Information Technology Reference
In-Depth Information
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5
Enterprise BGP Core Network
Design
Enterprises have typically favored the use of IGPs to provide company-wide IP connectiv-
ity. The case for BGP is often made when an enterprise has reached scalability limitations
within its IGP. BGP provides enhanced scalability when there are high prefix counts and
improves the enterprise's ability to divide administrative control.
Network scalability is improved through increasing network hierarchy and better prefix
summarization. Summarization in many networks can be very challenging because of past
address assignments that do not provide adequate summarization boundaries. However,
BGP can increase scalability by adding hierarchy in the network core.
Enterprises also face the challenge of diversified administrative control. An enterprise
might have separate engineering and operations centers in different geographic regions,
each with administrative control over a portion of the network. An enterprise network also
can consist of a central core network with any number of individual networks, each under
the control of different administrative groups. When control is distributed in this fashion,
having a common IGP process can present significant operational issues. As mentioned in
earlier chapters, BGP was designed with the goal of diverse administrative control.
This chapter examines when you should consider BGP as a solution and how to implement
such a solution in an enterprise core network. You'll see extensive examples that demon-
strate how you should use BGP to develop stable and scalable core network architectures.
Using BGP in the Enterprise Core
Enterprise engineers and architects often ask, “When should I use BGP in the enterprise
core?” Although this is a very common question, the answer is not an easy one. Many
factors go into determining the correct routing architecture for an enterprise network, as
discussed in the next sections.
