Could it be due to my pc or university network? If it is in my pc is 
there a way to allow port 2401?
Many thanks.
Taylan
John Summerfield wrote:
> John Summerfield wrote:
>> Taylan Yetkin wrote:
>>> Both ping and traceroute  the host from fermi machines returns  
>>> success.  I need some time to understand the use of tcpdump.
>>> thanks,
>>> Taylan
>>
>> There's a fair chance there's a problematic firewall rule. Some 
>> examples that can confuse the issue.
>
> I can reach (ping) that host from here. Here's is what tcpdump shows 
> me when  I telnet to it:
>
> 08:35:27.548153 IP neutralino.physics.uiowa.edu > 
> dsl-58-6-192-22.wa.westnet.com.au: icmp 68: host 
> neutralino.physics.uiowa.edu unreachable - admin prohibited
>
> I interpret this as a firewall difficulty, the firewall is rejecting 
> the traffic with the excuse "icmp-admin-prohibited" which seems fairly 
> sensible.
>
> Same if I try port 25.
>
>
>
>>
>> smtp connexions from some locations to my gateway are forward using a 
>> DNAT rule to an internal system. If the internal system's down, a 
>> "host unreachable" response goes back, but ping and traceroute would 
>> work.
>>
>> When an unwelcome packet arrives at my gateway, I can choose to 
>> ignore it (DROP in iptables) or REJECT it. If I REJECT, I can add the 
>> excuse "icmp-host-unreachable."
>>
>>
>> A good start with tcpdump is something like this:
>>
>> tcpdump -i eth0 -s 8888 host cvs-server
>>
>> or use wireshark which has the same abilities and a GUI to guide the 
>> beginner.
>>
>>
>>
>>
>
>