When and When Not to Use BGP

When and When Not to Use BGP
BGP is a very complex routing protocol and doesn’t always need to be implemented in order to
route to different autonomous systems. The use of static and default routes is an alternative
to use in place of BGP. The question is, When should you use BGP and when should you use
static or default routes? The answer to that question: It depends on the scenario. Here are a few
instances when static or default routes could be used instead of BGP:
 The routers in your network don’t have much memory and/or processing power. The number
of routes contained in the Internet is huge. If a router doesn’t have enough memory and/or
processing power, it can cause undue delays in your network.
 Your AS is connected to only one other AS, and you do not need to enforce any policies.
 Your network doesn’t have enough bandwidth to support the amount of traffic that BGP
must pass.
Here are a few instances when you would need to implement BGP:
 When you need to enforce inbound and/or outbound policies on information entering or
leaving your network.
 When your network has multiple connections to different autonomous systems, and you
want your autonomous system to pass information from one autonomous system to another
autonomous system. In other words, you want your AS to be a transit AS.
 When connecting different Internet service providers to one another.
These are only a few of the reasons to (or not to) implement BGP. The longer you spend
working with BGP in the real world, the better you will be at spotting when and when not to
use BGP. It’s like anything in life: The more you practice it, the better you will become.
260 Chapter 8  Border Gateway Protocol
A tremendous amount of material has been covered so far in this chapter. It is very important
for you to have a good understanding of the operation of BGP before moving on to the configuration
section of this chapter. If you do not feel comfortable with all of the information covered
so far, stop and review the material. Once you feel comfortable with this information,
move on to the configuration section.