[ale] SSH Cisco Networking Issue

[Omar Chanouha]

Thanks to everyone!

I found this article and sent it to the IT team: http://www.znep.com/~marcs/mtu/

Hopefully he will be able to understand and fix the issue now. And
yes, I too love this list!

Thanks again,

-O

On Sun, Sep 26, 2010 at 1:31 AM, Richard Bronosky <Richard at bronosky.com> wrote:
> So funny reading the responses that followed. When I heard that
> cat-ing a large file resulted in NO data as opposed to truncated
> data... I was confident that it was something like a packet size
> issue. I was not familiar with this MTU thing, but now I'm researching
> it out. I love this list. This is why I read it.
>
> On 9/16/10, Omar Chanouha <ofosho at gatech.edu> wrote:
>> Hello All,
>>
>>     Sorry for the long email, but I am having an issue with the IT guy
>> at my office, and this problem is out of my league. I set up a
>> LAMP/SSH server to host the intranet where I work. I am back at Tech
>> now, and need a way to connect to the server (Miami) to make changes.
>> I told the IT guy to open a port for me in the firewall so I can get
>> to the SSH server. Easy enough right?
>>
>> So, I can log into the server *.126, and I can send and recieve data
>> from it, HOWEVER if I try to receive large (> a paragraph) worth of
>> data the client hangs. The firewall still registers a connection, and
>> the client will just hang forever(ctrl-c does nothing, I have to close
>> the terminal). I would imagine this means it is waiting for data that
>> is not going to get there, and is also not receiving a disconnect
>> message.
>>
>> Example:
>>
>> o at remote:~$cat smallfile
>> Hello World!
>> o at remote:~$cat bigfile[no response]
>>
>> the same would apply to listing(ls) a small directory vs a large one.
>> Or even TAB completing a long list vs a short one.
>>
>> At address *.126 there are multiple machines, so when I connect to
>> *.126 I get port forwarded to another machine via NAT. Just as a test,
>> we made the relationship 1-1 at address *.124 (another ip we own) and
>> we made the firewall rule completely open at this address. The server
>> then worked. The IT guy then decided to make the rule more strict by
>> only allowing connection on port 22, and we went back to the previous
>> result. He then put in the Cisco SSH rule (rather than just opening
>> port 22) and it worked again.
>>
>> However, *.124 is not available for full time use, so we went back to
>> *.126 and applied the SSH rule, but got the same result as before.
>> Here is the weird part, when we port forward *.126 to one of the SSH
>> servers on one of the Cisco routers (rather than my machine) SSH works
>> fine. The IT guy thinks that the issue is coming from the NAT b/c we
>> are using the same firewall rule that worked w/ 1-1.
>>
>> Question, what could be causing the Ubuntu SSH server to hang ONLY
>> when larger amounts of data are being sent, but not affect the Cisco
>> SSH servers?
>>
>> Thanks,
>>
>> -O
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>
> --
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>
> .!# RichardBronosky #!.
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