User guide

A-34 Cisco 2500 Series Access Server User Guide
Desktop Protocols
AppleTalk Routing Protocols
Several AppleTalk routing protocols are available, including the following:
• Routing Table Maintenance Protocol (RTMP)
• AppleTalk Update Routing Protocol (AURP)
• Enhanced IGRP
The default AppleTalk routing protocol on the access server is RTMP. RTMP is a distance
vector algorithm that advertises known extended and nonextended networks in the
internetwork at ten-second intervals. AppleTalk nodes expect to see RTMP packets on the
LAN in order to locate access servers and routers that are routing AppleTalk. Enter the
command show apple route to examine the AppleTalk routing table.
AppleTalk Directory Services
AppleTalk directory services account for a significant portion of the functionality and
usability of AppleTalk. AppleTalk directory services work as follows:
• Networks are assigned one or more zone names.
• Zones can appear on multiple networks.
• After an access server learns of a new route or network from its routing protocol, it will
query the advertising router for the zones associated with that route (network).
• Each router builds a zone information table.
• When an AppleTalk node boots up, it uses the Get Net Info (GNI) routine to ask the
AppleTalk routers on the network what zones are defined for that network. The node
then selects one for itself that will be visible to other AppleTalk devices.
When an AppleTalk node needs directory services, it will ask a local access server or router
routing AppleTalk to execute a lookup. For example, to find LaserWriters in the zone
Marketing, the access server or router will create a packet destined for each network that
has the zone Marketing assigned. Any device that matches this criterion will reply with its
address. Once the device is selected and the address is obtained, the routing takes place on
the network layer addresses, and the zone name is no longer involved in the connection.