RIP holddown timer ?

Hello Experts,

Can someone please help me understand how RIP holddown timer works? The
definition in the tcp/ip vol1 1 is:
"If a route is declared unreachable or if the metric increases beyond a
certain threshold, a router will not accept any other information about that
route until the holddown timer expires."

I have this topology to test it:

 /---R2----R3---\ <- eth
R1 R4
 \--------------/ <- FR

R1 advertises 1.1.1.0/24
All interfaces are UP
R4 installs 1.1.1.0 in the routing table with metric 1 via R1

If R1 shuts Serial int (direct to R4), R4 will set the route as un-reachable
after the "invalid timer" expires and marks then the route as "possibly
down". At this point hold timer kick in.

My problem is that R4 will NOT WAIT until hold timer expires before
installing new route (via R3 and R2). R4 will install 1.1.1.0 with metric 3
immediately when it receives next updated from R3.

What is wrong ?

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Received on Fri Mar 18 2011 - 11:42:13 ART