[PLUG] Another network problem

[Zot O'Connor]

On Sun, 2003-12-21 at 16:33, Paul Heinlein wrote:
> On Sun, 21 Dec 2003, Rich Shepard wrote:
> 
> >   My notebook used to have no problems connecting to the Web -- or
> > pinging -- external hosts. Today I can ping internally but not
> > externally. When I try to use mozilla to reach google I see:
> > "connect: network not reachable".
> >

I assume you tried other sites?

Can you ping from the firewall out?

> >   ifconfig shows that eth0 is up. "route -n" shows, for eth0,
> > "192.168.55.0 0.0.0.0 255.255.255.0 U 0 0",
> 
> 1. On the notebook, run
> 
>      route -n | grep UG
> 

Specifically you should see something like this:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.55.1    0.0.0.0         UG    0      0        0 eth0

Dest of 0.0.0.0 with a genmask of 0.0.0.0 will match any packet (IP
ANDed with 0.0.0.0 is 0.0.0.0, thus the destination)

Gateway is where to send the matching patched which should be your
outbound router.



>    You should see the ip address of your gateway machine.
> 
> 2. On the gateway machine (is it a Linux box?), make sure that you're
>    forwarding packets:
> 
>      /sbin/sysctl net.ipv4.ip_forward
> 
>    It should contain a value of 1. If it's 0 (zero), then something's
>    wrong.

Not if it's doing NAT on some systems.  Depending on the kernel and kind
of natting/masquerading IP forwarding should be OFF (i.e. if the process
grabs the IP and resends it vs cross the tables).

Most people need this on.  But I doubt it changed.



> 
> Oh, I guess I should ask the prior question: can other hosts on your
> network successfully get to misc. sites on the wider Internet?
> 
> --Paul Heinlein <heinlein at madboa.com>
> 
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-- 
Zot O'Connor

http://www.ZotConsulting.com
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