User guide

10-2 E
XTREME
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network system design, ESRP can provide better resiliency than using the Spanning
Tree Protocol (STP).
It is highly recommended all switches participating in ESRP run the same version of
ExtremeWare. Not all ESRP features are available in all ExtremeWare software releases.
ESRP-A
WARE
S
WITCHES
Extreme switches that are not running ESRP, but are connected on a network that has
other Extreme switches running ESRP are ESRP-aware. When ESRP-aware switches are
attached to ESRP-enabled switches, the ESRP-aware switches reliably perform fail-over
and fail-back scenarios in the prescribed recovery times. No configuration of this feature
is necessary.
If Extreme switches running ESRP are connected to layer 2 switches that are not
manufactured by Extreme Networks (or Extreme switches that are not running
ExtremeWare 4.0 or above), the fail-over times seen for traffic local to the segment may
appear longer, depending on the application involved and the FDB timer used by the
other vendor’s layer 2 switch. As such, ESRP can be used with layer 2 switches from
other vendors, but the recovery times vary.
The VLANs associated with the ports connecting an ESRP-aware switch to an
ESRP-enabled switch must be configured using an 802.1Q tag on the connecting port,
or, if only a single VLAN is involved, as untagged using the protocol filter
any
. ESRP
will not function correctly if the ESRP-aware switch interconnection port is configured
for a protocol-sensitive VLAN using untagged traffic.
ESRP B
ASICS
ESRP is configured on a per-VLAN basis on each switch. A maximum of four switches
can participate in providing redundant layer 3 or layer 2 services to a single VLAN. The
switches exchange keep-alive packets for each VLAN independently. Only one switch
can actively provide layer 3 routing and/or layer 2 switching for each VLAN. The
switch performing the forwarding for a particular VLAN is considered the “master” for
that VLAN. Other participating switches for the VLAN are in standby mode.
For a VLAN with ESRP enabled, each participating switch uses the same MAC address
and must be configured with the same IP address or IPX NetID. It is possible for one
switch to be master for one or more VLANs while being in standby for others, thus
allowing the load to be split across participating switches.