sites, the powers that be would like to have a backup internet connection. I have procured another DSL line from the same provider, but which runs on an entirely different network with different IP's, gateways and all. Now the question: When the primary link goes down, and the failover kicks in, how can I advertise the new default route to the ISP routers to our web server? I have heard rumors about BGP, but details are fuzzy at best. Is advertising a new default route the answer? Or should I look into some sort of Dynamic DNS (I dont think so). Thank you very much for any help you can give. This question is DRIVING ME INSANE!!!

Sincerely All Complaints Will Be Routed To /dev/null

 

[ccie9545]

Using BGP would work. But, you would have to make sure that your ISP would allow you to run it, and peer with their routers. Plus there are certain precautions that you would want to take when using BGP in a multihomed situation

If you are truly just going to use the alternate DSL link as a backup, and nothing else, then you might want to think of alternatives to bgp. whether that alternative is dynamic dns, you would have to decide. i guess one determining factor is going to be whether or not you are going to keep the same IP addresses on the web server when the primary link goes down and the secondary link kicks in. If the address is going to be the same then dynamic dns wouldn't do you any good, and you would have to figure out a way to advertise the alternate route to the internet. whether that is bgp would be up to you and your provider. if the addresses are going to be different then you could consider dynamic dns, but you will still have to determine a method to advertise the addresses to the internet.

hope this helps.
Erik Rudnick, CCIE No. 9545
mailto:erik@kuriosity.com

 

[CaffieneNnicotine]

Thanks for your response. I am curious as to what precautions I would need to take to implement BGP. Getting our ISP to let us talk to their routers won't be a problem (knowing their cheif engi has its advantages). Chances are that both DSL interfaces will have the same outside ip's and I will set up load balancing across them to virtualy double our throughput, which is another benefit of BGP if I am not confused. Any suggestions?

Thanks! All Complaints Will Be Routed To /dev/null

 

[ccie9545]

If isn't necessary for you to actually run BGP. Rather, the provider will advertise the available networks to the Internet and the Internet can choose which path is the shorter of the two to get to your webservers. You would need only default routes pointing out to your provider.

If you do decide to run BGP (probably not the most efficient or recommended solution) then you will want to make sure that you do not become a transit path for traffic that does not originate, or is not destined for your networks. This is done by filtering, and is not too difficulut to set up. Plus, you would probably only want to have your provider advertise default routes to you, and you would advertise the required networks. Again, BGP is not necessary, and isn't really recommended in this situation.

Your best bet, and probably the easiest to configure and the easiest to maintain, would be to just set up the second link and have a couple of default static routes pointing to the two different gateways.

Hope all goes well, let me know if I can help...

Erik Rudnick, CCIE No. 9545
mailto:erik@kuriosity.com