Timers

The CSNP on multiaccess networks

The CSNP (Complete Sequence Number PDU) on multi-access networks is being sent out on behalf of the DIS (Designated Intermediate System), which acts as the pseudonode representing the multi-access network. Its being used as ISIS’s way of making sure everybody on the multi-access network is up to date. If thats not the case, the node which is missing some routing information can use PSNP (Partial Sequence Number PDU)’s to request the missing information from the DIS.

In this short post i want to try and shed some light on a couple of ISIS timers that had me confused at first. I think i got them down now, but please let me know if i have misunderstood them.