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This chapter describes how to configure multicast services on the Catalyst 5000 series switches.
This chapter consists of the following sections:
These sections describe how to use the Cisco Group Management Protocol (CGMP) on the
Catalyst 5000 series switches:
These sections describe how CGMP works on the Catalyst 5000 series switches:
CGMP is supported in Catalyst 5000 series supervisor engine software release 2.2 or later on the Catalyst 5000 series switch and Cisco IOS software release 11.1(3) or later on Cisco routers.
CGMP works with Internet Group Management Protocol (IGMP) messages to dynamically configure Catalyst 5000 series switch ports so that IP multicast traffic is forwarded only to those ports associated with IP multicast hosts.
CGMP software components run on both the Cisco router and the Catalyst 5000 series switch. A CGMP-capable IP multicast router sees all IGMP packets and can inform the Catalyst 5000 series switch when specific hosts join or leave IP multicast groups.
When the CGMP-capable router receives an IGMP control packet, it creates a CGMP packet that contains the request type (either join or leave), the multicast group address, and the Media Access Control (MAC) address of the host. The router sends the CGMP packet to a well-known address to which all Catalyst 5000 series switches listen. When a switch receives the CGMP packet, the supervisor engine module interprets the packet and modifies the forwarding table automatically.
You can statically configure multicast groups using the set cam static command. Multicast groups learned through CGMP are dynamic. If you specify group membership for a multicast group address, your static setting supersedes any automatic manipulation by CGMP. Multicast group membership lists can consist of both user-defined and CGMP-learned settings.
If a CGMP-learned port link is disabled for any reason, CGMP removes that port from any multicast group memberships.
We recommend that you enable the spanning-tree PortFast feature on ports to which hosts are directly connected if you are using CGMP. For information on the spanning-tree PortFast feature, see the "Configuring Spanning Tree" chapter.
When a host wants to join an IP multicast group, it sends an IGMP join message specifying its MAC address and the IP multicast group it wants to join. The CGMP-capable router then builds a CGMP join message and multicasts the join message to the well-known address to which the Catalyst 5000 series switches listen.
Upon receipt of the join message, each Catalyst 5000 series switch searches its Enhanced Address Recognition Logic (EARL) table to determine if it contains the MAC address of the host asking to join the multicast group. If a switch finds the MAC address of the host in its EARL table associating the MAC address with a nontrunking port, the switch creates a multicast forwarding entry in the EARL forwarding table. The host associated with that port receives multicast traffic for that multicast group. In this way, the EARL automatically learns the MAC addresses and port numbers of the IP multicast hosts.
The CGMP-capable router sends periodic multicast-group queries. If a host wants to remain in a multicast group, it responds to the query from the router. In this case, the router does nothing. If a host does not want to remain in the multicast group, it does not respond to the router query. If after a number of queries the router receives no reports from any host in a multicast group, the router sends a CGMP command to the Catalyst 5000 series switch, telling it to remove the multicast group from its forwarding tables.
CGMP fast-leave-processing allows the Catalyst 5000 series supervisor engine module to detect IGMP V.2 leave messages sent to the all-routers multicast address by hosts on any of the supervisor engine module ports. When the supervisor engine module receives a leave message, it starts a query-response timer. If this timer expires before a CGMP join message is received, the port is pruned from the multicast tree for the multicast group specified in the original leave message. Fast-leave processing ensures optimal bandwidth management for all hosts on a switched network, even when multiple multicast groups are in use simultaneously.
These guidelines apply when configuring CGMP on the Catalyst 5000 series switches:
These sections describe how to configure CGMP on the Catalyst 5000 series switches:
To enable CGMP, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Enable CGMP on the switch. | set cgmp enable |
Step 2 Verify that CGMP is enabled. | show cgmp statistics [vlan_num] |
This example shows how to enable CGMP and verify the configuration (shown by the arrow):
Console> (enable) set cgmp enable
CGMP support for IP multicast enabled. Console> (enable) show cgmp statistics 1
CGMP enabled CGMP statistics for vlan 1: valid rx pkts received 211915 invalid rx pkts received 0 valid cgmp joins received 211729 valid cgmp leaves received 186 valid igmp leaves received 0 valid igmp queries received 3122 igmp gs queries transmitted 0 igmp leaves transmitted 0 failures to add GDA to EARL 0 topology notifications received 80 number of CGMP packets dropped 2032227 Console> (enable)
When you enable CGMP, the switch automatically learns to which ports a multicast router is connected.
