Re: tcp/ip changes and how to work around them.

From: Tauno Voipio (tauno.voipio_at_iki.fi.NOSPAM.invalid)
Date: 03/13/04 

Date: Sat, 13 Mar 2004 20:18:31 GMT

Tim wrote:
> I work for a company that test products for various companies, one of
> the items we need to test is a circuit pack that includes an ethernet
> port. We want to be able to verify that the port works, ie., it
> responds to a ping. Since time is money, the pack (or packs, sometimes
> 5 or more will be tested) is simply plugged in and allowed to go
> through it's self test, then we ping it. We currently run this test
> using an old RedHat 4.1 box. We simply run arp -s IP MAC with an IP
> address that we use over and over, then ping that IP. It works
> fine,and looking at the network with Ethereal we see echo requests to
> the MAC and then echo replies from the MAC. The replies do have the IP
> set to 0.0.0.0 since the pack does not know the IP address, but it
> works and we can verify that the port will respond.
>
> We want to upgrade to a new "Ping Test" box running a more modern
> version of Linux so I've been trying this on RedHat 7.3 and it simply
> does not work. I can never get a reply from the card. Using Ethereal I
> see the echo requests, and from what I can tell they are the same as
> the echo requests from the old box, but I never get an echo reply. I'm
> not a network engineer and I simply don't understand why I'm not
> getting a reply when using the new box.
>
> Note: The card and the two Linux boxes are on a simple private network
> using a hub so that I can see all the network traffic with Ethereal.
> At all times I can see RARP "who is" requests from the card so I know
> it is on the network.
>
> Any idea why this will not work on a new version of Linux? Any idea
> how to get a reply?
>
> Thanks,
> Tim

Some of the newer Red Hats have a default firewall set up. Maybe
it's eating your packets.

Check with

    ipchains -nvL

or

    iptables -nvL

depending on the kernel version (ipchains for 2.2.x, iptables for
2.4.x).

HTH

Tauno Voipio
tauno voipio @ iki fi

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