[c-nsp] holdtime for DIS in ISIS

[Oliver Boehmer (oboehmer)]

cisco-nsp-bounces at puck.nether.net <> wrote on Monday, November 06, 2006
7:17 AM:

> Hi all,
> 
> I'm having a small network where 3 - 7200 boxes are connected
> to each other
> via a 2950 switch and running ISIS on pretty much default
> configuration. All 3 routers have established L1 adjacency only with
> each other. 
> 
> One of the routers (RouterA) has been forced to be DIS on this LAN by
> increasing its priority to 127 (isis priority 127 interface
> conf. command).
> 
> Now the question is that why "holdtime" of the DIS for its 2 neighbors
> appears to be lot lesser than the normal hold time for ISIS adjacency.
> Following is output from one of the neighbors (RouterC) of
> DIS (RouterA):
> 
> Due to presence of a wireless link (end-to-end Ethernet which
> is not in a good condition) between RouterA and RouterC, the L1
adjacency between
> RouterA and RouterC often breaks.
> 
> Any help? Should I increase the hello-multiplier of RouterA
> to increase the holdtime? What is the actual reason of holdtime to be
lesser
> incase of a DIS?

For the DIS, IOS actually uses a third of the configured hello interfal.
This was made to make sure DIS failure is detected more quickly. If this
doesn't work for you, please increase the hello-interval/multiplier on
the DIS..

	oli