Extreme Networks ExtremeWare XOS 11.3, Manual

Page: 463 / 698

Determining the ESRP Master
ExtremeWare XOS 11.3 Concepts Guide
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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” on page 465 .
Master Switch Behavior
If a switch is master, it actively provides Layer 3 routing services to other VLANs, and Layer 2
switching between all the ports of that VLAN. Additionally, the switch exchanges ESRP packets with
other switches that are in slave mode.
Pre-Master Switch Behavior
A pre-master switch is ready to transition to master, but is going through possible loop detection prior
to changing to the master state. Upon entering the pre-master state, the switch sends ESRP packets to
other switches on that same VLAN. If the switch finds itself superior to its neighbor, and successfully
executes loop detection techniques, the switch transitions to master. This temporary state avoids the
possibility of having simultaneous masters.
Slave Switch Behavior
If a switch is in slave mode, it exchanges ESRP packets with other switches on that same VLAN. When
a switch is in slave mode, it does not perform Layer 3 routing or Layer 2 switching services for the
VLAN. From a Layer 3 routing protocol perspective (for example, RIP or OSPF), when in slave mode
for the VLAN, the switch marks the router interface associated with that VLAN as down. From a Layer
2 switching perspective, no forwarding occurs between the member ports of the VLAN; this prevents
loops and maintains redundancy.
If you configure the switch to use the optional ESRP HA configuration, the switch continues Layer 2
forwarding to the master. For more information, see
“ESRP Host Attach” on page 473 .
Neutral Switch Behavior
The neutral state is the initial state entered into by the switch. In a neutral state, the switch waits for
ESRP to initialize and run. A neutral switch does not participate in ESRP elections. If the switch leaves
the neutral state, it enters the slave state.
Electing the Master Switch
A new master can be elected in one of the following ways:
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A communicated parameter change
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Loss of communication between master and slave(s)
If a parameter determines the master changes (for example, link loss or priority change), the election of
the new master typically occurs within one second. A parameter change triggers a handshake between
the routers. As long as both routers agree upon the state transition, new master election is immediate.