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ISA2006 - controlling what IP address is used for outbound communications?

Posted on 2009-02-09
Medium Priority
Last Modified: 2013-11-16
I have a multi homed ISA2006 in a small network as the edge firewall.  There are 5 routable public IPs attached ( - 105) to the external NIC,  and 1 IP ( on the interenal NIC with the LAN and clinets/servers behind the internal NIC (192.168.0.n). addressing scheme.
I need to get an internal server on (behind the isa server)  to communicate with an external network over a specified IP address  on the isa server's external NIC for example

Q. Is there a way to force a connection to the external network that uses a speciified IP address from the 5 externally bound addresses on the ISA server ?
Question by:martinmcginley
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Expert Comment

by:Keith Alabaster
ID: 23592760
No - not supported Martin - the outbound NAT will always use the first ip listed

Author Comment

ID: 23592770
ok - just to verify whatever of the 5 ips is listed first is the ip used as the outbound ip - right ?
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Accepted Solution

Keith Alabaster earned 2000 total points
ID: 23592806
That is the way it is written, yes. On certain boxes, this shows itself as the ip that is actually bound to the nic being the one that is always used. ie the machine, for some reason, differentiates between the actually bound ip address and the (in your case) four additional addresses which are just arp addresses.
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LVL 51

Expert Comment

by:Keith Alabaster
ID: 23592815
Bottom line, you cannot create rules that allow http to go out one address and smtp to go out on another address, for example.

Author Closing Comment

ID: 31544520
thanks - i got it
LVL 51

Expert Comment

by:Keith Alabaster
ID: 23593714

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