Spanning Uplink LAGS Across Both ESU Cards

The system should be configured with LAG ports on both ESU cards, so traffic will continue to flow when the ESUs are switched. This should have done in the initial setup of the system.

Spanning Uplink LAGS protects the system from: 

• Outages due to failure of a single ESU card.
• Outages during software upgrades.

During the software upgrade process, the Active ESU will disable its links during certain parts of the upgrade and the LAG will allow traffic to continue flowing during this part of the upgrade with half the bandwidth.

To create an Uplink (LAG) that spans both cards, create a LAG which includes a port on each card, such as MDS1-ESUA-1 and MDS1-ESUB-1.  This ensures that both cards can actively forward into the uplink and that a single card failure does not cause a failure to pass traffic.
 

WARNING: It is bad practice to have both ports of a LAG on the same card. It means that the system is susceptible to failures of that card during normal operations and upgrades. It will also lengthen the outage times during upgrade significantly.