The default IGRP timer intervals are as follows:
Update Timer (90 seconds) How often the router is to initiate routing table updates.
Hold Timer (280 seconds: 3 x Update Timer + 10 seconds) The amount of time the IGRP routing table will hold down routing updates.
Route Invalid Timer (270 seconds: 3 x Update Timer) The amount of time a router will wait, in the absence of routing update messages about a specific route, before declaring the route invalid.
Route-Flush Timer (630 seconds: 7 x Update Timer) The amount of time before a route is flushed from the routing table.