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PINGing an embedded system

I'm PINGing an embedded system from XP over a SLIP encoded serial link. Below are example outward and inbound packets that have been sent to and received from my embedded system. As far as I can make out the response is good but the PING always tells me it's timed out. I'm probably missing something obvious here. If anyone who knows about IP can tell me what the problem is I'd be grateful.

Thanks.

Rog.

Request IP/ICMP packet:

C0

45 00 00 3C C4 8C 00 00 80 01 60 30 0A 01 01 01 0A 01 01 02 08 00 49 5C 03 00 01 00 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 72 73 74 75 76 77 61 62 63 64 65 66 67 68 69 C0

Reply IP/ICMP packet:

C0

45 00 00 3C C4 8C 00 00 80 01 60 30 0A 01 01 02 0A 01 01 01 00 00 FB FF 03 00 01 00 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 72 73 74 75 76 77 61 62 63 64 65 66 67 68 69 C0
Reply to
Roger
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^^^^^ 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:

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Reply to
Patrick Klos

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

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Cheers, Alf

Reply to
Unbeliever

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.

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Reply to
George Wicks

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.

Reply to
Roger

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

Reply to
Ed Beroset

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