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Today's Topics:
1. ADSL Routers and multiple Port 25 forwarding (John Morch)
2. Re: ADSL Routers and multiple Port 25 forwarding (Mark Foster)
3. Re: ADSL Routers and multiple Port 25 forwarding (Craig Whitmore)
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Message: 1
Date: Sat, 06 Jan 2007 15:36:42 +1300
From: "John Morch" <morchjohn@hotmail.com>
Subject: [adsl] ADSL Routers and multiple Port 25 forwarding
To: adsl@lists.unixathome.org
Message-ID: <BAY7-F119DD1D9613CEFD307E420B7BE0@phx.gbl>
Content-Type: text/plain; format=flowed
I have two adsl connections with fixed ip addresses.
I forward port 25 to server1 on first one using XH1169 and do heavy spam
filtering.
I used to forward port 25 on the second to server2 using M1122 but stopped a
while ago as dont have any good spam filtering on server2.
all MX records are set to go to one or the other fixed ip addresses with the
other as a secondary.
Both servers pass traffic internally for appropriate domains.
Last night adsl1 fell over and no email was delivered (as expected)
I have tried forwarding both adsl routers to server1 but it is sbs2003 and
will not allow this it seems.
Can anyone suggest how i can forward port 25 from M1122 to XH1169 and then
onto server1 or if not possible I have a spare G604T that i can use in place
of the M1122.
There is no need for other port forwarding on adsl2
Thanks in advance
John
_________________________________________________________________
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------------------------------
Message: 2
Date: Sat, 6 Jan 2007 17:11:30 +1300 (NZDT)
From: Mark Foster <blakjak@blakjak.net>
Subject: Re: [adsl] ADSL Routers and multiple Port 25 forwarding
To: John Morch <morchjohn@hotmail.com>
Cc: adsl@lists.unixathome.org
Message-ID: <Pine.LNX.4.62.0701061704070.30343@maverick.blakjak.net>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> Last night adsl1 fell over and no email was delivered (as expected)
> I have tried forwarding both adsl routers to server1 but it is sbs2003 and
> will not allow this it seems.
This will probably be because its default gateway will point back to
adsl2's router, so any attempt to communicate with it through adsl1 will
have all return packets routed via adsl2 - and the remote end will not
have any idea what is going on. (Aka, no tcp sessions can be established).
> Can anyone suggest how i can forward port 25 from M1122 to XH1169 and then
> onto server1 or if not possible I have a spare G604T that i can use in place
> of the M1122.
Can't really be done, as it'd require you to be able to deal with pinholes
on the internal interface of the XH1169 and then re-forward the traffic to
a different address, via the same interface. This isn't exactly typical
behavior so I doubt the box has been configured to allow this.
If you have two mail servers with one acting as secondary MX for the other
and vice versa, the only way to force traffic to one MTA in particular
would, from my POV, be to close Port 25 on the other and/or cause the
inbound systems to talk to the preferred mail server via its own MX record
/ IP address.
The alternative would be to change the default gateway on server1 to point
to the other DSL modem. (Basically you can use only one route at a time.
To have different routes you would need different costs - one would be
preferred over the other - and the mailsystem would need to see the
preferred one actually fail / cease to be available, before it'll pick the
next lowest metric from its routing table and send traffic there.
This is similar to corporate routers (say on frame relay) which have an
ISDN link as secondary; the ISDN Link is present but has a much higher
cost, so is not used unless the primary route (the frame link) dissapears
from the routing table - eg, the interface drops.
Hope this helps. I dare say there are people on here more experienced at
some of this than I.
Mark.
------------------------------
Message: 3
Date: Sat, 6 Jan 2007 21:41:06 +1300
From: "Craig Whitmore" <lennon@orcon.net.nz>
Subject: Re: [adsl] ADSL Routers and multiple Port 25 forwarding
To: "Mark Foster" <blakjak@blakjak.net>, "John Morch"
<morchjohn@hotmail.com>
Cc: adsl@lists.unixathome.org
Message-ID: <00ca01c7316e$69c7bdd0$0301010a@me>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
>
> This will probably be because its default gateway will point back to
> adsl2's router, so any attempt to communicate with it through adsl1 will
> have all return packets routed via adsl2 - and the remote end will not
> have any idea what is going on. (Aka, no tcp sessions can be established).
There is 1 option. buying 2 more intelligent DSL routers such as a couple of
cisco 837/537 for example and use iBGP or whatever your favourite igp is and
use that to change things around automagicllly.. Also another option
depending on the routers you have is to use RIP internally on them. I know
alot of routers have RIP routing, but if its useable internally I have no
idea.
Thanks
Craig
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End of adsl Digest, Vol 2, Issue 1
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Received on Sat Jan 6 12:00:06 2007