D will still send updates to router C but it would be with a metric of
"unreachable" or 16 hops for RIP. C will look at this and will:
a) If an update was received from B first, for a better route, it will put
it in the database and drop the "unreachable" packet being sent to it.
b) If an update was received from D, it will enter it into the route as
unreachable, start the holddown timer but will eventually update its
database when it receives an updated route from B. Since B's route will be
better than "unreachable", the holddown timer will be ignored and the route
reinstated.
Hope this answers your question.
As far as triggered update goes, on page 25, #1 of RIP Convergence, it says
"Router D creates a new flash update and sends it to Router E"... that is
upon receiving a flash update from C.
Dyland Desmarais <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Greets all,
>
> I am currently studying for the BCSN exam, have a question . . .
>
> 1. When a distant vector protocol sends out a "flash" update when a
> route goes down, do the neighboring routers who receive the "flash"
> update send out their own updates immediately or do they wait for their
> default update times (ie rip 's is every 30 seconds) to expire.
>
> 2. For those who have a copy of Cisco Press BCSN ISBN:1-57870-228-3:
>
> If you'll consider Figure 1-12 on page 25, why would Routers D and E go
> into holddown if the router mesh is using split horizon?
>
> From what I can tell, Router d would be sending out poisoned reverse
> updates after Router C has updated its route to network 1.1.0.1 with the
> update received from router B. What is preventing Router C from
> changing its route information to what it is receiving from Router D.
>
> Thanx in advance . . .
>
> Dyland
>
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