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When a device on the network attempts to discover services (such as servers or printers) using a Chooser program, an NBP (Name Binding Protocol) lookup packet is sent to a router on the same segment, which then performs a lookup in its tables to determine the network number(s)/range(s) for a partic- ular zone. These tables are maintained using the ZIP (Zone Information Protocol).
The lookup is then forwarded to the appropriate segment(s). Devices whose services match the information in the lookup will respond to it, and the response will be forwarded back to the original machine.
Router Autoconfiguration
An autoseeding default router configuration simplifies administration of routers since AppleTalk can be routed right out of the box without any addi- tional configuration.
To determine a network number to use for autoseeding, a router listens to the network for several RTMP periods, and then examines its routing table (which is filled in with information from RTMP packets), and picks an unused number for each interface. Only Phase 2 extended networking is turned on in the default configuration, with network ranges of 1.
A default zone name is created for each interface that incorporates the router’s Ethernet address, which is guaranteed to be unique.
Bridging 101
ϖNote: This is a very brief introduction to the concept of bridging networks. For more
Bridging Basics
Bridges are used to limit the amount of traffic appearing on network segments other than the destination segment. They do not provide for the logical grouping of network devices, which makes them considerably less flexible than routers from the standpoint of network management.
In contrast to routers, bridges operate on the “physical” network layer. While protocols such as IP or IPX are concerned with their own addressing schemes and routing tables (see IP 101 or IPX 101), bridging is only concerned with physical (i.e. Ethernet) addresses, and which bridge interface they are located on.
