I don't see how round robin DNS will be effective here. If one of the gateway servers is down, DNS will still respond with the A records for that server.
DNS round-robin (multiple A records for gatewayout.domain.tld) is very effective in dumbly distributing the outbound load, within 2% in my measurements, between x number of gateways. ie, if the outbound load is 3000 msgs/hour, each of 3 gateway machines in the A record set for gatewayout.domain.tld will handle 1000 msgs +/- 2% max.
I have a proven, software-only solution that removes a dead gateway's A record from the gateway's record set. This adds some intelligence to the dumb load distribution, but is still not intelligent load balancing.
The gateway machines remaining after 1 is taken off-line must be able to support the increased load. In practice, if x machines are needed to support the load, you need (x+1) machines so "-1" machines leaves x. Simple redundancy.
My solution also works for inbound traffic distributed across several machines. Contact me if interested. Len _____________________________________________________________________ http://IMGate.MEIway.com : free anti-spam gateway, runs on 1000's of sites To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
