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From: dkrapf@access1.digex.net (Don Krapf)
Newsgroups: comp.os.386bsd.questions,alt.winsock
Subject: Re: Routing Problem
Date: 24 Sep 1994 04:01:03 -0400
Organization: Express Access Online Communications, Greenbelt, MD USA
Lines: 69
Message-ID: <360mbv$73q@access1.digex.net>
References: <35kaui$ph9@herald.indirect.com>
NNTP-Posting-Host: access1.digex.net
In article <35kaui$ph9@herald.indirect.com>,
Thomas D. Simes <tsimes@bslnet.com> wrote:
>Hello all!
>
>We are having a puzzling routing problem at our site - at least I
>think that it is a routing problem. Here is the situation:
>We are running a 386bsd 1.1.5.1 box as an Internet node with
>modems attached for dial-in service. This bsd box is attached
>to the net using a router and CSU/DSU running frame relay to
>our provider. Both the router and bsd box can ping each
>other and the net without a problem. The problem comes
>when I SLIP into the bsd machine using Trumpet winsock 1.0a.
>While the SLIP'd machine and the bsd box it is attached to can
>ping each other, the SLIP'd machine cannot see our router or
>the rest of the net (naturally). So far I have tried the
>following to no avail.
The problem is that nothing on your local net knows that it
must send packets to the SLIP gateway in order to get them
to the destination. When the router (for example) wants to
send a packet to one of the SLIPped in machines, it looks
up the machines IP address in its routing table and gets a
match on the network number which tells it that the destination
is on the local net. Then it arps for the destination but
the arp goes unanswered.
You can fix this in any of three ways:
1 Let the SLIP gateway proxy arp for the SLIPped machines.
I run MoringStar PPP on my SCO SLIP gateway. It lets me
automatically run a script whenever a SLIP/PPP connection
is started or stopped. In the start script I do
"arp -s ..." to add the remote machine to the arp table
and in the stop script I do "arp -d ..." to remove the
remote machine from the arp table.
2 Use a seperate subnet for the SLIPped machines.
By putting the SLIPped machines in there own subnet
you can do subnet routing and let the SLIP gateway
advertise a route to it. Remember that the addresses
with a subnet part of all ones or all zeros are
reserved so that you must have at least two bits of
subnet which leaves you with only 6 bits for the host.
This give you two useable subnets with up to 62 hosts
each. To lose a smaller part of your address space
to the reserved subnet numbers you can make the
subnet field wider but then you end up with a lot
of little subnets.
3 Give each machine on your local net a static route
through the SLIP gateway for each remote machine.
While this is probably not a practical solution,
it is a good way to check that I've correctly
diagnosed the problem. SLIP into your SLIP gateway
and verify that the remote machine and the gateway
can communicate with each other. Then, go to the
router and give it a specific route for the remote
machine through the SLIP gateway. It will use this
preferentially over the network route. Your remote
machine should then be able to communicate with
the router and with the internet beyond.
Don