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etherchannel trunk with two cisco switch

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 command 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?)


Everyone's tags (2)
VIP Mentor

HelloMy understanding is pagp


My understanding is pagp and lacp basically perform the same features - however as PAGP is cisco propriety LACP is IEEE standard which can be used between different route/switch vendor platforms.


As for disabling DTP ( switchport nonegotiate) - i would agree to do this suggestion, As so not to  have trunks being dynamically created.

Lastly i would manually prune unused vlans across trunk interfaces, to save on cpu and memory usage because of the stp instances that coild be used ( however such a small vlan database  like yours would not be an issue)


So to summarise:

Cisco to Cisco ehterchannels =PAGP
Cisco to other vendors = LACP


L2 etherchannel
1) default physical interfaces (if possible)
2) configure port-channel in physical interfaces
-- port-channel will be created automatically

3)create trunking encapsulation or access port mode directly in port-channel interface
4)enable physical interfaces "no shut"

conf t
default int ran fa0/1 -3 ( if applicable)

int ran fa0/1 -3
shut ( if applicable)
channel-group 1 mode xxx

int port-channel 1
switchport trunk encap dot1q
switchport- mode trunk
switchport nonegotiate
switchport trunk allowed vlan 1-10




kind regards

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VIP Expert

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I would recommend LACP over PAgP (as Paul notes, its not proprietary).

BTW, on 3750s, if you're going to Etherchannel, you might want to review whether the default load balancing algorithm should be changed.  (src-dsc-ip is often a good choice.)