Brocade Communications Systems 8/80 Service Manual download pdf (Page 9)

Chapter 2

Switching and Routing

This chapter describes Layer 2 switching and routing for ServerIron devices. It contains the following sections:

• “MAC switching” on page 2-1

• “STP” on page 2-3

• “Trunk Groups” on page 2-6

• “VLANs” on page 2-6

• “MAC Filters” on page 2-14

• “Address-Lock Filters” on page 2-17

• “Configuring a Broadcast Filter” on page 2-17

• “Setting the Broadcast Limit” on page 2-18

• “Assigning a Gateway List” on page 2-18

• “Multicast” on page 2-19

MAC switching

All Brocade devices support MAC switching. MAC switching enables intelligent wire-speed bridging of Layer 2

packets. The first time a Brocade device receives a packet from a given MAC destination, the device makes an

entry in its Layer 2 cache. The entry consist of the packet’s source MAC address and the port on which the device

received the packet.

When the device receives a bridge packet destined for the cached address, the device does not need to send the

packet as a broadcast through all the ports within the broadcast domain. Instead, the device can intelligently send

the packet only through the port to which the destination device is connected. Thus, even though Layer 2 domains

are typically broadcast domains, MAC switching enhances performance in the domain by reducing the amount of

broadcast traffic in the domain.

In addition, Brocade routers that are enabled for MAC switching can switch traffic for route protocols that are not

supported in the routing software. If IPX routing is disabled on a router, the router can switch the IPX packets

instead.

To avoid accumulating stale cache entries, Brocade devices use an aging mechanism. The aging mechanism

removes a learned entry from the cache after the entry has remained unused for a specified interval (by default,

300 seconds). You can change or disable the aging interval.

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Brocade Communications Systems 8/80 Service Manual Page 9