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Accessible networks allow users to connect
easily over a wide variety of technologies. Campus LAN
users typically connect to routers at the access layer through Ethernet
or Token Ring. Remote users and sites depend on one of
several WAN services. The variety of WAN services will differ from
area to area. Because cost and geography play a significant role in
determining what type of WAN services an organization can deploy,
Cisco routers support all major WAN connection types. As shown in
the figure, these include circuit-switched (dialup) networks, leased
lines (dedicated), and packet switched networks.
- Dialup and dedicated access -
Cisco
routers can be directly connected to basic telephone service or
digital services such as T1/E1. Dialup links can be used for
backup or at remote sites that need occasional WAN access, while
dedicated leased lines provide a high-speed, high-capacity WAN
core between key sites.
- Packet switched - Cisco
routers support Frame Relay, X.25, Switched Multi-megabit Data
Service (SMDS), and ATM. With this variety of support, the WAN service, or combination of WAN services, to
deploy can be determined based on cost, location, and need.
Often, the easier it is for
legitimate remote users to access the network, the easier it is for
unauthorized users to break in. An access strategy must be carefully
planned so that resources, such as remote access routers and
servers, are secure. If a company enables users to telecommute via
dialup modem, the network administrator must secure access routers
with access lists or an authentication protocol such as the Password
Authentication Protocol (PAP) or the Challenge Handshake Protocol
(CHAP). These protocols require the user to provide a valid name and
password before the router permits access to other network
resources.
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