Intel 480T, Руководство пользователя

Страница: 202 / 367

200
C H A P T E R 1 1 RIP and OSPF
Split Horizon
Split horizon is a scheme for avoiding problems caused by
including routes in updates sent to the router from which the route
was learned. Split horizon omits routes learned from a neighbor in
updates sent to that neighbor.
Poison Reverse
Like split horizon, poison reverse is a scheme for eliminating the
possibility of loops in the routed topology. In this case, a router
advertises a route over the same interface that supplied the route,
but the route uses a hop count of 16, defining it as unreachable.
Triggered Updates
Triggered updates occur whenever a router changes the metric for a
route, and it is required to send an update message immediately,
even if it is not yet time for a regular update message to be sent. This
will generally result in faster convergence, but may also result in
more RIP-related traffic.
Route Advertisement of VLANs
VLANs that are configured with an IP address, but are configured
to not route IP or are not configured to run RIP, do not have their
subnets advertised by RIP. Only those VLANs that are configured
with an IP address and are configured to route IP and run RIP have
their subnets advertised.
RIP Version 1 Versus RIP Version 2
A new version of RIP, called RIP version 2, expands the
functionality of RIP version 1 to include the following:
• Variable-Length Subnet Masks (VLSMs)
• Support for next-hop addresses, which allows for optimization of
routes in certain environments.