about hold down timers

[huangzhy]

In rip operation ,according to cisco ios command reference(timers basic command):

A route enters into a hold-down state when an update packet is received that indicates the route is unreachable. The route is marked inaccessible and advertised as unreachable.

But according to the book ROUTING TCP/IP Volume 1 written by Jeff Doyle,it says: If the distance to a destination increases(for example,the hop count increses form 2 to 4),the router sets a holddown timer for that route.Until the timer expires,the router will not accept any new updates for the route.

So the above two theory conflict with each others.

When on earth the router sets a hold down timer for a route when the route is unreachable or just when the distance to a destination increases?

[mmellet]

When I checked the above, I found the following:

1. When the nework is suddenly unreachable, after the hold down timer expires - the routing tabler displays it as X.X.X.X is possibly down.

2. But when the next hop router advertises witha higher hop count than in the exixting routing table, It doesnt sets a holddown timer for the already existing route. Rather the new higher hop count is installed in the routing table.