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Cisco router - check for open ports

Posted on 2011-09-13
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Last Modified: 2012-05-12
Hi There,

We currently have a Cisco 1841 router and it only accessible via telnet and we are in the process of upgrading this router and was wanting to know if anyone was able to tell me the entire command line commands to run on this router in order to find all currently open ports?


Thanks in advance
Adrian
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Question by:Adma1
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by:Ernie Beek
ID: 36528826
Well you should be able to see that in the config. So use show run or show start. All ports not explicitly defined in the access lists should be closed.
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by:SuperTaco
SuperTaco earned 166 total points
ID: 36528831
I third party tool is an easier bet for you try using NMAP (ZenMap GUI) it will give you a readout of all open ports on your network.

http://nmap.org/zenmap/
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by:Ernie Beek
ID: 36528844
You can always double check by using something like shields up : https://www.grc.com/x/ne.dll?bh0bkyd2
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Istvan Kalmar earned 167 total points
ID: 36529019
server#sh ip sockets


Proto    Remote      Port      Local       Port  In Out Stat TTY OutputIF
 17 192.168.212.1     514 10.150.0.3      53786   0   0 100010   0
 17   --listen--          10.150.0.3       1975   0   0   11   0
 17 0.0.0.0             0 10.150.0.3       2228   0   0  211   0
 17 10.155.12.44       68 10.150.0.3         67   0   0 2211   0
 17 10.155.0.110    61731 10.155.0.1        161   0   0    1   0
 17   --listen--          10.150.0.3        162   0   0   11   0
 17   --listen--          10.150.0.3      57131   0   0    1   0
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by:Ernie Beek
ID: 36529812
@ikalmar: it that just like a netstat -an ?
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by:SuperTaco
ID: 36529819
yes, very similar.  I didn't recommend it, because i usually like using scanning tools.  either way will work though.
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Expert Comment

by:Ernie Beek
ID: 36529856
Cool, didn't know that one. Had my learning experience for today :)
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Author Comment

by:Adma1
ID: 36533577
Thanks everyone for your responses,

Ikalmar: when I run the sh ip sockets command I receive the following error

'xxxx'-GW0#sh ip sockets
                     ^
% Invalid input detected at '^' marker.

is there a series of commands that I need to run prior to the sh ip sockets command?

Thanks,
Adrian
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by:tirabytes
tirabytes earned 167 total points
ID: 37091240
Try: sh control-plane host open-ports

Or you can do it by checking both inbound nat and accesslist on your internet facing interface (if there is any).

sh conf | inc ip nat inside
or
sh ip nat trans

&

sh access-list



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