NIC sends but can't receive?!?!?!

NIC sends but can't receive?!?!?!

Post by Ted » Wed, 29 Nov 2000 11:40:27



I have an ethernet card that can send arp and icmp messages but it
won't read the responses. I can see the messages and the responses
on the network using tcpdump on another computer, which has the same
version of Linux and the same model NIC.

I installed/configured the NIC on the non-working computer AFTER
installing Linux, but the NIC was already in the working one BEFORE
I installed Linux on that one, so the installation program must
have correctly configured its NIC and its driver module.

There must be something else I have to enable or configure on the
non-working one to get it to read the messages...is there???

I know the non-working card really works because I've tried it works
in the working computer and the working one stopped working in the
non-working computer--so it must be my configuration.

The Linux is Red Hat 6.2 and the NICs are 3com 3c509b-TP

Thanks a lot.

Ted Bogart
Raleigh, NC

 
 
 

NIC sends but can't receive?!?!?!

Post by Tony Jeffri » Fri, 01 Dec 2000 14:14:05



>I have an ethernet card that can send arp and icmp messages but it
>won't read the responses. I can see the messages and the responses
>on the network using tcpdump on another computer, which has the same
>version of Linux and the same model NIC.

<snip!>

I know this may sound dumb, but have you checked the cable and the port on
your hub and/or switch? It's a long shot, but it seems to me that
perhaps one of the pairs in your ethernet connection may have gone awry
somewhere. If you're having problems with other protocols as well, then
I would definitely check this out. If other protocols are working, then
I'm stumped. I don't know of any parameters in the kernel configuration
or elsewhere that could make a box transmit-only.

Of course, I'm not a network admin, and I could be entirely wrong. I have,
however, heard of admins connecting their sniffers to their networks with
only one pair of the CAT5 cable working so that the box could listen on
the network with zero chance of any acknowledgements of any kind getting
back to the network (such as from someone using a ping sweep to map the
network). I suppose the same thing could happen, but in reverse...

--

The health of a democratic society may be measured by the quality
of functions performed by private citizens.  -- Alexis de Tocqueville

 
 
 

1. TCP send/receive queue in 'netstat -a'

What is the unit of measurement for TCP send
and receive queue in 'netstat -a'?

EXAMPLE:
TCP
   Local Address        Remote Address    Swind Send-Q Rwind Recv-Q  State
   -------------------- -------------------- ----- ------ ----- ------ -------
   localhost.32776      localhost.32774      32768      0 32768      0 ESTABLISHED
   localhost.32774      localhost.32776      32768      0 32768      0 ESTABLISHED

What does Send-Q and Recv-Q measuer?
Number of bytes, packets, or connections?

Thanks!

Lance Spitzner
http://www.enteract.com/~lspitz
Internetworking & Security Engineer
Dimension Enterprises Inc

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