DSL and ISDN routing

[Guest]

This is my situation:
DSL router connected to Internet with dynamic IP - registered at dyndns.org
ISDN modem with fixed IP on the Internet.
ISDN modem is operated by W2K server with RRAS
behind rras is mail server on another w2k server DC
RRAS has setup port forwarding for webmail and smtp access
Workstations are also behind same RRAS server
DSL router is in the same subnet as all servers and workstations

What I would like to achieve:
to use ISDN only for SMTP connections by other mail servers
to use DSL router for all other traffic originating from any server or
workstation or the Internet (in case of webmail)

If I understand it correctly it requires port based routing because Internet
host may come in through two doors: ISDN modem on port 25 and webmail on port
443

How do I solve that?

 

[Phillip Windell]

What I would like to achieve:
to use ISDN only for SMTP connections by other mail servers
to use DSL router for all other traffic originating from any server or
workstation or the Internet (in case of webmail)

Then your routing of the LAN needs to go "outbound" on the DSL Device.

If I understand it correctly it requires port based routing because Internet
host may come in through two doors: ISDN modem on port 25 and webmail on port
443

No. The internet host will always come in on the IP# that is associated
with the MX DNS Record which will only be one IP# and will be the one of the
ISDN line. However keep in mind that some foolish Admins out there in
Internet-Land still use Reverse-DNS Lookups to fight SPAM,...since the
source IP# of you outbound mail will always be the DNS Line it will not
match the Reverse-Lookup and will be rejected. There is nothing you can do
about that with this kind of situation. The best solution is to forget this
whole "two line" thing and run a single fast Line with a static IP#.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com
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Understanding the ISA 2004 Access Rule Processing
http://www.isaserver.org/articles/ISA2004_AccessRules.html

Troubleshooting Client Authentication on Access Rules in ISA Server 2004
http://download.microsoft.com/download/9/1/8/918ed2d3-71d0-40ed-8e6d-fd6eeb6cfa07/ts_rules.doc

Microsoft Internet Security & Acceleration Server: Guidance
http://www.microsoft.com/isaserver/techinfo/Guidance/2004.asp
http://www.microsoft.com/isaserver/techinfo/Guidance/2000.asp

Microsoft Internet Security & Acceleration Server: Partners
http://www.microsoft.com/isaserver/partners/default.asp

Deployment Guidelines for ISA Server 2004 Enterprise Edition
http://www.microsoft.com/technet/prodtechnol/isa/2004/deploy/dgisaserver.mspx
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