[lug] local network

[rm at mamma.varadinet.de]

On Sat, Jul 21, 2001 at 05:03:01PM -0600, D. Stimits wrote:

> I don't do this often enough to lead directly to any answers, but the
> next thing is probably to question routes. If you type (as root)
> "route", it'll show routing info. If you have an incorrect netmask
> (column Genmask in route output) for the eth0, this would cause a
> problem. In some cases if a default route also has an incorrect netmask,
> it might cause failure while ppp0 is up. Here is a typical route output:
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> your.isp.com    *               255.255.255.255 UH    0      0        0
> ppp0
> 10.0.0.0        *               255.0.0.0       U     0      0        0
> eth0
> 127.0.0.0       *               255.0.0.0       U     0      0        0
> lo
> default         your.isp.com    0.0.0.0         UG    0      0        0
> ppp0
> 

Since David doesn't use his ethernet cards for anything except the private
network he might try the following:

(All with root privileges)
On both boxes:
  ifconfig eth0 down   

On box A:

  ifconfig eth0 192.168.1.1 netmask 255.255.255.0 up

On box B:

  ifconfig eth0 192.168.1.2 netmask 255.255.255.0 up

after that, depending on the version of his kernel, he might
need to do:
 
  route add -net 192.168.1.0 eth0

on both machines. After that he should be able to ping box A from
B and A from B.

[...]

> As additional information, use traceroute from one machine to the next,
> using the ethernet ip's. How is it trying to get from one machine to the
> other?

Good hint. Most ppp scripts will attempt to set the default gateway
to the ppp interface. Without an expicit route to the local network
packets might get sent into cyberspace ;-)

  Ralf