Gateway Redundancy

Redundancy is a large part of enterprise network design. When designing enterprise networks, single points of network failure should be avoided whenever possible, particularly when network hardware is involved. You should recall from Chapter 6 that Layer 2 redundancy can be accomplished quite easily by connecting duplicate backbone links. The spanning-tree algorithm used in most bridges and switches today by default will disable one of the links, leaving it in a suspended state. In case of a failure, the suspended link is enabled and service is restored. At Layer 3, it is possible to have gateways and nodes share routing information. AppleTalk and IPX behave this way by default. With IP, it is a little more difficult, because ...

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