Extreme Networks ExtremeWare XOS 11.1, Руководство пользователя

Страница: 326 / 496

Extreme Standby Router Protocol
ExtremeWare XOS 11.1 Concepts Guide
326
ESRP and ELRP
Support for the Extreme Loop Recovery Protocol (ELRP) was introduced in ExtremeWare XOS 11.1. For
more information about ELRP, see
“Using ELRP with ESRP” on page 345 . For more information about
standalone ELRP, see “Using Standalone ELRP to Perform Loop Tests” on page 440 .
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.
Figure 44 displays a basic ESRP topology.