User guide

A-24 Cisco 2500 Series Access Server User Guide
Desktop Protocols
The function of the routing protocol is to build a complete routing table in each access
server or router. The routing table is a pointer to every network in an internetwork. For
example, the IP routing table for Router B in Figure A-8 might look as follows:
network cost next hop interface
172.16.10.0 01 RouterA f0
172.16.20.0 00 connected t0
172.16.30.0 00 connected f0
172.16.1.0 00 connected s0
172.16.2.0 00 connected s1
172.16.40.0 01 RouterC s0
172.16.40.0 01 RouterD s1
In order to achieve two-way connectivity between two end nodes and therefore the ability
to exchange packets on an internetwork, every access server or router in the path between
the nodes must have a routing table entry that describes how to forward a packet addressed
to both nodes. Connectivity also depends on the correct operation of ARP to deliver the
packet within the networks at either end of the packet’s path.
Directory Services
Nodes on an internetwork use directory services to locate specific services such as file
servers, printers, and e-mail servers. Each protocol (IP, IPX, and AppleTalk) has a unique
way of doing this. For IPX and AppleTalk, support of directory services is a critical part of
the design considerations.
Internet Protocol
IP is used by the Internet (the world’s largest internetwork, which connects thousands of
networks worldwide) and within many companies. Its addressing scheme scales well for
global addressing although, like the telephone industry, address space is running out.
IP uses centrally administered major network numbers to allow internetworks to connect to
the Internet. If you require Internet connectivity, you will need to get network address space
from an organization called the InterNIC (the InterNIC controls address allocation for the
Internet). If you do not plan to have Internet connectivity, or if you have limited assigned
address space, see RFC 1597 for numbering suggestions.