Single site two 5.5 servers use WAN to talk.

[gorskel1]

I have a strange problem. I have two 5.5 servers on one site on an internal LAN. Each server is running IMS (Internet Mail Service) with its own connection to the internet (one cable, one DSL). There is a firewall on each server. One of the purposes of this set up is a redundant connection to the internet so that mail still comes in when either one of the two connections is down. Everything worked fine until I "upgraded" one server from NT to W2K (actually fresh install of both W2K and Ex5.5). DNS MX entries are the same and are fine. Both servers see each other, etc., except for ONE thing. Now the 2 servers communicate with each other ONLY when I make a hole through both firewalls for their respective external IP addresses. Without the "whitehole", I get RPC communication errors recorded in the event log. This means that they communicate with each other via the WAN, not the LAN. I need them to communicate via their internal IP addresses, so that when one of the two internet connections is down, both servers receive mail. Until the W2k upgrade, everything worked fine without whiteholes through the firewall - they used to communicate fine via the internal LAN. Something changed which makes the servers look for each other via the WAN instead of the LAN. At this point, I do not know where to start to troubleshoot this. Any help will be appreciated.

 

[brontosaurus]

I'm not 100% sure I understand what happened here, but it's possible, depending on your IP addressing and DNS setup, that the W2K box sees the other server as an "outside" domain (due to DNS). If you could give a little more info about your IP addressing, DNS, WINS, and domain names, it would clear things up a bit...

 

[gmanboston]

As soon as you install Exchange 5.5 on W2K, with the intermet mail services, it requires you to use a fully qualified domain name instead of using a plain old Netbios name. The communication (RPC) is getting broken from the NT4 server to the W2K server and the way to resolve it is to either configure a reverse DNS lookup internally to the W2k Exchange server or on the NT 4 server configure an LMHOST entry to reflect the FQDN of the W2K server

On NT4 server configure LMHOST entry pointing to W2K server.

EX:

192.168.100.1 server name.domain name.com #mailserver

Once you do this you should be able to ping the W2k server by the using the FQDM from the Windows NT4 server. RPC/MTA errors should subside from both servers

 

[gorskel1]

Gman from boston! You're the Man!
Your solution worked perfectly - only the file entry needs to be a HOSTS file entry rather than an LMHOSTS entry. Maybe that is what you meant, but I misunderstood. Anyway, thanks a million!

By the way, when I upgrade the NT server to W2K, I should not need the HOSTS entry anymore?

 

[gmanboston]

As long as you have an internal DNS server to resolve the FQDN.

Take it easy