[NTLUG:Discuss] Re: using the dsl and dial up connections at the same time -- 3 fold problem

[Bryan J. Smith]

Let me revisit this and point out the 3 things you need to do:  

  1.  Establish the dial-up link and subnet
      (regardless of call/answer direction)

  2.  Establish an additional route to the subnet from the LAN
      (on the node on the LAN that talks to the remote node)

  3.  Distribute that route to the rest of the LAN
      (so LAN systems can access the dial-up node)

#1 is easy.

Unfortunately, default scripts for #2 in PPP and others typically assume
it is the "default gateway."  While this _can_** be the case in the
remote node to the LAN (although that's not ideal**), it is not so for
the node on the LAN that is talking to the remote node.

And if any other system on the LAN is going to talk IP to that remote
node _other_ than the one with the modem, then you need #3.  You can
either do that _manually_ on each system, or you can use a dynamic
routing protocol like RIP or OSPF to distribute it.

-- Bryan, CCDP (again, not that it matters)

**NOTE:  Even if everything goes through its dial-up to the remote LAN
from the standpoint of the remote node, you want to list _all_ routes. 
That includes a route to the LAN (metric 1) _and_ the "default gateway"
(metric 2).  Otherwise you will have ARP overhead that you do not want.
-- especially if you plan on putting additional systems behind that
remote node.


-- 
Bryan J. Smith                                  b.j.smith at ieee.org 
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