Asante Technologies 35516 - Manual (Page 60)

- 60 -
To do this, perform the following task in router configuration mode.
Command Purpose
distribute-list {access-list-name | prefix
prefix-list-name} in | out}
[interface-name] Suppress routes from being advertised and processed in
routing updates depending upon the action listed in the
access list or prefix list.
Apply Offsets to Routing Metrics
An offset list is the mechanism for increasing incoming and outgoing metrics to routes learned via RIP. You can limit
the offset list with an access list. To increase the value of routing metrics, perform the following task in router
configuration mode.
Command Purpose
offset-list access-list-name { in | out} Apply an offset to routing metrics.
5.4.9 Adjust Timers
Routing protocols use several timers that determine such variables as the frequency of routing updates, the length of
time before a route becomes invalid, and other parameters. These timers can be adjusted to fine-tune the routing
protocol performance to better suit the inter-network needs.
The default settings for the various timers are as follows:
• The update timer is 30 seconds. During every update, the RIP process sends an unsolicited response message
containing the complete routing table to all neighboring RIP routers
• The timeout timer is 180 seconds. Upon expiration of the timeout, an unresponsive route becomes invalid;
however, it is retained in the routing table for a short time so that neighbors can be notified that the route has
been dropped
• The garbage collect timer is 120 seconds. Upon expiration of the garbage-collection timer, the unresponsive
route is finally removed from the routing table
To adjust the timers, use the following command in router configuration mode.
Command Purpose
timers basic update timeout garbage Adjust routing protocol timers.
5.4.10 Enable or Disable Split-horizon
Normally, routers that are connected to broadcast-type IP networks, and that use distance-vector routing protocols,
employ split horizon with poison reverse to reduce the possibility of routing loops.
The split horizon with poison reverse mechanism blocks information about routes from being advertised by a router
out any interface from 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, a user might want to disable split
horizon. If an interface is configured with secondary IP addresses and split horizon is enabled, updates might not be
sourced by every secondary address. Only one routing update is sourced per network number, unless split horizon is
disabled.