So I’ve been watching the CCNP SWITCH videos in preparation for taking the exam again to renew my CCNP R&S and came across a couple problems in the Etherchannel Protocols video.
When going over PAgP, there was a matrix graphic to illustrate the compatibility between On, Off, Auto and Desirable. The first thing I noticed was that the matrix had a discrepancy between Auto and On. On one side (Auto/On) it said it would work, whereas the other axis (On/Auto) said it would not work. I think this was a simple typo since the value and result would be the same either way. But the bigger issue was when Ronnie was going over it and he said that Auto on one side and On (Manual Etherchannel) on the other side would work. I am 99% certain that this is incorrect.
For the same reason why Auto/Auto won’t work, PAgP is a protocol that requires communication between the two devices to negotiate the channel group. Having one side set to statically On would not meet this requirement, and is why Desirable, which sends PAgP packets in an ‘active’ fashion, is required. In saying that this Auto/On would work, he said that this is a difference between PAgP and LACP, but again I don’t believe this is the case and, just like LACP’s Active/Passive, having the other side set to On or Off would not allow the protocol to bring up the LAG. Both sides needs to be set to a PAgP or LACP protocol and at least one has to be active/desirable.
You may want to edit the matrix graphic and modify that part so that it gives the correct information in case it confuses someone.
I haven’t had a chance to test and confirm my belief (hence my 99% comment), but it immediately caught me off guard based on what my understanding was, and I did some research on it which confirmed my assumption.
Outside of that, everything else looked good :). Keep up the great work. Thanks!