Garbage, timeout, and update timers
RIP uses various timers to regulate its performance including a garbage timer, timeout timer, and update timer. The FortiGate unit default timer settings (30, 180, and 120 seconds respectively) are effective in most configurations — if you change these settings, ensure that the new settings are compatible with local routers and access servers.
| The Timeout period should be at least three times longer than the Update period. If the Update timer is smaller than Timeout or Garbage timers, you will experience an error. |
You can set the three RIP timers in Router > Dynamic > RIP, under Advanced Options, or use the CLI.
The CLI commands associated with garbage, timeout, and update timers include:
config router rip
set garbage-timer
set timeout-timer
set update-timer
end
Garbage timer
The garbage timer is the amount of time (in seconds) that the FortiGate unit will advertise a route as being unreachable before deleting the route from the routing table. If this timer is shorter, it will keep more up-to-date routes in the routing table and remove old ones faster. This will result in a smaller routing table which is useful if you have a very large network, or if your network changes frequently.
Update timer
The update timer determines the interval between routing updates. Generally, this value is set to 30 seconds. There is some randomness added to help prevent network traffic congestion, which could result from all routers simultaneously attempting to update their neighbors. The update timer should be at least three times smaller than the timeout timer, otherwise you will experience an error.
If you are experiencing significant RIP traffic on your network, you can increase this interval to send fewer updates per minute. However, ensure you increase the interval for all the routers on your network or you will experience time outs that will degrade your network speed.
Timeout timer
The timeout timer is the maximum amount of time (in seconds) that a route is considered reachable while no updates are received for the route. This is the maximum time the FortiGate unit will keep a reachable route in the routing table while no updates for that route are received. If the FortiGate unit receives an update for the route before the timeout period expires, the timer is restarted. The timeout period should be at least three times longer than the depute period, otherwise you will experience an error.
If you are experiencing problems with routers not responding in time to updates, increase this timer. However, remember that longer timeout intervals result in longer overall update periods — it may be considerable time before the time the FortiGate unit is done waiting for all the timers to expire on unresponsive routes.