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C H A P T E R 11 Enterprise Standby Router Protocol (ESRP)
183
Figure 11.3: ESRP example using Layer 2 and Layer 3
redundancy
The VLAN Sales master switch, acting as master for VLAN Sales,
performs both Layer 2 switching and Layer 3 routing services for
VLAN Sales. The switch in standby mode for VLAN Sales
performs neither, thus preventing bridging loops in the VLAN. The
switch in standby mode does, however, exchange ESRP packets
with the VLAN Sales master switch.
There are four paths between the VLAN Sales switches. All the
paths are used to send ESRP packets, allowing for four redundant
paths for ESRP communication. The switches near the bottom of
the diagram, being ESRP-aware, allow traffic within the VLAN to
failover quickly, as they will sense when a master/slave transition
occurs and flush FDB entries associated with the uplinks to the
ESRP-enabled VLAN Sales switches.
480t_019
Sales
VLAN
(master)
Sales
VLAN
(standby)
OSPF or RIP
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