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(ASCEND) P75, NAT, strange routing behaviour



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Hi:

I m attempting to do something "funny" with my Ascend Pipeline 75, and am
seeing strange routing table behaviour.  Here s my situation:

I ve got a 1B connection profile to my ISP, Insync.net, with a statically-
assigned two-bit subnet.  My P75 is capable of correctly bringing this
connection up and tearing it down.  Everything with this connection is
hunky-dorey.

I am in the process of configuring a _second_ connection, to my employer
via their remote access equipment.  This connection is NAT (has to be NAT), 
to a private (192.x.x.x/24) subnet which is firewalled from the rest of the 
net.  This connection, in and of itself, is functioning.


Here s what the connections look like:

   Internet                                                 Internet
      |                                                        |
      |                                                        |
      |                                                     Firewall
      |                                                        |
      |                                                        |
     ISP------------------------- P75 ----------------------- Work

  Net:204.253.208.0/24    Net: 204.253.212.108/30   Net: 
  GW: 204.253.208.10       


The problem:

Because of the firewall on my employer s network, and performance reasons,
I would like to route _all_ IP traffic which is destined for the
net-at-large (anywhere _but_ my employer s subnet), through my ISP
connection, even if it is necessary for the router to bring the connection
to my ISP up to route traffic.

No problem, right, just plug in a default static route to
204.253.208.10/24, like:

Destination       Gateway               
0.0.0.0/0         204.253.208.10   <pref>  <metric>

Here s my whole routing table, (with NAT routing turned off, wanidle0 is
the connection profile to my employer s subnet):

Destination        Gateway         IF       Flg   Pref Met     Use     Age
0.0.0.0/0          204.253.208.10  wan7     SG       1   1     206    1731
127.0.0.0/8        -               bh0      CP       0   0       0   17703
127.0.0.1/32       -               local    CP       0   0       0   17703
127.0.0.2/32       -               rj0      CP       0   0       0   17703
192.168.56.0/24    192.168.56.11   wanidle0 SGP    150  10       0     547
192.168.56.11/32   192.168.56.11   wanidle0 SP     150  10       1     547
204.253.208.0/24   204.253.208.10  wan7     rGTM    10   1      28    1668
204.253.208.0/24   204.253.208.10  wan7     SGM     10   1    2220   17703
204.253.208.10/32  204.253.208.10  wan7     rTM     10   1      72    1668
204.253.208.10/32  204.253.208.10  wan7     SM      10   1     188   17703
204.253.212.108/30 -               ie0      C        0   0   58221   17703
204.253.212.109/32 -               local    CP       0   0   20582   17703
209.113.65.0/24    204.253.208.10  wan7     SG     100   1       8   17703
224.0.0.0/4        -               mcast    CP       0   0       0   17704
224.0.0.5/32       -               bh0      CP       0   0       0   17704
224.0.0.6/32       -               bh0      CP       0   0       0   17704
224.0.0.9/32       -               local    CP       0   0      58   17704
255.255.255.255/32 -               ie0      CP       0   0       0   17704
   


Unfortunately, when the router, running either 6.1.3 or 6.1.5, brings up the 
NAT connection to my employer s net, it replaces the default route with one to
my employer s subnet, causing everything except traffic which is specifically 
destined for my ISP, to be routed through my employer s net.  Even worse, 
this route is not removed from the routing table when the connection to my 
employer s net is torn down.  Thus, the router thinks that all traffic should 
be routed through my employer's net, now and forevermore, amen! :-)


Here s the routing table with NAT routing turned on, and the connection to
my employer s net up:

Destination        Gateway         IF       Flg   Pref Met     Use     Age
0.0.0.0/0          192.168.56.11   wan8     Sn     100   1       0       6
127.0.0.0/8        -               bh0      CP       0   0       0   18068
127.0.0.1/32       -               local    CP       0   0       0   18068
127.0.0.2/32       -               rj0      CP       0   0       0   18068
172.18.250.63/32   -               local    rPTn   100   0       0       6
192.168.56.0/24    192.168.56.11   wan8     rPTn    10   1       0       6
192.168.56.0/24    192.168.56.11   wan8     *SGP   150  10       0     912
192.168.56.11/32   192.168.56.11   wan8     rPTn    10   1       0       6
192.168.56.11/32   192.168.56.11   wan8     *SP    150  10       1     912
204.253.208.0/24   204.253.208.10  wan7     rGTM    10   1      29    2033
204.253.208.0/24   204.253.208.10  wan7     SGM     10   1    2220   18068
204.253.208.10/32  204.253.208.10  wan7     rTM     10   1      87    2033
204.253.208.10/32  204.253.208.10  wan7     SM      10   1     199   18068
204.253.212.108/30 -               ie0      C        0   0   59031   18069
204.253.212.109/32 -               local    CP       0   0   20777   18069
209.113.65.0/24    204.253.208.10  wan7     SG     100   1       8   18069
224.0.0.0/4        -               mcast    CP       0   0       0   18069
224.0.0.5/32       -               bh0      CP       0   0       0   18069
224.0.0.6/32       -               bh0      CP       0   0       0   18069
224.0.0.9/32       -               local    CP       0   0      71   18069
255.255.255.255/32 -               ie0      CP       0   0       0   18069


And, here s the routing table with NAT routing turned on, and the
connection to my employer's net down:

Destination        Gateway         IF       Flg   Pref Met     Use     Age
0.0.0.0/0          -               wanidle0 Sn       0   1       0      13
127.0.0.0/8        -               bh0      CP       0   0       0   17991
127.0.0.1/32       -               local    CP       0   0       0   17991
127.0.0.2/32       -               rj0      CP       0   0       0   17991
192.168.56.0/24    192.168.56.11   wanidle0 SGP    150  10       0     835
192.168.56.11/32   192.168.56.11   wanidle0 SP     150  10       1     835
204.253.208.0/24   204.253.208.10  wan7     rGTM    10   1      29    1956
204.253.208.0/24   204.253.208.10  wan7     SGM     10   1    2220   17991
204.253.208.10/32  204.253.208.10  wan7     rTM     10   1      85    1956
204.253.208.10/32  204.253.208.10  wan7     SM      10   1     195   17991
204.253.212.108/30 -               ie0      C        0   0   58698   17991
204.253.212.109/32 -               local    CP       0   0   20702   17991
209.113.65.0/24    204.253.208.10  wan7     SG     100   1       8   17991
224.0.0.0/4        -               mcast    CP       0   0       0   17991
224.0.0.5/32       -               bh0      CP       0   0       0   17991
224.0.0.6/32       -               bh0      CP       0   0       0   17991
224.0.0.9/32       -               local    CP       0   0      68   17991
255.255.255.255/32 -               ie0      CP       0   0       0   17991


In both cases above (NAT routing ON, employer's wan connection either up
or down, I'd like the default route to remain set to:

Destination        Gateway         IF       Flg   Pref Met     Use     Age
0.0.0.0/0          204.253.208.10  wan7     SG       1   1     206    1731

Is there any way I can accomplish what I m looking to do, other than
manually turning off NAT when I don t need/want to connect to my employer
?

Thanks muchly!


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=======================================================================
Greg R. Broderick           AT&T is reportedly interested in buying
                            America Online. If this occurs, federal
                            regulators are concerned the merged
                            corporation will have a total monopoly on
                            busy signals.
ganymede@insync.net
greg@qrd.org
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