- Preface
-
- Configuring the Cisco Application Control Engine
- Configuring the Cisco TelePresence Multipoint Switch
- Configuring the Cisco Router with IVR
- Configuring Cisco Unified Communications Manager
- Configuring Cisco TelePresence Manager
- Configuring Cisco Session Border Controllers
- Configuring Cisco TelePresence MSE 8000 Series
- Configuring Internet Group Management Protocol for Multicast Support
- Glossary
Configuring Internet Group Management Protocol for Multicast Support
The following sections describe how to enable Internet Group Management Protocol (IGMP) snooping and the IGMP querier function on the Cisco Catalyst 6500 Series and Cisco Catalyst 4948 Switches that connect to the Cisco TelePresence Exchange System call engines, in this configuration, multicasting between the two call engines.
Additionally, the chapter provides multicast configuration recommendations for non-Cisco switches, and includes the following topics:
•Configuring the IGMP Querier Functionality on a Cisco Switch
•Configuring PIM on a Cisco Router
•Configuring IGMP on a Non-Cisco Switch
Multicasting Overview
The Cisco TelePresence Exchange System employs multicasting to replicate call states between call engine servers in a Cisco TelePresence Exchange System cluster. Therefore, the call engines must be on the same VLAN and subnet.
Note Some of the multicast traffic has a fixed TTL value of 1, which prevents the multicast traffic from being forwarded over multiple layer 3 hops.
Network interface cards (NICs) on end-stations (server or host machine) generally handle multicast traffic. To limit interrupts and congestion on end-stations that do no want to receive multicast traffic, switches can implement IGMP snooping. IGMP snooping allows a switch to learn which end-stations (in this case, the call engines) on the same VLAN want to receive the multicast traffic, and then forward traffic only to those end-station ports that sent IGMP reports and joins for specific groups. The switch then forwards the reports to multicast router (mrouter) ports.
By default, IGMP snooping is enabled on all Cisco switches.
IGMP Querier
You must enable the IGMP querier function to support IGMP snooping on a VLAN in which protocol independent multicast (PIM) is not active.
In a network where IP multicast routing is configured, the IP multicast router acts as the IGMP querier. If the IP multicast traffic in a VLAN only needs to be layer 2 switched, an IP multicast router is not required. Without an IP multicast router on the VLAN, you must configure the Cisco Catalyst 6500 Series and Cisco Catalyst 4948 Switches to act as the IGMP querier so that the switch can send queries.
When enabled, the IGMP querier switch sends out periodic IGMPv3 (for the Cisco Catalyst 6500) or IGMPv2 (for the Cisco Catalyst 4948) queries that trigger IGMP report messages from the end-stations (call engines). IGMP snooping listens to these IGMP reports and discovers the multicast groups that each port wishes to receive data. The switch then builds the MAC address table to allow forwarding of the traffic.
Note the following details on the Cisco implementation of the IGMP snooping querier function:
•IGMP querier must be configured on one switch within the VLAN in which the Cisco TelePresence Exchange System call engines operate. However, if the switch fails or disconnects from the VLAN, there might be an outage.
•When IGMP querier is enabled on one switch within the VLAN, it is possible for switches that do not support IGMP querier to operate within that same VLAN.
•IGMP snooping querier supports IGMP version 2 and 3.
•When enabled, the IGMP snooping querier does not start if it detects IGMP traffic from a multicast router.
•When enabled, the IGMP snooping querier starts after 60 seconds with no IGMP traffic detected from a multicast router.
•When enabled, the IGMP snooping querier disables itself if it detects IGMP traffic from a multicast router.
•When IGMP snooping is enabled, QoS does not support IGMP packets.
Note The IGMP querier feature is not supported on all switches and all platforms, therefore IGMP querier might not work for all environments. In this case, you can enable the querier function on a Cisco router. For more details, see the "Configuring PIM on a Cisco Router" section.
Configuring the IGMP Querier Functionality on a Cisco Switch
Before You Begin
Ensure that IGMP snooping is enabled on the Cisco Catalyst 6500 Series Switch or Cisco Catalyst 4948 Switch.
Configure a switch within the VLAN with a source address to which the IGMP querier function can forward the queries. The IP address does not need to be the default gateway.
Procedure
To configure the IGMP querier function on a Cisco Catalyst 6500 Series Switch, do the following procedure:
Note IP addresses shown in the configurations are for example purposes only.
