"Bob Puff@NLE" <[EMAIL PROTECTED]> wrote:
> Hi Gang,
>
> Here's a weird problem I'm trying to work through.
>
> Mandrake 7.1 machine has two network cards:
> Card A on 1.2.3.4, with default gateway set to 1.2.3.1.
> Card B on 20.0.0.20.
> Both networks connect to the outside world.
>
> Problem: I can successfully ping the 1.2.3.4 address, but I cannot
> ping the 20.0.0.20 address. The ping packet gets to the machine ok,
> (on card B) but the machine is sending the reply packet thru the
> 1.2.3.4 network!
>
> I have another machine similarly configured, and it works fine.
> Also note that from another machine also on the shared networks, I CAN
> ping the 20.0.0.20 address, but I can see the reply is still coming back
> through card A (1.2.3.4). So at least I know my ping isn't disabled.
That reminds me of an amusing story I'll tell later.
Anyway, what's the output of 'route' (or 'route -n' may be better) on those
2 different machines?
(And for finding out how packets GET there, use traceroute, but
unfortunately it does not tell you how they get BACK! Here's my
story: )
I had my laptop set up on a network and was logged in remotely.
I was working on getting dialing in to my new ISP to work, and
had finally managed to get chat and all to go. So here's a small
picture of what I had:
<me> <workstation>----<eth_card><laptop><modem>----<isp>---<internet>
|
|----------<router>----<gateway>---<etc>---<internet>
So, you see, I had 2 ways to hit the internet from my laptop - through
my isp and through my local LAN. One thing I'd noticed is that ppp no
longer seems to want to overwrite my default route (perhaps I missed an
option, but thats ok I didn't really want it to during my testing).
So, from the workstation I typed "traceroute <ip_address_of_modem_on_laptop>"
The OUTGOING packet went:
workstation
router
gateway
etc
internet
...
isp
modem_on_laptop
but, being the inquisitive type, I wondered if the RETURN reply was going
where I thought it would (directly back), so I started up kpppload. I
could see the INCOMING ping or traceroute packets being registered on
the laptop modem, BUT NOT THE REPLIES. (so it was doing what I expected)
"Huh?" you say? Well, my LAPTOP had a default route as well as an
interface ON THAT network segment, so the routing code said, 'heck,
I'll just reply to the direct network segment, its shorter'.
We had a good laugh around here about 'the worlds longest ground loop' ;-)
rc
Rusty Carruth Email: [EMAIL PROTECTED] or [EMAIL PROTECTED]
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