System information

© Copyright IBM Corp. 2000 25
Chapter 3. Ethernet switch interoperability
In this chapter we consider a basic, flat layer-2 switched Ethernet LAN. In the
previous chapter we went through several of the characteristics of Ethernet
switches that we should consider for interoperability in this environment.
The size of a flat layer-2 Ethernet LAN is usually limited by the broadcast
activity to a few hundred MAC addresses, but single broadcast domains of
several thousand have been heard of.
Joining several layer-2 domains in installations with Ethernet switches from
IBM has traditionally been accomplished with classical layer-3 routers such
as IBM 2216, or the IBM 8274 RouteSwitch, or through an ATM backbone
with the Multiprotocol Switched Services (MSS) server. Interoperability of
traditional layer-3 routers is the subject of a recently published redbook
IBM
Router Interoperability and Migration Examples
, SG24-5865. The
employment of ATM and the MSS is discussed in Chapter 4, “AT M LA N
backbone interoperability and migration” on page 67.
In this redbook we do not consider in detail the layer-3 and layer-4 functions
of the IBM 8371 switch since these are not widely deployed, having been
available only after the IBM-Cisco alliance was announced.
In “Scenario 1: Single subnet - step-by-step box addition” on page 25 and
“Scenario 2: Multiple subnets - growth environment” on page 26, we discuss
two generalized scenarios. In “Basic Ethernet interoperability exercises” on
page 27 we describe in some detail two interoperability laboratory exercises
that we performed, and we discuss our experiences.
Please contact your IBM or Cisco representative to get the latest information
about the interoperability tests performed jointly by IBM and Cisco, and for
instructions on submitting requests for new interoperability tests.
3.1 Scenario 1: Single subnet - step-by-step box addition
This scenario describes the case where we have an Ethernet LAN with a
single broadcast domain. The backbone is a single or a few switches, for
instance IBM 8271. Workstations are often on shared segments made up of
hubs such as IBM 8237.
Generally you find this type of LAN in small businesses or in branch offices.
There is no immediate demand for new functions or significantly increased
performance. Workstations often run at 10 Mbps, but there is a general trend