Link Failure Response (LFR) Configuration

The LFR feature determines which chassis stack segment front-panel ports will remain enabled should all VSB interconnect links between the VSB chassis go down. All chassis in an operational VSB system stack use the same IP address and function as a single system with the 40GbE interconnect links acting as a virtual backplane for the system. Should all VSB interconnect links between two chassis go down and multiple stack segments remain operational, the stack segments would function as independent network devices with the same IP address.

In a closed ring interconnect configuration as shown in VSB Stacking Data center Configuration Overview, you would need two points of failure for the stack to form multiple segments. The interconnect between the first and last chassis would maintain a single contiguous system in a single point of failure scenario. In a non-closed ring interconnect configuration, any point of failure other than for the first or the last chassis in the system would create multiple stack segments.

When configuring a system of two 7100-Series devices in a VSB system, the LFR feature allows 1 or 10GbE ports to be designated as VSB monitor links that operate in a standby mode to the primary 40GbE VSB ports. The VSB monitor link provides dedicated redundant control plane connectivity and is used only as a backup communication path between bonded chassis in the unlikely event that all of the primary VSB interconnect links fail or become unavailable. When the primary 40GbE VSB ports are down, the VSB monitor links facilitate a communications path to allow the front-panel ports of a single surviving physical chassis segment to remain enabled if the surviving stack segment meets a minimum criteria.

For VSB Stack configurations consisting of more than two 7100-Series devices, LFR monitor links are not used. Instead, LFR uses the cumulative LFR-priority processing described in the sections below.

Whether the front-panel ports of a surviving stack segment remain active or are taken down is based upon the total LFR priority of the surviving stack segment and the total LFR priority of the original VSB stack as follows:

• If the stack segment total LFR priority is greater than half that of the original configured stack total LFR priority, the member switches front-panel ports remain operationally enabled
• If the stack segment total LFR priority is less than half that of the original configured stack, the member switches front-panel ports are disabled
• If the total LFR priority of two stack surviving segments is exactly half of the original configured total, front-panel ports of the stack segment which contains the switch with the highest LFR priority remains operationally enabled

The LFR feature must be globally enabled on each VSB chassis in the VSB system for LFR monitoring to occur. Use the set bonding lfr enable command to globally enable LFR on each physical chassis.

The LFR monitor port is configured using the set bonding port enable command, the same as a VSB interconnect port. What distinguishes the port types in a VSB context is the port speed. The VSB interconnect port must be a 40GbE port and the LFR monitor port must be either a 1 or 10GbE port.

The LFR priority is configurable on a per chassis basis should you wish to provide a higher likelihood of a chassis or group of chassis belonging to the stack segment for which front-panel ports remain enabled.

A chassis‘ LFR priority defaults to 10 times the VSB chassis ID. For example, if the VSB chassis ID is 1, the LFR priority is 10. The LFR priority can be manually set using the set bonding chassis command lfr-priority parameter with a valid range of 1 - 255. Each chassis LFR priority must have an unique value within the stack.