IS-IS Flooding

Link-state protocols are flooded to provide the routers a constant view of the network. Routers within the level domain need to synchronize the level 1 database; similarly, all level 2 routers must have consistent information. Flooding and synchronization of the database are done via CSNP, PSNP, SSN, and SRM bits.

In any link-state protocol, when new LSPs are received, they are flooded to all the neighbors. It is necessary that all the ISs receive information about all the LSPs. The behavior of the LSP flood is forwarded to all the neighbors, except the one LSP from which the packet has been received.

Send Sequence Number (SSN) and Send Routing Message (SRM) bits are new to this discussion. The SRM bit is set in an interface ...

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