We currently have two DNS servers : brainy1.ie-eg.com and brainy2.ie-eg.com We want to add a new DNS server brainy4.ie-eg.com
it would be even brainier if you read rfc 2182 section 3, and put at least one server at a tolpologically and geographically diverse location.
A pointer to a best current practice document is always helpful. RFC 2182 is getting old, I guess I'd also recommend that recursion is disabled on the servers. A "dig version.bind txt chaos @brainy1.ie-eg.com" returns 8.2.3-REL-IDNS. If this is an unpatched version you might want to read http://www.isc.org/products/BIND/bind-security.html. I still wonder why so many DNS operators don't pay attention to RFC 2182. Lots of domains have all their nameservers in a single AS. The worst example for what can go wrong I've seen so far was the trouble of web.de (a large freemailer in Germany) back in the last summer: They were multihomed but had both nameservers only connected via AS517. The KPNQwest network went suddenly down and both servers were unreachable. IIRC web.de somehow managed to get an "emergency rebuild" of the .de zone from DENIC. Did they learn something from this sad event? Nope: Both servers are again connected via a single AS. Joerg