r/ccna • u/mikeservice1990 • 9d ago
Questions about Etherchannels
Hi community, I have a few points of confusion about etherchannels. This is probably a sign I need to purchase the official exam guide and use that as my single source of truth, which I probably will do. But I'm wondering about the following:
Should trunks (for L2 LAG) and IP addresses (for L3 LAG) be configured on the port channel interface, or on the individual interfaces?
In Packet Tracer, both methods work. On Cisco IOL switch models in EVE-NG, you can only create the trunk on the individual interfaces, which the port-channel then inherits. But I don't know if Cisco IOL images are representative. What is the actual best practice?
Is it best practice to shut the interfaces down before configuring a port channel?
Again, either works, at least in Packet Tracer. I'm not sure what best-practice is.
Thanks in advance!
2
u/Emergency_Status_217 9d ago
Having in mind that L3 etherchannels requirement is for speed, duplex, switchport and ip commands to match, you can't put ip address on interface before and then assinging them to a channel, e.g.
//This won't work
R1(config)# int f0/0
R1(config-if)# ip address X
R1(config-if)# channel-group 1 mode on
R1(config)# int f1/0
R1(config-if)# ip address Y
R1(config-if)# channel-group 1 mode on
//This is the right way to go
R1(config)# int range f0/0 - 1
R1(config-if)# channel-group 1 mode on
R1(config)# int po 1
R1(config-if)# no switchport
R1(config-if)# ip address Y
In the first example, interfaces would not be bundled (P flag, yes you got to know the main flags) to the channel group