Could anyone help me with the Cisco IOS command for finding the suported protocols (level 2: link layer) by one serial interface, Serial 0/0 in this case?

The router is a Cisco 2600 (1 ethernet port, 2 serial ports).

Thanks in advance.

1 Answer 1


From an exec prompt,

Router#show protocols serial 0/0

would give you the protocols currently being used by the serial port numbered 0/0.

You can find out more in interface configuration mode:

Router#configure terminal
Router(config)#interface serial 0/0
Router(config-if)#encapsulation ?

When you hit the ? after typing 'encapsulation', it kicks into ios help which will provide a list of things your router would accept as a layer 2 encapsulation / protocol. Mine are wic-2t cards and offer sdlc, ppp, hdlc among others.

As an aside, to find out what protocols your actual router is geared up to work with, you can do

Router#show version

to find out your ios image (mine is currently 'c1841-adventerprisek9-mz.151-2.T.bin') and put it into the feature navigator at http://tools.cisco.com/ITDIT/CFN/jsp/SearchBySoftware.jsp

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