D-Link DES-3326S manual Routing Protocols, Protocol-Independent Multicast Dense Mode, 120

DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

other routers will discard multicast packets from that source. If two multicast routers on a network have the same distance back to a multicast source, the router with the lowest IP address is elected.

DVMRP also supports tunnel interfaces, where two multicast routers are connected through a router that cannot process multicast packets. This allows multicast packets to cross networks with routers that are not multicast-aware.

Protocol-Independent Multicast – Dense Mode

There are two protocols in Protocol Independent Multicast (PIM), Protocol Independent Multicast-Dense Mode (PIM-DM) which is used when the multicast destinations are closely spaced, and Protocol Independent Multicast-Sparse Mode (PIM-SM) which is used when the multicast destinations are spaced further apart. PIM-DM is most commonly implemented in an intranetwork (LAN) where the distance between users is minimal.

Routing Protocols

Routing Information Protocol (RIP)

The Routing Information Protocol is a distance-vector routing protocol. There are two types of network devices running RIP – active and passive. Active devices advertise their routes to others through RIP messages, while passive devices listen to these messages. Both active and passive routers update their routing tables based upon RIP messages that active routers exchange. Only routers can run RIP in the active mode.

Every 30 seconds, a router running RIP broadcasts a routing update containing a set of pairs of network addresses and a

120 Switch Management and Operating Concepts