Asante Technologies IC36240 user manual Using Access Lists, Host-query messages

All systems on the subnet must support the same version. The switch does not automatically detect Version 1 systems and switch to Version 1. Configure the switch for Version 2 if all devices on the subnet support IGMP version 2.

To control which version of IGMP the switch uses, use the following command in configuration mode:

Command	Purpose
ip igmp version {2 1} vlan <1-4093>	Select the IGMP version that the switch uses in a vlan.

Modifying the IGMP Host-Query Message Interval

Multicast switches send IGMP host-query messages to discover which multicast groups are present on attached networks. These messages are sent to the all-systems group address of 224.0.0.1 with a time-to-live (TTL) value of 1.

Multicast switches continue to periodically send host-query messages to refresh their knowledge of memberships present on their networks. If, after some number of queries, the switch software discovers that no local hosts are members of a multicast group, the software stops forwarding onto the local network multicast packets from remote origins for that group and sends a prune message upstream toward the source.

Multicast switches elect a designated switch for the LAN (subnet). The designated switch is the one with the highest IP address. The switch is responsible for sending IGMP host-query messages to all hosts on the LAN. By default, the designated switch sends IGMP host-query messages every 60 seconds in order to keep the IGMP overhead on hosts and networks very low. To modify this interval, use the following command in interface configuration mode:

Command	Purpose
ip igmp query-interval <10-3600	Configure the frequency at which the designated switch sends IGMP
seconds>	host-query messages.

The following example shows setting the IGMP query interval to 200.

Switch(config-if-veth1)#ip igmp query-interval 200

Changing the Maximum Query Response Time

By default, the maximum query response time advertised in IGMP queries is 10 seconds. If the switch is using IGMP Version 2, you can change this value. To change the maximum query response time, use the following command in configuration mode:

Command	Purpose
ip igmp query-max-response-time	Set the maximum query response time advertised in IGMP
<1-25 seconds>	queries.

6.4 Using Access Lists

An access list is a collection of criteria statements that the switch uses to determine whether to allow or block traffic based on IP addresses. Use Access lists to provide basic security on your network, and to prevent unnecessary traffic between network segments by permitting only required traffic onto your network.

57 Asante IntraCore IC36240 User’s Manual