CCIE: May 12, 2012

Saturday, May 12, 2012

IGMP: Internet Group Management Protocol

IGMP is automatically enabled when PIM enabled.
IGMP enables the communication between multicast routers and their hosts.
Multicast routers uses the IGMP to send ip packets to what multicast groups on what interfaces.
Host Membership query:

Routers use the queries to discover the presence of multicast group member on a subnet.
general membership query is sent to the group address 0.0.0.0.
group specific query is sent to the group address that is required.

Host Membership Reports:

Hosts replies to queries.

RESERVED MULTICAST ADDRESSES

224.0.0.1 - All multicast hosts
224.0.0.2 - All multicast routers
224.0.0.4 - DVMRP routers
224.0.0.5 - OSPF routers
224.0.0.6 - OSPF DR routers
224.0.0.9 - RIPv2 routers
224.0.0.10 - EIGRP routers
224.0.0.13 - PIM routers
224.0.0.22 - IGMPv3
224.0.0.25 - RGMP
224.0.0.39 - Auto-RP announce (RP)
224.0.0.40 - Auto-RP Discovery (MA)

MULTICASTING

multicast is udp based
source address is always unicast address & never be multicast address.
commands used are:

sh ip mroute // show the multicast routing table
sh ip multicast interface // shows multicast details for the interface
clear ip mroute * // clear routes from the multicast routing table
ip multicast-routing // globally enables multicast routing on router
ip multicast-routing distributed // globally enables multicast routing on a 3560

DIFFERENCE BETWEEN PIM-DM & DVMRP

DVMRP uses its own dinstance vector protocol.

update routes for every 60 seconds
maximum 32 hops only

dvmrp uses probe messages to find neighbors

DVMRP

cisco ios does not support a full implementation of DVRMP
but it support connectivety to a dvmrp network.
cisco routers enough know about dvmrp to successfully forward multicast packets to and receive pakets from a dvmrp neighbour.
dvmrp routes are propagate into & through PIM cloud.
these dvmrp routes are maintained in a seperating routing table on each cisco router.

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