3Com 530, 510, 520 manual Figure A-4 Open Systems Interconnection Network Layer Model

A-8 BRIDGING AND ROUTING

It is important to understand that in a bridged network the addressing structure for both IP and IPX relates to a single network. If the units in Figure A-3were bridges and not routers, then an IP node on LAN A could, for example, have an address 140.56.10.0, the node on LAN B an address 140.56.10.2, and the node on LAN C, an address of

140.56.10.3.All the nodes, therefore, are able to share the same Class B network address, regardless of their location on the bridged network.

However, if there were NetWare nodes throughout the three bridged sites, they would also share the same IPX network number. If each of the bridged LANs supported a network server, each with its own unique network number, and an IPX address is misconfigured, the NetWare network server consoles will report the message ‘Router Configuration Error – Router XXXXX claims that LAN is XX-XX-XX-XX’. (The router it refers to is in fact the network server).

APPLICATION

PRESENTATION

SESSION

TRANSPORT

NETWORK

DATALINK

PHYSICAL

Network	File
	Transfer
File Store		Telnet
	Protocol
(NFS)
	(FTP)

User	Transmission
Database	Control
Protocol	Protocol
(UDP)	(TCP)

Internet Protocol (IP) and

Internet Control Message Protocol

(ICMP)

Link Level Control

Ethernet	Others
Hardware

ARP

RARP

Figure A-4 Open Systems Interconnection Network Layer Model