etherchannel trunk

[alan-wong]

Hi, my company using only one Cisco 3750 switch with VLAN1,2,3,4,5.

Now my company bought another cisco switch and we would like to etherchannel trunk between both and create new VLAN in new switch.  We look over from partner, some of them suggested we use LACP, and some of them suggest we use PAgP.  We are so confuse which will be better in our environment.

Previous: Router <> 3750 switch A (VLAN 1,2,3,4,5)
Now we bought another Cisco Switch B:  Router <>3750 switch A <> switch B (add more VLAN 6,7,8,9,10)
 

Which of below is the best choice to suit our company ? suppose we use 2 port of gigabitethernet 1/0/1 and 1/0/2 trunk?  All VLAN 1-10 need to communicate with each other.

!
interface GigabitEthernet1/0/1
 channel-group 1 mode active  <<< (use "active" or "desirable" is the best choice)
 switchport mode trunk
!
interface GigabitEthernet1/0/2
 channel-group 1 mode active
 switchport mode trunk
!
interface Port-channel 1
 switchport trunk encapsulation dot1q << (do we need put this? as we think this is by default after trunk?)
 switchport mode trunk
 switchport nonegotiate <<< (do we need "nonegotiate" if both switch setup same configure?)

[luckymike33 · Accepted solution]

Hi Alan,

Use 'active' - this means you are using LACP, which is a more modern choice than PaGP (Cisco proprietary).

You do not need the switchport trunk encap dot1q - as you rightly say, this is inherited by the etherchannel.

You do not need the switchport nonegotiate on the port-channel interface, this command is used to disable DTP, but s long as both ends (i.e. both switches' ports are configured with switchport mode trunk) you won't need this.

It can be tricky to bring up an etherchannel - just remember to shut down the member interfaces first, then apply the config, then 'no shut' all the interfaces, and the switch will sort everything out for you.

HTH