Trunking with Ether Channel

[Wajih Rehman]

Hello,

I have two switches with 4 links connecting together. I could see all the links are trunking and STP block the redundant path. Then I setup ether channel between them.

From Switch-2:

IOU2#show etherchannel summary 
Flags:  D - down        P - bundled in port-channel
        ......................
        ......................
Number of channel-groups in use: 2
Number of aggregators:           2

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
21     Po21(SU)        PAgP      Et0/0(P)    Et0/1(P)    Et0/2(P)    
                                 Et0/3(P)  

From Switch-1:

IOU1#show etherchannel summary 
Flags:  D - down        P - bundled in port-channel
        ......................
        ......................
        
Number of channel-groups in use: 2
Number of aggregators:           2

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
12     Po12(SU)        PAgP      Et0/0(P)    Et0/1(P)    Et0/2(P)    
                                 Et0/3(P)    

What I was expecting that when I will display interfaces with trunk , I should see these two in their switches. However, the output does not show them.

From Switch-1:

IOU1#show int trunk 
IOU1#
IOU1#

From Switch-2:

IOU2#show interfaces trunk 

Port        Mode             Encapsulation  Status        Native vlan
Et3/2       desirable        n-802.1q       trunking      1
Et3/3       desirable        n-802.1q       trunking      1

Port        Vlans allowed on trunk
Et3/2       1-4094
Et3/3       1-4094

Port        Vlans allowed and active in management domain
Et3/2       1,10-11
Et3/3       1,10-11

Port        Vlans in spanning tree forwarding state and not pruned
Et3/2       10-11
Et3/3       11
IOU2#

Is there anything else I need to do?    Thanks for your help

Wajih

[Madhukrishnan Gopinathan Nair]

Did you configure the port-channel interfaces as "switchport mode trunk"

Thanks,

Madhu

[Wajih Rehman]

Thanks Madhu and Inyatullah. The problem was missing switchport mode trunk command in the interface.

One more question, do we need to define trunk on port-channel as well or interface is enough?

[Madhukrishnan Gopinathan Nair]

The best practice for port-channeling is you add member ports to port-channel by the channel-group command and all other configuration should go under port-channel. 

So basically when you say under port-channel "switchport mode trunk", it goes to member ports automatically.

Thanks,

Madhu

[InayathUlla Sharieff]

Just like to add what Madhu said,,,

Always do the configuration on the port channel and not on the physical interfaces.... As u know that the physical interfaces part of port channel will inherit the configuration. Were as if u do the configuration on the interface the same will not be copied back to port channel.

Hth

Regards

Inayath

[InayathUlla Sharieff · Accepted solution]

By default DTP is disabled on most of the switches.

Either enable the DTP or confiugre the port to be in the trunk.

int x/x

switchport mode desirable  or

switchport mode trunk

HTH