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Chapter 6: BGP [ 59 ]
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10.1.1.0
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10.1.1.0
Multihoming
Multihoming means connecting to more than one ISP at the same time. It is
done for redundancy and backup in case one ISP fails and for better
performance if one ISP provides a better path to often used networks. Three
ways exist to receive routes from each ISP:
�¡ Default routes from each provider.This results in low use of bandwidth
and router resources. The internal network�fs IGP metric determines the
exit router for all traffic bound outside the autonomous system.
�¡ Default routes plus some more specific routes.This results in
medium use of bandwidth and router resources. This allows you to
manipulate the exit path for specific routes using BGP, but the IGP
metric chooses the exit path for default routes.
�¡ All routes from all providers.This requires the highest use of bandwidth
and router resources. It is typically done by large enterprises and
ISPs. Path selection for all external routes can be controlled via BGP
policy routing tools.