To enable IPv4 Multicast routing on all IP-enabled interfaces of the router and to enable Multicast forwarding, use the ip multicast-routing command in global configuration mode. To stop Multicast routing and forwarding, use the no form of this command.

Syntax

ip multicast-routing igmp-proxy

no ip multicast-routing

Parameters

• igmp-proxy—Enable Multicast routing using IGMP Proxy.

Default Configuration

Multicast routing is not enabled.

Command Mode

Global Configuration mode

User Guidelines

Use the ip multicast-routing command with parameter to specify the needed IP Multicast Routing Protocol.

To forward IPv4 Multicast packets on an interface, IPv4 Multicast forwarding must be enabled globally and an IPMv4 Routing protocol must be enabled on the interface.

Example

The following example enables IP Multicast routing using IGMP Proxy:

switchxxxxxx(config)# ip multicast-routing igmp-proxy

To configure the time-to-live (TTL) threshold of packets being forwarded out an interface, use the ip multicast ttl-threshold command in Interface Configuration mode. To return to the default TTL threshold, use the no form of this command.

Syntax

ip multicast ttl-threshold ttl-value

no ip multicast ttl-threshold

Parameters

• ttl-value—Time-to-live value, in hops. It can be a value from 0 to 256.

Default Configuration

The default TTL value is 0.

Command Mode

Interface Configuration mode

User Guidelines

Multicast packets with a TTL value less than the threshold will not be forwarded on the interface. The default value of 0 means all Multicast packets are forwarded on the interface.

A value of 256 means that no Multicast packets are forwarded on the interface.

You should configure the TTL threshold only on border routers. Conversely, routers on which you configure a TTL threshold value automatically become border routers.

Example

The following example sets the TTL threshold on a border router to 200:

switchxxxxxx(config)# interface vlan 100
switchxxxxxx(config-if)# ip multicast ttl-threshold 200
switchxxxxxx(config-if)# exit

To display the contents of the Multicast routing (mroute) table, use the show ip mroute command in user EXEC or privileged EXEC mode.

Syntax

show ip mroute [group-address [source-address]] [summary]

Parameters

• group-address—Destination Multicast IP address.

• source-address—Source IP address.

• summary—Filters the output to display a one-line, abbreviated summary of each entry in the mroute table.

Command Mode

User EXEC mode

Privileged EXEC mode

User Guidelines

Use the show ip mroute command to display information about Mroute entries in the mroute table. The switch populates the Multicast routing table by creating (S, G) entries from (*, G) entries. The asterisk (*) refers to all source addresses, the “S” refers to a single source address, and the “G” is the destination Multicast group address. In creating (S, G) entries, the switch uses the best path to that destination group found in the Unicast routing table (that is, through Reverse Path Forwarding [RPF]).

Examples

Description of Significant fields in the examples below

Timers:Uptime/Expires—“Uptime” indicates per interface how long (in hours, minutes, and seconds) the entry has been in the IP Multicast routing table. “Expires” indicates per interface how long (in hours, minutes, and seconds) until the entry will be removed from the IP Multicast routing table.

(*, 224.0.255.1) and (192.168.37.100/32, 224.0.255.1)—Entry in the IP Multicast routing table. The entry consists of the IP address of the source router followed by the IP address of the Multicast group. An asterisk (*) in place of the source router indicates all sources.

Entries in the first format are referred to as (*, G) or “star comma G” entries. Entries in the second format are referred to as (S, G) or “S comma G” entries. (*, G) entries are used to build (S, G) entries.

Incoming interface: —Expected interface for a Multicast packet from the source. If the packet is not received on this interface, it is discarded.

Outgoing Interface List (OIF):—Interfaces through which packets will be forwarded.

Example 1. The following is sample output from the show ip mroute command with the summary keyword:

switchxxxxxx# show ip mroute summary
Timers: Uptime/Expires
IP Multicast Routing Table
(172.16.160.67/32, 224.2.127.254), 00:02:46/00:00:12, OIF count:2
(172.16.244.217/32, 224.2.127.254), 00:02:15/00:00:40, OIF count:
(172.16.8.33/32, 224.2.127.254), 00:00:25/00:02:32, OIF count:2
(172.16.2.62/32, 224.2.127.254), 00:00:51/00:02:03, OIF count:2
(172.16.8.3/32, 224.2.127.254), 00:00:26/00:02:33, OIF count:2
(172.16.60.189/32, 224.2.127.254), 00:03:47/00:00:46, OIF count:2

Example 2. The following is sample output from the show ip mroute command:

switchxxxxxx# show ip mroute
Timers: Uptime/Expires
IP Multicast Routing Table
(*, 224.0.255.3), 5:29:15/00:03:01
Incoming interface: vlan2
Outgoing interface list:
vlan100, 5:29:15/0:02:57
(192.168.46.0/24, 224.0.255.3), 05:29:15/00:02:59
Incoming interface: vlan2
Outgoing interface list:
vlan5, 05:29:15/00:02:57

To display general information about IP Multicast configuration, use the show ip multicast command in user EXEC or privileged EXEC mode.

Syntax

show ip multicast [interface interface-id]

Parameters

• interface—Displays IP Multicast-related information about an interface configured for IP Multicast.

• interface-id—Interface identifier for which to display IP Multicast information.

Command Mode

User EXEC mode

Privileged EXEC mode

User Guidelines

Use the show ip multicast command without the interface keyword to display general information about the state of IP Multicast on the router.

Use the show ip multicast command with the interface keyword to display the IP Multicast information about the specified interface.