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Gateway Wierdness

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  • Gateway Wierdness

    Dear All,

    Hopefully someone will be able to explain to me why some weirdness is happening at a clients.

    They have 2 seperate sites with 2 exchange 2003 servers connected via vpn. The appropriate server holds the mailboxes of the users depending on which site they are homed on.

    There is one SMTP connector in one site which sends for the whole organisation. They send out through their ISP's Smart Host. Everything works perfectly except recently they got banned from the smart host for sending SPAM, which we have fixed and now everything works fine.

    The wierdness is that in the site with the smtp connector, there are 2 internet connections. One is the gateway for the exchange server and there is another which is the gateway for the file server.

    Every now and then the exchange routes routes emails out through the internet connection which is the gateway for the file server....

    Why is this? surely the server should only send email out through the connection which is it's gateway. We have hunted high and low and cannot find any load balancing in the routers or anything that would explain this behaviour. It wouldn't matter except that the file servers connection was also banned from using the smart host, but we didn't realise and some eails were being bounced.

    Anyone have any idea as to why the traffic would be routed that way?

    Any help much appreciated.



  • #2
    Re: Gateway Wierdness

    Do the two routers know about each other? Are you using any routing protocols on the two routers? Does either router have any static route to each other or any other host or network?

    Here's what I would do:

    Run a packet sniffer on the Exchange server and look for ICMP redirects coming from it's gateway router. What I'm thinking is that when the Exchange server sends outbound email it sends it to it's gateway router but that sometimes, for some reason, the router thinks that the other router has a better path to the destination and is redirecting the Exchange server to use the other router. It sounds kooky but it might be the cause of the problem.