The following example defines an IGMP query source address within VLAN 630, and enables and verifies the IGMP querier function on the VLAN:
Router# interface vlan 630
Router(config-if)# ip address 10.22.143.241 255.255.255.248
Router(config-if)# igmp snooping querier
Router(config-if)# end
Router# show ip igmp interface vlan 630 | include querier
IGMP snooping fast-leave (for v2) is disabled and querier is enabled
Router#
Procedure
To configure the IGMP querier function on a Cisco Catalyst 4948 Switch, do the following procedure:
The following example defines an IGMP query source address within VLAN 585, and enables and verifies the IGMP querier function on the VLAN:
Router# interface vlan 585
Router(config-if)# ip address 10.22.142.242 255.255.255.224
Router(config-if)# exit
Router(config)# ip igmp snooping querier
Router(config)# no ip igmp snooping vlan 1 querier
Router(config)# ip igmp snooping vlan 585 querier address 10.22.142.242
Router# show ip igmp interface vlan 585
Vlan585 is up, line protocol is up
Internet address is 10.22.142.242/29
IGMP is disabled on interface
Multicast routing is disabled on interface
Multicast TTL threshold is 0
No multicast groups joined by this system
IGMP snooping is globally enabled
IGMP snooping CGMP-AutoDetect is globally enabled
IGMP snooping is enabled on this interface
IGMP snooping fast-leave (for v2) is disabled
IGMP snooping querier is enabled. Querier is 10.22.143.241 (this system)
IGMP snooping explicit-tracking is enabled
IGMP snooping last member query response interval is 1000 ms
IGMP snooping report-suppression is enabled
Configuring PIM on a Cisco Router
You can configure PIM on Cisco IOS-based routers as well as switches that support layer 3 multicast routing (such as the Cisco Catalyst 6500 Series) to allow the router to operate as the IGMP querier, when IGMP querier is not supported on switches within the network.
Note IGMPv2 is the default version for Cisco routers. If IGMPv3 is required in the network, you must specify that version when configuring PIM on the router.
For details on the versions of IGMP support by platform and software version, see the Cisco Feature Navigator at http://www.cisco.com/go/fn.
For redundancy, Cisco recommends that you configure two routers with PIM functionality on the VLAN in which the Cisco TelePresence Exchange System call engines operate.
Cisco recommends that you reference the appropriate Cisco router configuration guide on Cisco.com to ensure that all elements of multicasting (such as multicast forwarding, multicast boundaries and rendezvous point, which is only supported on PIM sparse mode) are properly configured for the router.
Before You Begin
Enable IGMP on the switches within the network.
Procedure
To configure PIM on a Cisco router, do the following procedure:
The following example enables PIM as an IGMP querier function for a router on the VLAN 630:
Router (config)# ip multicast-routing
Router (config)# interface vlan 630
Router(config-if)# ip address 10.22.143.241 255.255.255.248
Router(config-if)# ip pim sparse-mode
Router(config-if)# ip igmp version 3
Router(config-if)# end
Router(config)# show ip pim snooping vlan 630
3 neighbors (0 DR priority incapable, 0 Bi-dir incapable)
6 mroutes, 3 mac entries
DR is 10.10.10.4
RP DF Set
Configuring IGMP on a Non-Cisco Switch
The Cisco TelePresence Exchange Systems use IGMP version 2/3 to join (*,G) multicast groups. Membership queries must be sent in order to maintain awareness of active receivers. Active receivers do not normally send IGMP join/reports in an unsolicited fashion; instead, they send a join at application start and when queried (IGMP RFC3376 section 4.1).
The Cisco TelePresence Exchange System call engine servers do not require or support multicast over multiple layer 3 hops. Therefore, multicasts occur within the VLAN. All switches that are between or directly connected to call engines must support multicast traffic without the need to see IGMP join/reports. However, because IGMP snooping specifically requires information on IGMP join/reports, a switch or router must act as a IGMP query router.
When you are configuring IGMP on a non-Cisco switch that connects to the Cisco TelePresence Exchange System call engine, note the configuration guidelines listed below:
•If the switch is multicast-aware and supports IGMP snooping and IGMP querier, do the following tasks:
–Enable IGMP on the switch if it is not already active.
–Configure the IGMP querier capability on the switch within the VLAN that the call engines operate.
•If the switch is not multicast-aware and does not support IGMP snooping or other multicast protocol, do the following task:
–Cisco recommends placing the call engines in a dedicated VLAN to limit the multicast broadcasts that are addressed to the call engines from being broadcast to other hosts. This ensures that flooded multicast traffic in the broadcast domain will be limited to those hosts that need to receive the multicast traffic.
•If the switch does not support the IGMP querier function, but does support disabling IGMP snooping, then disable IGMP snooping on the switch.
–When you disable IGMP snooping, the multicast traffic is flooded to all hosts in the VLAN. For this reason, Cisco recommends placing the call engines in a dedicated VLAN in order to limit the multicast flooding to those hosts that need to receive the multicast traffic.
•If the switch does not support the IGMP querier function, and does not allow disabling of IGMP snooping, then configure a router interface in the call engine VLAN with PIM sparse-mode.
–Additionally, configure the router to block forwarding of multicast traffic over layer 3 hops.