ESRP Master Election
The system determines the ESRP (Extreme Standby Router Protocol) master switch (providing Layer 3 routing
and/or Layer 2 switching services for a VLAN (Virtual LAN)) using the following
default factors:
- Stickiness—The switch with the higher sticky value has higher
priority. When an ESRP domain claims master, its sticky value is set to 1 (available only in
extended mode).
- Active ports—The switch that has the greatest number of active ports
takes highest precedence.
- Tracking information—Various types of tracking are used to determine
if the switch performing the master ESRP function has connectivity to the outside world.
ExtremeXOS software supports the following types of tracking:
- VLAN—Tracks any active port connectivity to one designated VLAN.
An ESRP domain can track one VLAN, and the tracked VLAN should not be a member of any
other ESRP domain in the system.
- IP unicast route table entry—Tracks specific learned routes from
the IP route table.
- Ping—Tracks ICMP (Internet Control Message Protocol) ping connectivity to specified
devices.
- Environment (health checks)—Tracks the environment of the switch,
including power supplies.
If any of the configured tracking mechanisms fail, the master ESRP switch relinquishes
status as master, and remains in slave mode for as long as the tracking mechanism continues
to fail.
- ESRP priority—This is a user-defined field. The range of the priority
value is 0 to 255; a higher number has higher priority, except for 255. The default priority
setting is 0. A priority setting of 255 makes an ESRP switch a standby switch that remains
in slave mode until you change the priority setting. We recommend this setting for system
maintenance. A switch with a priority setting of 255 will never become the master.
- System MAC address—The switch with the higher MAC address has higher
priority.
- Active port weight—The switch that has the highest port weight takes
precedence. The bandwidth of the port automatically determines the port weight (available
only in extended mode).
You can configure the precedence order of the factors used by the system
to determine the master ESRP switch. For more information about configuring the ESRP election
metrics, see ESRP Election Algorithms.
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