lacp system-priority [value]
Sets the LACP system priority to determine which switch controls the EtherChannel bundle when negotiating with a peer.
lacp system-priority [value]When to Use This Command
- Ensuring a specific switch becomes the LACP active partner in a multi-vendor environment
- Load balancing across multiple EtherChannels by adjusting priority per switch
- Troubleshooting LACP negotiation failures due to priority mismatch
- Standardizing priority across all switches in a data center for predictable behavior
Command Examples
Setting LACP system priority to 100
lacp system-priority 100Switch(config)# lacp system-priority 100 Switch(config)# end Switch# show lacp sys-id 32768, 00:1a:2b:3c:4d:5e
The command sets the system priority to 100. The 'show lacp sys-id' output displays the system priority (100) and the system ID (MAC address). The priority is used in LACP negotiation to elect the active side.
Verifying LACP system priority after configuration
show lacp sys-id100, 00:1a:2b:3c:4d:5e
The output shows the system priority (100) followed by the system MAC address. A lower priority value means higher precedence in LACP negotiations.
Understanding the Output
The 'show lacp sys-id' command displays the LACP system priority and the system identifier (MAC address). The system priority is a 16-bit value from 1 to 65535; the default is 32768. A lower number indicates higher priority. In LACP negotiation, the switch with the lower system priority becomes the active partner (determines which ports are bundled). If priorities are equal, the lower MAC address breaks the tie. When troubleshooting, ensure both ends have compatible priorities; mismatches can cause negotiation failures or unexpected active roles.
CCNA Exam Tips
CCNA exam tip: The default LACP system priority is 32768; changing it can influence which switch controls the bundle.
CCNA exam tip: LACP uses system priority and MAC address to elect the active side; lower priority wins.
CCNA exam tip: You must configure the same LACP system priority on all ports of a switch for consistency.
CCNA exam tip: In exam scenarios, you may need to set a lower priority on the desired active switch.
Common Mistakes
Mistake 1: Forgetting to apply the command in global configuration mode; it will be rejected in interface mode.
Mistake 2: Setting a priority value outside the valid range (1-65535); the switch will reject it.
Mistake 3: Assuming the priority affects PAgP; it only applies to LACP EtherChannels.
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