Connectivity Guide

● If all the ports in a port-channel have same port priority, the switch internally compares the interface names by base name,
module number, port number, and then selects the lowest one to be active. For example, Ethernet 1 is less than Ethernet 2
and hence Ethernet 1 becomes active.
● In a VLT network, if the interface name is the same on both the VLT peers, then the port in switch with lower system MAC
address becomes active.
Limitations
● OS10 switches cannot be a PXE client irrespective of whether it acts as a VLT peer or ToR switch.
● If you are configuring LACP fallback in a VLT domain, configure lacp fallback commands in both the VLT peers.
● If you do not enable LACP fallback in one of the VLT peers, or configure different time-out values in the peers, then the
switch might behave differently.
● The LACP fallback feature adds or groups a member port to the port channel only when the switch does not receive LACP
PDUs from the peer, to make the link connected to the PXE client device as operational. As PXE clients handle untagged
DHCP request, you need to configure the LACP fallback only on an untagged VLAN to reach the DHCP/PXE server.
● After the LACP fallback election, if a port with lower priority port is configured to be part of the same port-channel, it would
trigger re-election.
Configure LACP fallback
1. Enable LACP fallback with the lacp fallback enable command in port-channel INTERFACE mode.
2. Set a timer for receiving LACP PDUs using lacp fallback timeout timer-value in port-channel INTERFACE mode.
3. (Optional) Enable or disable LACP fallback port preemption using lacp fallback preemption {enable |
disable} in port-channel INTERFACE mode.
Example configuration
OS10# configure terminal
OS10(config)# interface port-channel 1
OS10(conf-if-po-1)# lacp fallback enable
OS10(conf-if-po-1)# lacp fallback timeout 20
OS10(conf-if-po-1)# lacp fallback preemption enable
View LACP fallback configuration
OS10# show port-channel summary
Flags: D - Down I - member up but inactive P - member up and active
U - Up (port-channel) F - Fallback enabled
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Group Port-Channel Type Protocol Member Ports
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1 port-channel1 (UF) Eth DYNAMIC 1/1/10(P) 1/1/11(I)
LACP fallback in non-VLT network
In a non-VLT network, LACP fallback enables rebooting of ToR or server connected to the switch through normal LACP. The
other end of the switch is connected to a DHCP/PXE server, as shown in the following illustration:
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Layer 2