telnet

yuanguitao · ‎12-12-2013

Now one of my server, which runs linux, has the same subnet with my switch. for example 192.168.1.0/24. and the assume the ip of the server is 192.168.1.10, and the manage ip of switch is 192.168.1.100, but when I telnet 192.168.1.100 after I login on(use CRT via ssh protocol) the server,the connection between them seems lost temporarily. i have to wait for about 3 minutes before telnet sucess. and when i ping 192.168.1.100, i can't get any response during that period. do you know why?

cadet alain · ‎12-12-2013

Hi,

Can you sniff on the server while you try to communicate with the switch.

Regards

Alain

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yuanguitao · ‎12-12-2013

hello, can you show me how to sniff the server. bcz i don't know how to sniff the server via my pc when try to communicate with the switch. and here is the screenshot when i ping the switch via the server.

PS:I am sorry, i just erased the IP address of the server.

cadet alain · ‎12-12-2013

Hi,

Verify if you have tcpdump installed with "which tcpdump" command and if it is not then you'll to install it but I don't know this PiOS stuff so can't tell you how to do this (don't know the package management for this)

Once tcpdump is installed then "tcpdump -i "name of interface to sniff" -vv"

Regards

Alain

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yuanguitao · ‎12-12-2013

well, i can't find any cmd about tcpdump in the server, so i think the server never installed the application. but if i can sniff the switchport which connects to the server interface and get the data which come from the server interface. bcz that is easy to be done. what do you think of so.?

cadet alain · ‎12-12-2013

Hi,

Do you mean doing SPAN ? Yes it could be helpful too.

Regards

Alain

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yuanguitao · ‎12-12-2013

Yes, i just mean SPAN. and i get the data attached to the switchport. I found there are serval request message were sent out from server to switch and never get any repley message for a period when i do the ping. and when i try to telnet, tcp connection can't be established via three shaking-hands normally at beginning. and there are some tcp retransmission message were being sent at that moment. so can you make some inference?