Information Technology Reference
In-Depth Information
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6
Internet Connectivity for
Enterprise Networks
The integration of day-to-day business communication with the Internet has made highly
redundant Internet connectivity a mission-critical service. The use of e-mail and the web
have become tightly integrated into the world economy and the way business is done. It is
in this capacity—connecting to the Internet—that BGP is most commonly seen in enter-
prise environments.
This chapter presents the design options that are available and explains the central concepts
of each option. The caveats associated with each design are also presented, in addition to
any requirements, such as needing a unique public autonomous system number (ASN).
Determining What Information to Accept from
Upstream Providers
Questioning what information to accept from upstream providers is very common. When
you make routing decisions, the availability of more-specific information provides the
potential for increased optimization in determining which path to use in reaching a destina-
tion. However, this increase in information results in the trade-off of higher resource
requirements, both system and administrative. Three options are explored here:
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Default route only
•
Default plus partial routes
•
Full Internet tables
Default Route Only
The option of default routing only can be used with or without BGP. The default route is
either statically defined or received via BGP from the provider. The default route is injected
into the IGP, directing traffic to the closest border router. The use of default routing requires
minimal system resources but can result in suboptimal routing.
