Extreme Networks ExtremeWare XOS 11.3, Руководство пользователя

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RIPng
ExtremeWare XOS 11.3 Concepts Guide
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Advantages of RIPng and OSPFv3
The biggest advantage of using RIPng is that it is relatively simple to understand and to implement,
and it has been the
de facto routing standard for many years.
RIPng has a number of limitations that can cause problems in large networks, including the following:
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A limit of 15 hops between the source and destination networks.
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A large amount of bandwidth taken up by periodic broadcasts of the entire routing table.
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Slow convergence.
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Routing decisions based on hop count; no concept of link costs or delay.
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Flat networks; no concept of areas or boundaries.
OSPFv3 offers many advantages over RIPng, including the following:
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No limitation on hop count.
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Route updates multicast only when changes occur.
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Faster convergence.
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Support for load balancing to multiple routers based on the actual cost of the link.
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Support for hierarchical topologies where the network is divided into areas.
The details of RIPng are explained later in this chapter.
Overview of RIPng
RIPng is primarily intended for use in homogeneous networks of moderate size.
To determine the best path to a distant network, a router using RIPng always selects the path that has
the least number of hops. Each router that data must traverse is considered to be one hop.
Routing Table
The routing table in a router using RIPng contains an entry for every known destination network. Each
routing table entry contains the following information:
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IP address and prefix length of the destination network
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Metric (hop count) to the destination network
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IP address of the next hop router, if the destination is not directly connected
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Interface for the next hop
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Timer that tracks the amount of time since the entry was last updated
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A flag that indicates if the entry is a new one since the last update
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The source of the route, for example, static, RIPng, OSPFv3, etc.
The router exchanges an update message with each neighbor every 30 seconds (default value), or when
there is a change to the overall routed topology (also called
triggered updates ). If a router does not receive
an update message from its neighbor within the route timeout period (180 seconds by default), the
router assumes the connection between it and its neighbor is no longer available.