[c-nsp] Reasons for "random" ISIS flapping?

[Adam Vitkovsky]

>> The device in question has a rather large-ish amount of SPD drops (42
>> ppm) according to "show ibc", but other devices in the network have 
>> much
>I'd try to increase hold-queue. 

I would not recommend to increase hold-queue as that might lead to increased
delay or delay variation, by a mere fact of increasing a pipe where
high-priority packet might get stuck waiting to get processed and switched.
And the larger the buffer the bigger is the delay variation. 

Instead you might try to increase "spd extended headroom" from the default
10 (cmd: "spd extended") which is solely responsible for holding non-IP
packets such as CLNS datagrams (e.g. IIHs) when input "hold queue" and "spd
headroom" buffers are full already. 

You can check the queue values with cmd:"sh ip spd". 
 
adam