lacp port-priority [value]
Sets the LACP port priority for an interface, which determines which ports become active in an LACP EtherChannel when the maximum number of allowed ports is reached.
lacp port-priority [value]When to Use This Command
- Controlling which ports are active in a 4-port EtherChannel when only 2 ports are allowed, ensuring critical links stay active.
- Prioritizing high-bandwidth or redundant links over lower-speed or less reliable links in a multi-switch LACP bundle.
- Ensuring specific ports (e.g., uplinks to core) are preferred over access ports in a mixed EtherChannel.
- Troubleshooting LACP negotiation by adjusting priority to force a specific port to become active.
Command Examples
Setting LACP port priority to 100 on an interface
interface GigabitEthernet0/1
lacp port-priority 100Switch(config-if)# lacp port-priority 100
Switch(config-if)# end
Switch# show lacp neighbor
Flags: S - Device is requesting Slow LACPDUs
F - Device is requesting Fast LACPDUs
A - Device is in Active mode P - Device is in Passive mode
Channel group 1 neighbors
Partner's information:
LACP port Admin Oper Port Port
Port Flags Priority Key Key Number State
Gi0/1 SA 100 0x1 0x1 0x101 0x3D
Gi0/2 SA 32768 0x1 0x1 0x102 0x3DThe 'lacp port-priority 100' command sets the priority to 100 (lower is better). In the 'show lacp neighbor' output, the 'LACP port Priority' column shows 100 for Gi0/1, indicating it has higher priority than the default 32768 on Gi0/2.
Verifying LACP port priority after configuration
show etherchannel 1 port-channelPort-channel: Po1 ------------- Age of the Port-channel = 00d:00h:05m:32s Logical slot/port = 1/1 Number of ports = 2 HotStandby port = null Passive port list = null Port state = Port-channel Ag-Inuse Protocol: LACP Ports: 2 Max = 2 Ports in the Port-channel: Index Load Port EC state No of bits ------+------+------+------------------+----------- 0 00 Gi0/1 Active 0 1 00 Gi0/2 Active 0 Time since last port bundled: 00d:00h:05m:30s Gi0/1 Time since last port Un-bundled: 00d:00h:00m:00s Never
The output shows the EtherChannel summary. Both ports are Active. If the maximum number of ports were set to 1, the port with lower LACP priority (Gi0/1) would remain active, and the other would become HotStandby.
Understanding the Output
The 'lacp port-priority' command itself does not produce output; it configures the interface. To verify the effect, use 'show lacp neighbor' or 'show etherchannel summary'. In 'show lacp neighbor', the 'LACP port Priority' column displays the configured priority (lower value = higher priority). In 'show etherchannel summary', the 'EC state' column shows 'Active' for bundled ports; if a port is not bundled due to priority, it may show 'Hot-Stby' or 'Suspended'. A good configuration ensures critical ports have lower priority values (e.g., 100) than others (default 32768). Watch for ports that are unexpectedly not bundled; check their LACP priority and system priority.
CCNA Exam Tips
CCNA exam tip: LACP port priority is used to determine which ports become active when the maximum number of ports is reached; lower value = higher priority.
CCNA exam tip: The default LACP port priority is 32768; you can set it from 1 to 65535.
CCNA exam tip: LACP port priority is per-interface, while LACP system priority is global; both affect port selection.
CCNA exam tip: In the exam, you may be asked to configure LACP so that a specific port is preferred; use 'lacp port-priority' with a low value.
Common Mistakes
Mistake: Setting the priority too high (e.g., 65535) thinking it gives preference; actually lower is better.
Mistake: Forgetting to set the LACP system priority as well; port priority only matters if system priority is equal.
Mistake: Applying the command to the wrong interface or not verifying with 'show lacp neighbor'.
Related Commands
channel-group [id] mode [mode]
Assigns an interface to an EtherChannel bundle with a specified channel-group number and mode (active, passive, or desirable) to aggregate multiple physical links into a single logical link for redundancy and increased bandwidth.
lacp system-priority [value]
Sets the LACP system priority to determine which switch controls the EtherChannel bundle when negotiating with a peer.
show etherchannel summary
Displays the status and configuration of all EtherChannel interfaces on the switch, used to verify channel bundling, port membership, and protocol state.
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