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Community Member

NBAR with skype?


Ive read elsewhere in these forums that it is possible to use the NBAR features in IOS to block/manage Skype traffic. Im particularly interested in whether or not this will permit skype voice but be able to block skype video.

I have a 1811 router with the following output from a show version:

Cisco IOS Software, C181X Software (C181X-ADVENTERPRISEK9-M), Version 12.4(2)T2, RELEASE SOFTWARE (fc3)

First my key questions are:

What is the meaning of 'T2' in this version versus the 'T' which seems pretty well-documented on software relases page?

From what I understand the skype protocol is embedded in NBAR as of IOS version 12.4(4). Does this mean that the IOS version currently running on my 1811 cannot use NBAR to classsify skype traffic?

Will the 1811 support an IOS upgrade to the necessary verson to classify skype?

Will the software upgrade be free?




Re: NBAR with skype?

You dont need to upgrade you can use PDLM for skype

try this web site

More info about PDLM you can fid here:

Hope this helps

Community Member

Re: NBAR with skype?


Thanks for the reply.

From looking elsewhere on these forums, It would appear to me that there is no pdlm for skype?


Specifically, it quotes a document as follows:

"Skype Classification via NBAR Packet Description Language Modules Skype is a popular VoIP telephony service that allows users to speak, send instant messages, and/or send files to one another via the Internet. This functionality provides the ability to recognize Skype application traffic in Cisco IOS Software. The NBAR PDLM for Skype classification is

integrated into Cisco IOS Software. There will not be a downloadable PDLM for Skype because of infrastructure changes required to accommodate Skype application classification."

But what you are telling me is that there is a way. I am interested to hear more. I also submitted a request to TAC on this same issue. Their response was that yes the skype pdlm is not available separately from IOS but that it is embedded in NBAR in IOS release 12.4(4).

They also told me that the only router supported in the 1800 series is the 1841. Thats a bummer for me, since I have the 1811.

What is the best way forward here?



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