EtherChannel over 802.1Q Tunneling

In this lesson, we will take a look how you can create an Etherchannel link over 802.1Q tunneling. If you have no idea how 802.1Q tunneling works, it’s best to read my previous lesson first that covers the basics of 802.1Q tunneling.

Here’s the topology that I will use:

etherchannel over 8021q tunneling 4 switches

SW2 and SW3 are the service provider network. SW1 and SW4 belong to the customer and present two different sites. The idea is that we want to create an Etherchannel between SW1 and SW4 over the service provider network. First we will configure the trunk between SW2 and SW3:

SW2(config)#interface fastEthernet 0/21
SW2(config-if)#switchport trunk encapsulation dot1q 
SW2(config-if)#switchport mode trunk
SW3(config)#interface fastEthernet 0/21
SW3(config-if)#switchport trunk encapsulation dot1q 
SW3(config-if)#switchport mode trunk 

Our next move is to configure the interfaces pointing towards the customer switches. To “simulate” that our FastEthernet 0/23 +/24 interfaces on SW1 and SW4 are directly connected to each other we have to use a separate “transit” VLAN for each interface pair. Traffic on the FastEthernet 0/23 interface will flow in service provider VLAN 100 and traffic for FastEthernet 0/24 will use VLAN 200. Take a look at the picture below to visualize this:

etherchannel over 8021q tunneling dedicated path

If we would use a single transit VLAN for all traffic on the FastEthernet 0/23 and 24 interfaces then we run into issues with our Etherchannel because FastEthernet 0/23 could talk to 0/24 or vice versa.

Here’s the configuration for SW2:

SW2(config)#interface fastEthernet 0/23
SW2(config-if)#switchport access vlan 100
SW2(config-if)#switchport mode dot1q-tunnel 
SW2(config-if)#l2protocol-tunnel point-to-point pagp
SW2(config)#interface fastEthernet 0/24
SW2(config-if)#switchport access vlan 200
SW2(config-if)#switchport mode dot1q-tunnel 
SW2(config-if)#l2protocol-tunnel point-to-point pagp 

The magic bullet that makes the etherchannel possible is the l2protocol-tunnel command and specifying PAgP or LACP. The configuration for SW3 is similar:

SW3(config)#interface fastEthernet 1/0/23
SW3(config-if)#switchport access vlan 100
SW3(config-if)#switchport mode dot1q-tunnel 
SW3(config-if)#l2protocol-tunnel point-to-point pagp
SW3(config)#interface fastEthernet 0/24
SW3(config-if)#switchport access vlan 200
SW3(config-if)#switchport mode dot1q-tunnel
SW3(config-if)#l2protocol-tunnel point-to-point pagp

Our service provider switches are now ready, the configuration on the customer switches is just a regular Etherchannel configuration:

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Forum Replies

  1. Hi Rene,

    Now the Etherchannel is formed across the Switch 1 and Switch 4, is it the trunk link, suppose i have Vlan 10,20,30,40 on Switch 1, so once etherchannel is formed, all this Vlan will pass through it?? without any extra configuration on Service provider Network??

    Does this link also send VTP message?? can we also make Switch 1 as Vtp server and Switch 4 as VTP client, and after that If we create New Vlan on switch 1 for example Vlan50, will this Vlan will pass over Etherchannel to Switch 4 since switch 4 is VTP client.

  2. Hi Rene,
    I recently viewed Q in Q tunneling for Etherchannel, and i have below query, please advise.

    Now the Etherchannel is formed across the Switch 1 and Switch 4, is it the trunk link, suppose i have Vlan 10,20,30,40 on Switch 1, so once etherchannel is formed, all this Vlan will pass through it?? without any extra configuration on Service provider Network??

    Does this link also send VTP message?? can we also make Switch 1 as Vtp server and Switch 4 as VTP client, and after that If we create New Vlan on switch 1 for example Vlan50, will this Vlan will pass ov

    ... Continue reading in our forum

  3. Hi Rupesh,

    Once the Etherchannel is formed, all VLAN traffic from SW1 and SW4 should pass yes. We are using Q-in-Q tunneling so it should work.

    You can make VTP work by adding l2protocol-tunnel vtp. You can also do this for CDP and STP.

    Rene

  4. Hello Frederic

    It seems that when you configure Etherchannel on the link between the service provider equipment and the customer equipment, you can only configure each link to carry a single VLAN. This means that you will require the same number of physical links as VLANs that you want to share across the QinQ tunnel. Etherchannel will not provide redundancy for other VLANs if a physical link fails in this scenario. This is further supported by this Cisco documentation that describes how to configure this:

    https://www.cisco.com/c/en/us/td/docs/switches/lan/c

    ... Continue reading in our forum

  5. Hi Lazaros,
    Glad to read that I discovered a bug !!!
    Yes it made me practice and to be definitely certain of what was going on, I labbed it this morning with real devices (2 switches (catalyst 3750) and 2 pcs) and played a bit around load balancing, stp cost, interface packets rates and so on.
    Pity to see that my GNS3 environment is buggy but now, indeed I know how things work.
    Thank you for your time and help

    Regards
    Fred
    Ebverything is working as expected

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