User's Manual

Networking
IGMP
Cisco ISA500 Series Integrated Security Appliance Administrator Guide 138
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STEP 5 Click Save to apply your settings.
IGMP
The Internet Group Management Protocol (IGMP) is a communication protocol
used by hosts and adjacent routers on IP networks to establish multicast group
memberships. IGMP can be used for online streaming video and gaming, and
allows more efficient use of resources when supporting these types of
applications.
The IGMP Proxy mechanism enables hosts that are not directly connected to a
downstream router to join a multicast group sourced from an upstream network.
IGMP snooping constrains IPv4 multicast traffic at Layer 2 by configuring Layer 2
LAN ports dynamically to forward IPv4 multicast traffic only to those ports that
want to receive it. The IGMP snooping is based on the IGMP version 3 that is
backward compatible with the previous versions.
NOTE By default, the multicast traffic from Any zone to Any zone is blocked by the default
firewall access rules. When you enable IGMP Proxy and want to receive the
multicast packets from WAN to LAN, you need to uncheck the Block Multicast
Packets box in the Firewall -> Attack Protection page, and create a firewall
access rule to permit the multicast traffic from WAN to LAN. For more information,
see Configuring a Firewall Access Rule to Allow the Multicast Traffic, page 185.
STEP 1 Click Networking -> IGMP.
The IGMP window opens.
STEP 2 Enter the following information:
• IGMP Proxy: Click On to enable IGMP Proxy so that your security appliance
can act as a proxy for all IGMP requests and communicate with the IGMP
servers of the ISP, or click Off to disable it.
• IGMP Version: Choose either IGMPv1&v2 or IGMPv3.
- IGMPv1: Hosts can join multicast groups. There are no leave messages.
Routers use a time-out based mechanism to discover the groups that are
of no interest to the members.