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Two ISPs: Failover smtp routing HOWTO?

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Two ISPs: Failover smtp routing HOWTO? - 3.Jan.2008 4:16:07 AM   


Posts: 1
Joined: 10.Sep.2005
Status: offline
Hello all,

Our Exchange server uses our ISP's smtp server as a 'smart host'. I would normally prefer Exchange to route outgoing mail directly but there are a couple of reasons why the current setup is desired.

I now want to add a redundant internet connection to a different ISP for my network. I'll be using a NETGEAR FVS124G DUAL WAN router in failover mode.

Both ISPs require that connections to their smtp server be made from inside their network, so I'll need to use alternate smtp servers depending on which WAN link is active.

Is there a way of retaining the smart host configuration in my proposed setup?

Thanks in advance,

Post #: 1
RE: Two ISPs: Failover smtp routing HOWTO? - 3.Jan.2008 1:26:25 PM   


Posts: 2516
Joined: 1.Dec.2005
From: Centreville, Virginia
Status: offline
You can create two smtp connectors with different costs. But it will not do automatic fail over. Redundant SMTP connectors only safeguard against your bridgehead going down. Not your ISP going down. If your bridgehead is up; the link is considered up whether or not the ISP link is down.

Configuring Connectors for Failover

If you want to configure connectors to failover automatically, you can create two separate connectors on different bridgehead servers, each with a different cost. Link state for a connector is determined by its local bridgehead server. If the bridgehead server on the preferred connector with the lowest cost is unavailable, that connector is considered unavailable and routing automatically chooses the second connector. When the bridgehead server hosting the connector with the lower cost becomes available, Exchange servers then begin using it again.
If you use two connectors with the same cost, Exchange servers will randomly pick which bridgehead server and connector they use, and if this bridgehead server becomes unavailable, they will fail over to the second connector. However, once the first bridgehead server becomes available, the servers will not failback to this server because the route has the same cost as the server they are already using.
Advanced Routing Configuration

James Chong (MVP)
MCSE | M+, S+, MCTS, Security+

(in reply to ilanlchait)
Post #: 2

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