Cisco BR1400 Deployment Manual page 50

• Configure bridge B as root of link2
• Set the channel on bridge A 5785 MHz or 5805 MHz make sure that link1 and link2 are not
operating at the adjacent channels
• Align bridge B and D by maximizing the RSSI
7.2 Configuration on the wired side for Stacked Bridges
The 1400 Series Bridge provides transparent bridging (fast-switching) between the wired Ethernet
and wireless 802.11a radio interface. The 802.11a radio interface looks like another Ethernet
interface to the transparent bridging module. Transparent Bridging is also supported for 802.1q
tagged VLAN frames. 1400 Series Bridge also supports the 802.1d Spanning Tree Protocol
(STP) along with the Transparent Bridging. This Spanning Tree protocol can inter-operate with
other 802.1q compatible STP (exists on Cisco Switches). STP is also used to provide link level
redundancy for point-to-point bridge environments.
FEC builds upon IEEE 802.3-compliant Fast Ethernet by grouping multiple full duplex point-to-
point links together. FEC is composed of multiple Fast Ethernet links and is capable of load
balancing traffic across those links. Unicast, broadcast, and multicast traffic is evenly distributed
across the links providing higher performance and redundant parallel paths. In the event of a link
failure, traffic is redirected to remaining links within the channel without user intervention. FEC
connections are fully compatible with Cisco IOS virtual LAN technology.
FEC cannot recover from an 802.11a wireless link failure in a timely manner. Packets will be lost
during that period. See the 1400 Series release notes for more information concerning this
limitation. PagP automates the creation of FEC groups. PagP packets are sent between FEC
capable ports in order to negotiate the forming of a channel. If a link is added or fails, PagP
dynamically adds or deletes the link from the FEC group. PagP is currently supported on most of
the Cisco Switches. PagP is not supported on IOS Routers.
PagP can recover automatically from 802.11a wireless link failures, but adds a new problem of not
being able to access the management interface of the 1400 series unit. Manual intervention will be
required to access the management interface of the 1400 series unit, by turning off PagP on the
attached Switch. For PagP, Pegasus transparently bridges the control traffic to the radio link.
Pegasus supports the use of two links in a single FEC.
Basically, there's not much to configure on the Bridges, just ensure that if the bridges are in a
PagP/FEC scenario, then STP should not be enabled on the bridges, but only on the switches
connecting to the bridges. When the 1400 bridges are in a stacked bridge scenario in which the
switches are configured for FEC or PagP, then some of the bridges will not be manageable. The
reason being the switch that does PagP/FEC does not know where the 1400 bridge's IP address is
located either link one or two. It assumes that the link is just a cable as designed. So the packets
destined to the IP address may go to one of the link and the bridges on that link is accessible, but
Copyright © 2004 Cisco Systems, Inc. All rights reserved.
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