Layer 3 Etherchannel on Cisco IOS Switch

Hi Santhosh,

In this example you’ll have L2 interfaces from the access switch to the distribution switch with SVI interfaces for L3 so yes, you’ll have L2/L3 traffic over the same link. It works but it’s not what we normally do.

With a design like this where we use trunks from the access layer to the distribution layer we normally don’t use SVI interfaces on the access layer. You can stick to cheaper L2 switches for the access layer and let the distribution layer do the routing…that’s where you configure SVI interfaces.

Let me give you two examples for a typical L2 or L3 design.

L2 design:

hostname ASW1
!
interface GigabitEthernet0/1
 description HOST_VLAN10
 switchport access vlan 10
 switchport mode access
 negotiation auto
!
interface GigabitEthernet0/1
 description TRUNK_TO_DSW1
 switchport trunk allowed vlan 10
 switchport trunk encapsulation dot1q
 switchport mode trunk
hostname DSW1
!
interface GigabitEthernet0/1
 description TRUNK_TO_ASW1
 switchport trunk allowed vlan 10
 switchport trunk encapsulation dot1q
 switchport mode trunk
!
interface Vlan10
 ip address 192.168.1.254 255.255.255.0

The design above has L2 on the access layer and L2/L3 on the distribution layer. Here’s a “pure” L3 design, even on the access-layer:

L3 design:

hostname ASW1
!
interface GigabitEthernet0/1
 description ACCESS_VLAN_10
 switchport access vlan 10
 switchport mode access
!
interface GigabitEthernet0/2
 description UPLINK_TO_DSW1
 no switchport
 ip address 10.10.10.1 255.255.255.252
!
interface Vlan10
 description GATEWAY_VLAN10
 ip address 192.168.1.254 255.255.255.0
hostname DSW1
!
interface GigabitEthernet0/2
 description LINK_TO_ASW1
 no switchport
 ip address 10.10.10.2 255.255.255.252

In the design above, VLANs are restricted to the access layer switch. The link to the distribution layer is L3. The advantage of this is that you don’t have to deal with STP anymore.

Hope this helps!

Rene