SNMP 161, 162, 1993 TCP or UDP

Unanswered Question
Feb 18th, 2002

As we know, port 161/162/1993 could be TCP or UDP and snmp traps are sent out in UDP. Could you please tell me when TCP 161/162/1993 will be used and how to identify it is TCP or UDP on a Cisco router? Thanks very much!

I have this problem too.
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nhabib Wed, 02/20/2002 - 05:31

As of version 11.x of IOS, Cisco no longer uses

port 1993. If you are on a version of IOS that

is below 11.x, you are not Y2K compliant.

By default, SNMP uses UDP, not TCP. Polling

(sent by servers) goes to port 161. Traps (sent

by agents) go to port 162.

velimirmkd Wed, 02/20/2002 - 05:41

As I know UDP 161/162 are used for SNMP. On my network a monitor only these two ports concerning the SNMP. If you want to verify if it is udp or tcp you can do it very easily with an access list. For example:

access-list 166 permit icmp any any echo

access-list 166 permit icmp any any echo-reply

access-list 166 permit udp any any log

access-list 166 permit tcp x.x.x.x x.x.x.x any log

access-list 166 permit tcp any x.x.x.x x.x.x.x log

access-list 166 permit ip any x.x.x.x x.x.x.x

access-list 166 permit ip any any

You can even simplyfy this list by using any any for the tcp and fot the ip part.

This way you won't affect your regular communication and you'll be able to view the log messages on the console or terminal.

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Posted February 18, 2002 at 4:32 PM
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