[c-nsp] Telnet session dropped

[Roy]

On 12/26/2011 2:23 PM, Randy wrote:
> --- On Mon, 12/26/11, Roy<r.engehausen at gmail.com>  wrote:
>
>> From: Roy<r.engehausen at gmail.com>
>> Subject: [c-nsp] Telnet session dropped
>> To: "cisco-nsp at puck.nether.net"<cisco-nsp at puck.nether.net>
>> Date: Monday, December 26, 2011, 1:08 PM
>> I use RANCID ton a number of
>> routers.  About five days ago, it started failing on
>> three routers.  If I manually connect to these routers,
>> it seems to work for a minute or so and then the telnet
>> session gets disconnected.  The disconnect only occurs
>> during a data transfer such as "show conf"
>>
>> I tested it from several places so the telnet client
>> doesn't seem to be a factor.  The routers are all on
>> different ISPs and in different cities.  The only
>> common denominator between the failing routers is they are
>> all set to use a port other than 23.  This is done by
>> natting the external port to port 23 on a null interface.
>>
>> Rebooting the routers didn't help
>>
>> Any ideas?
>
> I wonder if your isps have decided to blackhole tcp traffic on port that you redirect to 23. A quick test to confirm would be to try without port redirection(terribly insecure) or use ssh. I have been bitten by XO..
> ./Randy
>

If they were blackholing traffic then I would think I couldn't even get 
connected in the first place