SummaryUsing Link Aggregation (LACP 802.3ad, and the various technologies based off of it) require settings such as Global QoS and depending on the topology, Dual Bridge Bypass to be set up.
OverviewLink aggregation technologies (LACP, Etherchannel, PAgP, 'NIC teaming', etc), based on the 802.3ad protocol, allow for multiple individual bandwidth links to be logically combined into a single logical link (ie, 4 ports on a switch can be grouped together as one 'logical' link that is 4x the bandwidth). This helps with removing congestion and increasing redundancy, as well as increasing efficiency by not wasting empty ports on devices.
While the Exinda supports link aggregation, it is possible to see slow performance if the Exinda is not configured correctly to handle aggregate links. This can be seen through slow access, bandwidth drops and bottlenecks at the device.
CauseThe Exinda appliances support link aggregation, but because only one cable can go into a specific bridge in either direction (either LAN or WAN), it is required for the various physical links belonging to the aggregate be plugged into different bridges. This leads into various problems with configuration because different optimization can happen on different bridges, depending on how the policy tree has been set up. This means that if traffic end ups traversing multiple bridges due to how the traffic is flowing over the aggregate link, it is possible that the traffic will be optimized twice and as a result, it can be shaped down to an extremely slow point.
ResolutionIf using link aggregation through an Exinda, ensure the following:
- Global QoS is applied (Configuration > System > Setup, "Control" tab). This will ensure that a single set of policies will apply to all bridges on the device, so regardless of the bridge the traffic goes over, it will be shaped the same way.
If acceleration is used as well
- Dual bridge bypass is applied (Configuration > System > Setup, "Monitoring" tab), if the aggregate link might require two passes through the Exinda. This will stop the slowness in cases where traffic is travelling through the Exinda more than once and getting shaped multiple times. The second (or later) passes through the Exinda will be 'ignored' from a QoS perspective)