routing

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From - Fri Sep 28 12:03:09 2001
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From: Jeff Liebermann <jeffl@comix.santa-cruz.ca.us>
Newsgroups: comp.unix.sco.misc
Subject: Re: Routing question
Date: Fri, 28 Sep 2001 07:30:18 -0700
Organization: Committee to Maintain and Independent Xenix
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On Fri, 28 Sep 2001 08:29:16 +0100, "David Nash"
<nashcom@btinternet.com> wrote:

>Hi
>
>I posted a question a couple of weeks ago about retrieving SMTP mail from an
>ISP using a Windows NT server.  Thanks for the replies.  For those that are
>interested, and before I ask another question, the ISP needs to allocate a
>fixed IP address to the WAN port of the ISDN router.  The router then has to
>have 'Port Address Transalation' so that the ISP can connect to port 25 of
>the router WAN address, and this is then translated to port 25 of your SMTP
>Exchange server.  Basically, when you deliver outgoing mail to the ISP using
>SMTP, you need to send an ETRN command that requests the SMTP server at the
>ISP to send your incoming mail to your server.  Sounds complicated, but I
>thought it may be of interest/use.
>
>However, we have two ISPs, one for the email, and a 'free line' for the
>Internet.  If I configure the Port Address Translation so that the email can
>work, the call to the Internet ISP doesn't work properly.  I'm thinking
>about maybe adding a second router and splitting the Internet/Email, but I'm
>not sure how to route Internet through one router and email through the
>other.  The default gateway is set to the existing router.  I've tried
>configuring the router so that traffic destined for the Mail host brings up
>one 'autocall', and the Internet traffic brings up the free autocall, but as
>I say, it seems the the NAT for the fixed WAN IP address is causing
>problems.
>

I wish you wouldn't:
1.  Assume that I've read your un-referenced previous posting.
2.  Refuse to disclose any numeric information such as the make and
model of your firewall.
3.  Not post any diagnostic output such as your router table.

You cannot dial two ISP's and still have a fixed default route.  That
will not work.  When you dial ISP#1 for email, the default route will
need to point to that ISP's gateway.  When you hangup and dial ISP#2
for cruising the internet, the default route will need to move to that
ISP's gateway.  Try:
   route delete default xxx.xxx.xxx.xxx
   route add default xxx.xxx.xxx.xxx
No need to reboot.  Check the results with:
   netstat -rn

I would look into staying connected with ISP#2 and just picking up
your email via SMTP from ISP#1.  I do this all the time.  I have
something like 8ea email accounts, all of which I can pickup from any
ISP.  How you connect to the internet is different from what services
you use once connected unless you're dealing with a proxy server).

Some ISDN firewalls allow for multiple ISP's and include provisions
for moving the default route.  Just about any NAT firewall will do
this.  Just point your servers default route and DNS server to your
unspecified router/firewall and let it do all the dirty work.


-- 
Jeff Liebermann  150 Felker St #D  Santa Cruz CA 95060
(831)421-6491 pgr (831)426-1240 fax (831)336-2558 home
http://www.LearnByDestroying.com   WB6SSY
jeffl@comix.santa-cruz.ca.us   jeffl@cruzio.com
 

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