Extreme Networks ExtremeWare XOS 11.3, Руководство пользователя

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Extreme Standby Router Protocol
ExtremeWare XOS 11.3 Concepts Guide
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ESRP Modes of Operation
ExtremeWare XOS has two modes of ESRP operation: standard and extended. Select standard ESRP if
your network contains some switches running ExtremeWare, others running ExtremeWare XOS, and a
combination of those switches participating in ESRP. Standard ESRP is backward compatible with and
supports the ESRP functionality of ExtremeWare.
Select extended ESRP if your network contains switches running only ExtremeWare XOS. Extended
mode ESRP supports and is compatible with switches running ExtremeWare XOS. By default,
ExtremeWare XOS operates in extended mode.
In addition to the modes of operation, ESRP has an auto toggle feature. Depending on the mode of
operation configured on the neighbor switch, the mode of operation at this end will toggle to the same
mode of operation as the neighbor.
For more detailed information about the ESRP modes of operation, see “Standard and Extended ESRP”
on page 459 .
ESRP and ELRP
Support for the Extreme Loop Recovery Protocol (ELRP) was introduced in ExtremeWare XOS 11.1.
ELRP allows you to prevent, detect, and recover from Layer 2 loops in the network. For more
information about configuring ELRP in an ESRP environment, see
“Using ELRP with ESRP” on
page 476 . For more information about standalone ELRP, see “Using Standalone ELRP to Perform Loop
Tests” on page 620 .
Reasons to Use ESRP
You can use ESRP to achieve edge-level or aggregation-level redundancy. Deploying ESRP in this area
of the network allows you to simplify your network design, which is important in designing a stable
network. ESRP also works well in meshed networks where Layer 2 loop protection and Layer 3
redundancy are simultaneously required.
ESRP Concepts
You configure ESRP on a per domain basis on each switch. A maximum of two switches can participate
in providing redundant Layer 3 or Layer 2 services to a single Virtual LAN (VLAN). If you configure
and use ESRP groups, more than two switches can provide redundant Layer 2 or Layer 3 services to a
single VLAN. The switches exchange keep-alive packets for each VLAN independently. Only one switch
(the master) can actively provide Layer 3 routing and/or Layer 2 switching for each VLAN. This switch
handles the forwarding, ARP requests, and routing for this particular VLAN. Other participating
switches for the VLAN are in slave mode waiting for an ESRP state change.
For a VLAN within an ESRP domain, 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 a master switch
for one or more VLANs while being a slave switch for other VLANs, thus allowing the load to be split
across participating switches.