At 00:09 3/13/2005, Kroll, David wrote: >This is a Win2003 DNS issue. >Some mailservers behind firewalls which do not allow transfer of UDP packets >larger than 512 bytes may not be able to return the MX record > >If your firewall restricts UDP packet transfers though, you may want to >verify that it will allow transfer of a MX record within the size >limitations specified by RFC1035: > >http://www.faqs.org/rfcs/rfc1035.html > >Windows 2003 server has included Extension Mechanisms for DNS (EDNS0) to >allow larger packets. If you run this command on a 2003 server: "dnscmd >Server Name/Config /EnableEDnsProbes 0", it fixes it without making any >changes to the firewall.
OK, did I miss something, or have UDP-based DNS messages been changed since the last time I looked? <checks RFC1035> Nope... Still a 512 octet message length (section 2.3.4). Any UDP-based DNS message longer than that is not RFC compliant, and (IMHO) should be blocked. That's why there's a method to fall back to TCP when there's more data to be returned than will fit in a 512 octet message.... If there's an RFC that allows larger packets in UDP, could you reference it please? - To unsubscribe from this list: send the line "unsubscribe xmail" in the body of a message to [EMAIL PROTECTED] For general help: send the line "help" in the body of a message to [EMAIL PROTECTED]
