Extreme networks Summit1 Manuale Utente

11-2

S

UMMIT

 S

WITCH

 I

NSTALLATION

 

AND

 U

SER

 G

UIDE

IP M

ULTICAST

 R

OUTING

DVMRP is a distance vector protocol that is used to exchange routing and multicast 
information between routers. Like RIP, DVMRP periodically sends the entire routing 
table to its neighbors.

DVMRP has a mechanism that allows it to prune and graft multicast trees in order to 
reduce the bandwidth that is consumed by IP multicast traffic.

IGMP is a protocol used by an IP host to register its IP multicast group membership 
with the router. Periodically, the router queries the multicast group to see if the group is 
still in use. If the group is still active, a single IP host responds to the query, and group 
registration is maintained.

IGMP snooping adds intelligence to a layer 2 device (such as a switch), to reduce the 
flooding of IP multicast traffic. The goal of IGMP snooping is to optimize the usage of 
network bandwidth and prevent multicast traffic from being flooded to parts of the 
network that do not need to see it.

C

ONFIGURING

 IP M

ULTICASTING

 R

OUTING

To configure IP multicast routing, you must do the following:

Set the devicemode to IP multicasting, using the following command:

config devicemode ipmc

Save and reboot the switch so that the new devicemode configuration occurs.

Configure the switch for IP unicast routing.

For more information on configuring IP unicast routing, refer to 

 and 

Enable multicast routing on the interface, using the following command:

enable ipmcforwarding {vlan <name> | all}

Enable DVMRP on all IP multicast routing interfaces, using the following command:

config dvmrp add [vlan <name> | all]

Summit.bk : 11IPMULT.FM  Page 2  Thursday, June 18, 1998  9:27 AM