Take the cheapest exit point

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If this is true, you may want to route traffic out of your autonomous system based on the cheapest exit point, rather than the closest. If you are running a network carrying secure or sensitive data, you might want to have some control over the physical forwarding path the traffic takes once it leaves your network.

Speed of convergence is a very important factor for routing protocols within an autonomous system, while it is not as much of a factor as stability between autonomous systems. In some cases, you may have contracts requiring payment per a given amount of traffic sent on a particular link or set of links.

Avoid accepting redundant or unstable routingThat is within an administrative

This is typically referred to as closest-exit or hot potato routing. Always take the closest exit point. In some cases, combining two or more of these different policies may be required. Take the cheapest exit point.

Don't traverse certain networks. In order to scope resource consumption within your network, you may want to impose policies that discard redundant routing information or suppress unstable route advertisement.

If Partner A and Partner C are actually competitors, the information about Partner C's network could actually be used to compromise their competitive position. This is typically referred to as best-exit routing, though oddly, it's sometimes also referred to as cold potato routing. As such, the routing protocol doesn't need to propagate this information. Take the closest exit point to the final customer. This sort of problem is not only difficult to identify, it is also difficult to fix, since it will involve actions on the part of the network administrators from, possibly, all three routing domains.

That is, within an administrative routing domain intra-domain or between administrative routing domains inter-domain. Avoid accepting redundant or unstable routing information from other networks. The reasoning behind these and many other possible responses will become more obvious as we proceed through the book. Since all the routers contained within the routing domain are under a single administrative control, policies can be implemented on all the routers administratively through manual configuration. For instance, you may want to take the closest cheap exit point, from you network, and not traverse certain other networks.