On Tue, Apr 13, 2004 at 09:46:21AM -0500, Kevin D. Kinsey, DaleCo, S.P. wrote:
> Can anyone help me interpret the following output? I read the ping
> manpage, but came to the end before I learned much that helps me
> here....
> <[EMAIL PROTECTED]> [/home/kdk] [16:25]
> #sudo ping -s 2048 app
> PING app.southuni.com (192.168.0.80): 2048 data bytes
> 36 bytes from app.southuni.com (192.168.0.80): Destination Host Unreachable
> Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
> 4 5 00 05dc 07bd 0 0000 3f 01 1677 192.168.0.2 192.168.0.80
The device (router?) is sending a host unreachable message which can be
for a variety of reasons, the most common being that there is no route
available to the destination. What address are you pinging from though?
You are trying to ping with a packet size of 2048 bytes (-s) but the MTU
of Ethernet is 1500 bytes.
You don't need to understand the information below to troubleshoot this
but here is an explanation anyway :) It's just a dump of the IP packet
headers that came back in the destination host unreachable message:
Vr 4 IP version 4
HL 5 Packet header length
TOS 0 Type of Service: Routine traffic
Len 05dc Packet length in hex (1500 bytes)
ID 07bd Identification - unique number to tell the ICMP packets apart
Flg 0 Flags - 3 bits: 0 (reserved), 0 (fragment if necessary), 0
(last fragment)
Off 0000 Fragment offset (not used since it is not a fragment)
TTL 3f Time to Live in hex (63 hops) - number of hops before packet
is discarded
Pro 01 IP protocol type (01 = ICMP, what ping uses)
Cks 1677 Packet header checksum
Src Source address that sent the "host unreachable" message
Dst Recipient of the "host unreachable" message - your machine
--
Stephen Fisher
San Jose, CA USA
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