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Re: can get DHCP IP address, but cannot ping


Andrew Lunn wrote:

On Fri, Jan 14, 2005 at 08:08:24PM +0900, xxchen wrote:


Hello, Nickolay



run "tcpdump icmp -n" and ping




Thank you very much. I ran "tcpdump icmp -n" 2 times and then get the following result.

(1)the first time:
------------------------------------------------
message of host:
----------------------------------------------
19:50:23.759123 192.168.0.198 > 192.168.0.59: icmp: echo request
19:50:23.759297 192.168.0.59 > 192.168.0.198: icmp: echo reply
19:50:31.201261 192.168.0.198 > 192.168.0.59: icmp: echo request
19:50:31.201319 192.168.0.59 > 192.168.0.198: icmp: echo reply
19:50:38.572536 192.168.0.198 > 192.168.0.59: icmp: echo request
19:50:38.572619 192.168.0.59 > 192.168.0.198: icmp: echo reply
19:50:45.890345 192.168.0.198 > 192.168.0.59: icmp: echo request
19:50:45.890428 192.168.0.59 > 192.168.0.198: icmp: echo reply
19:51:00.333976 192.168.0.198 > 192.168.0.59: icmp: echo request
19:51:00.334057 192.168.0.59 > 192.168.0.198: icmp: echo reply
19:51:14.777603 192.168.0.198 > 192.168.0.59: icmp: echo request
19:51:14.777691 192.168.0.59 > 192.168.0.198: icmp: echo reply
19:51:29.221228 192.168.0.198 > 192.168.0.59: icmp: echo request
19:51:43.664851 192.168.0.198 > 192.168.0.59: icmp: echo request
19:51:58.108477 192.168.0.198 > 192.168.0.59: icmp: echo request
19:52:12.552102 192.168.0.198 > 192.168.0.59: icmp: echo request

----------------------------------------------------------
while the target output following message:
------------------------------------------
PING - received 3 of 10 expected.


(2)the second time: ---------------------------------------------------- message of host: -------------------------------------------------- 19:54:37.019363 192.168.0.198 > 192.168.0.59: icmp: echo request 19:54:51.462989 192.168.0.198 > 192.168.0.59: icmp: echo request 19:55:05.906613 192.168.0.198 > 192.168.0.59: icmp: echo request 19:55:20.350239 192.168.0.198 > 192.168.0.59: icmp: echo request 19:55:34.793867 192.168.0.198 > 192.168.0.59: icmp: echo request 19:55:49.237488 192.168.0.198 > 192.168.0.59: icmp: echo request 19:56:03.681114 192.168.0.198 > 192.168.0.59: icmp: echo request 19:56:18.124738 192.168.0.198 > 192.168.0.59: icmp: echo request 19:56:32.568365 192.168.0.198 > 192.168.0.59: icmp: echo request 19:56:47.011988 192.168.0.198 > 192.168.0.59: icmp: echo request

-------------------------------------------------------
while the target output:
---------------------------------------------------
PING - received 0 of 10 expected.

the host has received request but why not send reply?
Looking forward to your further advice.



My guess would be the arp entry has timed out. You host might be arp'ing but the filter you used with tcpdump will not show it.

Andrew



tcpdump icmp or arp -n
try it


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