Routing Information Protocol (RIP) Configuration
159
Software Configuration Guide, Revision 1.03
SN(if-ip)[wan]#
rip poison-reverse
which that information originated. This behavior usually optimizes communications among multiple
routers, particularly when links are broken. However, with non-broadcast networks (such as Frame
Relay), situations can arise for which this behavior is less than ideal. For these situations, you might
want to disable split horizon for RIP.
Procedure
To enable split horizon on an interface
Mode
Interface
Command Purpose
Step 1
node
(if-ip)[
name
]#rip split-
horizon
Enables RIP split-horizon processing on interface
name
Example: Enabling RIP Split-Horizon Processing
The following example shows how to enable split horizon on IP interface
wan
on a SmartNode.
SN(cfg)#
context ip router
SN(ctx-ip)[router]#
interface wan
SN(if-ip)[wan]#
rip split-horizon
18.14 Enabling The Poison Reverse Algorithm
Normally, RIP uses a technique called split horizon to avoid routing loops and allow smaller update
packets. This technique specifies that when the router sends a RIP update out a particular network
interface, it should never include routing information acquired over that same interface.
There is a variation of the split horizon technique called "poison reverse" which specifies that all
routes should be included in an update out a particular interface, but that the metric should be set to
infinity for those routes acquired over that interface. Poison reverse updates are then sent to remove
the route and place it in hold-down. One drawback is that routing update packet sizes will be
increased when using poison reverse.
Procedure
To enable the poison reverse algorithm on an interface
Mode
Interface
Command Purpose
Step 1
node
(if-ip)[
name
]#rip poison-
reverse
Enables the poison reverse algorithm on interface
name
Example: Enabling The Poison Reverse Algorithm
The following example shows how to enable the poison reverse algorithm on IP interface wan on a
SmartNode.
SN(cfg)#
context ip router
SN(ctx-ip)[router]#
interface wan