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-   -   2 NIC problem, no internal ping, only external (http://www.linuxquestions.org/questions/linux-networking-3/2-nic-problem-no-internal-ping-only-external-36973/)

browny_amiga 12-01-2002 11:17 AM

2 NIC problem, no internal ping, only external
 
Hi

I have this tough cookie here which is in the process to drive me crazy:

Out of the box Redhat 6.2 running on 100MHZ Pentium, 2 NICs installed,
PCNET32 (10.10.10.11) + RTLxxxx (10.10.10.10) (Realtek something).
This setup is a trial for an internal net / internet setup.

The Problem: When on the box, I cannot ping any of these two cards, which first indicated to me that they don't work properly. Funny thing is that from external boxes I can ping all right on both IPs and ifconfig shows them (eth0 eth1 lo) properly up.
The module config should be alright since I wrestled with this a lot and also read several FAQs for the 2 NIC scenario.
The funny thing is that although I cannot ping localy, I use a client/server application that can connect to 10.10.10.10 no problems, data exchange works both ways (looks like there is a bi directional problem?)
No firewall is on currently, so nothing is blocked.

I am a little lost here, since I know that ping is one of the basic things that need to work, so I am amazed that I can use that NIC for datatransfer but not ping it localy.

Is there some kind of diagnosis that I can run to find out what is foul? Could the motherboard (pci) be damaged? Before, when I only had 1 NIC, it worked perfect!


Any pointers appreciated
(from a not-so-much newbie-anymore that is stuck ;-)

Markus

clavius 12-01-2002 11:24 AM

Re: 2 NIC problem, no internal ping, only external
 
Quote:

Originally posted by browny_amiga
[B]Hi

Out of the box Redhat 6.2 running on 100MHZ Pentium, 2 NICs installed,
PCNET32 (10.10.10.11) + RTLxxxx (10.10.10.10) (Realtek something).
This setup is a trial for an internal net / internet setup.

The Problem: When on the box, I cannot ping any of these two cards, which first indicated to me that they don't work properly.
Your problem is that you have IPs from the SAME subnet on 2 different NICS. So your cards are Ok, but change one's IP to another one, on other subnet.

Seach with google about networking tutorials on routing and you'll see why ;)

browny_amiga 12-01-2002 06:39 PM

Thanks for the pointer. Although I know quite some things about TCP/IP, that routing stuff and subnets was always (is still ;-) somethign that evades me.

I will look into it. Do you know any URL where they specifically talk about WHY it does not work?
I was always thinking that the 2 NICs would communicate perfectly, since they are almost ...connected... to eachother..

Anyway, thanks for the help. Routing is my next study subject !

Thanks again

Markus

clavius 12-02-2002 01:21 AM

Quote:

Originally posted by browny_amiga
I will look into it. Do you know any URL where they specifically talk about WHY it does not work?
I was always thinking that the 2 NICs would communicate perfectly, since they are almost ...connected... to eachother..
They communicate PERFECTLY, but think about it:
You type "route -n" and....
You have TWO routes:
10.10.10.0 255.255.255.0 eth0
10.10.10.0 255.255.255.0 eth1

If you generate a packet, WHERE did the router (Linux, Cisco, Windows NTs) know WHERE to send it ? On eth0 OR eth1 ?


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