PINGing an embedded system

^^^^^ ICMP checksum

You seem to have computed the ICMP checksum as 0xfbff. I'm pretty sure the ICMP checksum should be 0x515c.

========= For LAN/WAN Protocol Analysis, check out PacketView Pro! ========= Patrick Klos Email: snipped-for-privacy@klos.com Klos Technologies, Inc. Web:

Grab a copy of ethereal network analyser (it's free), will show you all the components of request and response including checksums and whether or not they're correct. See

Cheers, Alf

snipped-for-privacy@osmium.mv.net (Patrick Klos) wrote in news:cueajn$g90$ snipped-for-privacy@pyrite.mv.net:

Roger, You might want to take a look at RFC 1701, "Computing the Internet Checksum" - it talks about computing the checksum for IP, ICMP, IGMP, UDP, and TCP. I had a checksum bug once in an implementation of IGMP, so it does happen.

....

Thanks for your comments. I'll sort out the CS problem. It's typical that I've been looking at this for ages but miss the obvious problem!

Ethereal is a good idea but unfortunately it doesn't capture data from SLIP serial links.

Rog.

I have found that using tcpdump on a Linux box is invaluable in troubleshooting such connections. Don't let the name fool you -- it's particularly good with low level stuff like PPP negotiations. You might find it worthwhile to keep a Knoppix CD around (bootable Linux) just for that purpose if it doesn't suit you to actually install the OS on one of your computers.

Ed