LACP system-priority

[gohgss2010]

If I have existing etherport channel switch uplink, and I configure lacp will there any impact?

if lacp sys-id already 32768, do I need configure lacp system-priority value still?

sh lacp sys-id

32768, 1cdf.0ffd.d180

How do I determine lacp system-priority value? Should I configure as 23456 as example?

Examples

Router> enable
Router# configure terminal
Router(config)# lacp system-priority 23456
Router(config)# interface g4/0/0
Router(config-if)# lacp port-priority 500
Router(config-if)# end

[Reza Sharifi]

You usually don't need to worry about changing sys-id.  you Just configure one side of the connection as active and the other side as passive.

HTH

[InayathUlla Sharieff]

Hi,

Please find the details for your query:-

There will be no impact on the command/changing the LACP system priority.  Below is the explanation on what it does:-

LACP system priority:
 
A LACP system priority is configured on each router running LACP. The system
priority can be configured automatically or through the CLI. LACP uses the
system priority with the router MAC address to form the system ID and also
during negotiation with other systems. 
 
The LACP system ID is the combination of the LACP system priority value and
the MAC address of the router. 
 
LACP port priority: 
 
A LACP port priority is configured on each port using LACP. The port
priority can be configured automatically or through the CLI. LACP uses the
port priority with the port number to form the port identifier. The port
priority determines which ports should be put in standby mode when there is
a hardware limitation that prevents all compatible ports from aggregating.  
If you come up with more questions, please refer to the following links for
full instructions on and examples of how to configure LACP:
 
 
Link Aggregation Control Protocol (LACP) (802.3ad) for Gigabit Interfaces:
http://www.cisco.com/en/US/docs/ios/12_2sb/feature/guide/gigeth.html 
Layer 3 and Layer 2 EtherChannel:
http://tools.cisco.com/squish/F3588

b)

The switch with the lowest lacp system-priority makes the decision about which ports are actively participating in the etherchannel at any given time.

Hope this helps.

Plz rate if this helpfull.

Regards

Inayath.

[gohgss2010]

Can I not configure? Is there any purposes for this configuration?

Router(config)# lacp system-priority 23456

but this only, will it be any issue?

Router(config)# interface g4/0/0

Router(config-if)# lacp port-priority 500

[InayathUlla Sharieff]

Hi,

As I said earlier that the port priority determines which ports you should be using when you have more than 8 links connectd/bundled using etherchannel.

Here is the example which might help you:

============================

Say SW1 has a system priority if 32768 (default) + its switch MAC address, this is similar to STP bridge ID. SW2 has a priority of 100 + MAC address, SW2 will become the decision maker since it has the lowest ID.

SW1 has ports 1 - 9, as does SW2, configured for etherchannel. The decision maker, the switch with the lowest priority, picks which eight of nine ports are active. The ports are picked based on lowest priority, 32768 + the port number, if the priority is at its default then the lowest port number wins and the other is set to stand by.

hope this helps.

Regards

Inayath