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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: IGPs and services?
>>>>> "nicholas" == nicholas harteau <[email protected]> writes: nicholas> I'm looking for some advice on IGP tricks such that we nicholas> can give out the same IPs for a specific service nicholas> (say...DNS) to all of our customers despite geography nicholas> and have my IGP route those packets to a regional nicholas> server, thus accomplishing some inherent level of load nicholas> balancing, and even eventually returning data based on nicholas> client geography. Assign a unique (or several uniqe...) address that the customers will use, say 1.1.1.1. Configure this address onto the loopback interface of each of the servers as a secondary address. Have the host run a routing protocol (OSPF lends itself to this nicely since the area construct us usefull) and have it inject 1.1.1.1/32 into the IGP. Then arrange so that the IGP will direct all traffic to the server within the the same area as the source of the traffic. There are several ways to do this: - filter routing updates for 1.1.1.1/32 at the area border routers. This is not so good as it would probably be good to redirect traffic to a server in another area should the local one go down for some reason. - with OSPF, configure the cost parameter on inter area links to a value larger than that associated with any intra area path -- this will make sure that a routes from one area are always preferred over inter area routes. In fact I'm pretty sure OSPF does this automatially anyways, but it's nice to have things explicitly configured like this -- your "serving" area needn't necessarily correspond with an OSPF area in this case (a single OSPF area may be divided into two "serving areas" , for example). You can achieve load balancing in a more fault tolerant manner in this way too -- say you want to load balance across two web servers, but you want one to take over all of the load should the other fail. Configure the dns to round robin on 1.1.1.2 and 1.1.1.3, say and configure both of these addresses as aliases on the loopback interfaces of both servers. The first server advertises the first address with a lower cost than the second and the second does the reverse. The difference in cost should be greater than the cost associated with the best path between the servers. What is the general feeling about running routing protocols on web/dns/mail servers? Cheers, -w -- Will Waites \________ [email protected]\____________________________ Idiosyntactix Ministry of Research and Development\
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