Switching

Hi All,

   Is there a benefit in running LACP between two EX switches?  If I am already configuring the AE's on both sides I can just plug them together and they will form a LAG.  Is there a reason why I should run LACP active/passive, do i gain something from doing this?

LAG is major component defined by IEEE 802.1ad, whereas LACP is a subcomponent of this ...

However, LACP has an importnat role in link aggregation as it detects any miscofiguration of LAG by checking following things: -

1. LAG monitoring, checks whether both ends of the LAGs are connected to the correct group

2. Automatic addition and deletion of individual links to the aggregate bundle without user intervention

see the example in attached figure. here both switch 1 and 2 are configured with LAG including ports ge-0/0/0 and ge-0/0/1 on each. Now by mistake, i connect 0 & 1 on switch-1 with 1 & 2 of switch-2. Now, in the absence of a proper LAG control protocol, LAG will not work properly as all traffic coming out of ge-0/0/1 on switch-1 will be dropped ... In order to control such situation, LACP transmits 1pkt / sec (in active mode) to check whether the other end is part of LAG ...

We should use them in active mode on both ends, as it would help in better resolving such issues. ....

regards

Hi Hafiz

The only correction in your reply is LACP is defined in IEEE 802.3ad.

802.1ad is QinQ.

Apart from these. LACP gives you the option to avoid STP between Switches. 

You may include child interfaces from different VC members to avoid failure scenarios which also avoids unutilized link scenarios unlike STP.

I read seprate thread regarding hitless switchover in case of VC. You will see few drops when STP has to converge. In case you have LACP consisting child interfaces Master and backup. There should not be any packet loss in case of master failure.

pardon Saurabh Joshi