A Layer 3 EtherChannel combines routed ports into one logical link that forwards packets at the network layer. On a multilayer switch, it provides simple load balancing across multiple physical links while keeping IP addressing and routing on one logical interface. section 16.4
Unlike Layer 2 EtherChannel, routed ports do not create Layer 2 loops and are not disabled by STP. The main benefits are packet load balancing and easier management than configuring several independent Layer 3 links. section 16.4
Build the logical routed link in this order:
- Select the physical member ports and use no switchport to convert them into routed ports. section 16.4
- Assign the ports to the same channel group, using LACP active or passive, PAgP desirable or auto, or static on mode. section 16.2.1 section 16.2.2
- Configure the IP address on the port-channel interface, not on an individual member port. section 16.4
- Use show etherchannel summary to verify the result; the R flag identifies a Layer 3 EtherChannel, while P identifies bundled member ports. section 16.4
LACP Layer 3 EtherChannel on SW3
SW3(config)# interface range g0/2-3 SW3(config-if-range)# no switchport SW3(config-if-range)# channel-group 2 mode active SW3(config-if-range)# interface po2 SW3(config-if)# ip address 192.168.1.1 255.255.255.252 The first command sequence makes G0/2 and G0/3 routed ports, adds them to LACP channel group 2, creates Po2, and places the IP address on that logical interface. A working peer uses a compatible Layer 3 EtherChannel configuration. section 16.4
Layer 3 EtherChannel can use PAgP, LACP, or static on mode, but dynamic negotiation checks neighboring configuration before forming the channel. LACP is the standard choice when interoperability with another vendor matters. section 16.2.1 section 16.2.2
