set port channel xxx mode on tells the switch to go straight tho channeling, do not negotiate the channel with then neighbor. In catos there are two steps. Form the channel group then set its mode to desireable or on. The 2900 is probably trying to negotiate, try desireable on the 5500.
First do sho port capabil on the 550 and see how the ports can be grouped. Then try sh channel group and see if 4/23-24 are a channel group.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...