News Group Posts

routing

From: Tony Lawrence <tony@aplawrence.com>
Newsgroups: comp.unix.sco.misc
Subject: Re: Routing question
Date: Fri, 28 Sep 2001 16:09:38 GMT

Jeff Liebermann wrote:
> 
> 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:

Yes, but there's no particular reason that he needs two dialups- I've set up
plenty of situations like this where the mail isp is different from the
internet access isp- especially since it's smtp, there should be absolutely
no reason he can't do this.

He needs an inbound nat translation (who knows what they might call it on the
router, but it doesn't matter- port 25 on some public address redirects to
some internal address).  He sends the etrn out over the internet link and it
responds.. no issue.

Somethings set up wrong somewhere..

-- 
Tony Lawrence (tony@aplawrence.com)
SCO/Linux articles, help, book reviews, tests, 
job listings and more : 
 

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