Specifications

ExtremeWare XOS 11.0 Concepts Guide 175
11 Ethernet Automatic Protection Switching
This chapter covers the following topics:
• Overview of the EAPS Protocol on page 175
• Fault Detection and Recovery on page 178
• Multiple EAPS Domains on page 180
• Configuring EAPS on a Switch on page 182
• Configuring EAPS with STP on page 190
Overview of the EAPS Protocol
The Ethernet Automatic Protection Switching (EAPS
TM
) protocol provides fast protection switching to
Layer 2 switches interconnected in an Ethernet ring topology, such as a Metropolitan Area Network
(MAN) or large campuses (see Figure 10).
EAPS protection switching is similar to what can be achieved with the Spanning Tree Protocol (STP),
but EAPS offers the advantage of converging in less than 1 second when a link in the ring breaks.
An Ethernet ring built using EAPS can have resilience comparable to that provided by SONET rings, at
a lower cost and with fewer restraints (such as ring size). The EAPS technology developed by Extreme
Networks to increase the availability and robustness of Ethernet rings is described in RFC 3619: Extreme
Networks’ Ethernet Automatic Protection Switching (EAPS) Version 1.
EAPS operates by declaring an EAPS domain on a single ring. Any virtual LAN (VLAN) that warrants
fault protection is configured on all ring ports in the ring, and is then assigned to an EAPS domain. On
that ring domain, one switch, or node, is designated the master node (see Figure 11), while all other
nodes are designated as transit nodes.