To statically define multicast router ports, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Configure multicast router ports. | set multicast router mod_num/port_num |
Step 2 Verify the multicast router configuration. | show multicast router [mod_num/port_num] [vlan_id] |
Step 3 Verify the multicast router information that was learned dynamically via CGMP. | show multicast router cgmp [mod_num/port_num] [vlan_id] |
This example shows how to define a multicast router port manually and verify the configuration (the asterisk [*] next to the multicast router on port 3/1 indicates that the entry was configured manually):
Console> (enable) set multicast router 3/1
Port 3/1 added to multicast router port list.
Console> (enable) show multicast router
CGMP enabled IGMP disabled Port Vlan --------- ---------------- 2/1 99 2/2 255 3/1 * 1 7/9 2,99 Total Number of Entries = 4 '*' - Configured Console> (enable)
This example shows how to display only those multicast router ports that were learned dynamically via CGMP:
Console> (enable) show multicast router cgmp
CGMP enabled IGMP disabled Port Vlan --------- ---------------- 2/1 99 2/2 255 7/9 2,99 Total Number of Entries = 3 '*' - Configured Console> (enable)
To statically configure a multicast group, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Add one or more multicast MAC addresses to the CAM table. | set cam {static | permanent} multicast_mac mod_num/port_num [vlan] |
Step 2 Verify the multicast group configuration. | show multicast group [mac_addr] [vlan_id] |
Step 3 Verify the multicast group information that was learned dynamically via CGMP. | show multicast group cgmp [mac_addr] [vlan_id] |
Step 4 If desired, show the total number of multicast addresses (groups) in a VLAN. | show multicast group count [cgmp] [vlan_id] |
This example shows how to define multicast groups manually and verify the configuration (the asterisks indicate the entry was manually configured):
Console> (enable) set cam static 01-00-11-22-33-44 2/6-12
Static multicast entry added to CAM table. Console> (enable) set cam static 01-11-22-33-44-55 2/6-12
Static multicast entry added to CAM table. Console> (enable) set cam static 01-22-33-44-55-66 2/6-12
Static multicast entry added to CAM table. Console> (enable) set cam static 01-33-44-55-66-77 2/6-12
Static multicast entry added to CAM table. Console> (enable) show multicast group
CGMP enabled IGMP disabled VLAN Dest MAC/Route Des Destination Ports or VCs / [Protocol Type] ---- ------------------ ---------------------------------------------------- 1 01-00-11-22-33-44* 2/6-12 1 01-11-22-33-44-55* 2/6-12 1 01-22-33-44-55-66* 2/6-12 1 01-33-44-55-66-77* 2/6-12 Total Number of Entries = 4 Console> (enable)
To enable CGMP leave processing, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Enable CGMP leave processing on a device. | set cgmp leave enable |
Step 2 Verify that CGMP leave processing is enabled. | show cgmp leave |
This example shows how to enable CGMP leave processing and verify the configuration:
Console> (enable) set cgmp leave enable
CGMP leave processing enabled. Console> (enable) Console> (enable) show cgmp leave
CGMP: enabled CGMP leave: enabled Console> (enable)
To check CGMP statistics on the switch, perform this task:
Display CGMP statistics. | show cgmp statistics [vlan_id] |
This example shows how to display CGMP statistics:
Console> (enable) show cgmp statistics
CGMP enabled CGMP statistics for vlan 1: valid rx pkts received 211915 invalid rx pkts received 0 valid cgmp joins received 211729 valid cgmp leaves received 186 valid igmp leaves received 0 valid igmp queries received 3122 igmp gs queries transmitted 0 igmp leaves transmitted 0 failures to add GDA to EARL 0 topology notifications received 80 number of CGMP packets dropped 2032227 Console> (enable)
To clear manually configured multicast router ports, perform one of these tasks in privileged mode:
| Task | Command |
|---|---|
| clear multicast router mod_num/port_num |
| clear multicast router all |
This example shows how to clear a manually configured multicast router port entry:
Console> (enable) clear multicast router 2/12
Port 2/12 cleared from multicast router port list. Console> (enable)
To disable manually configured multicast group entries, perform this task in privileged mode:
| Task | Command |
|---|---|
Clear a multicast group entry from the CAM table. | clear cam mac_addr [vlan] |
This example shows how to clear a multicast group entry from the CAM table:
Console> (enable) clear cam 01-11-22-33-44-55 1
CAM entry cleared. Console> (enable)
To disable CGMP leave processing, perform this task in privileged mode:
| Task | Command |
|---|---|
Disable CGMP leave processing on a device. | set cgmp leave disable |
This example shows how to disable CGMP leave processing on the switch:
Console> (enable) set cgmp leave disable
CGMP leave processing disabled. Console> (enable)
To disable CGMP on the switch, perform this task in privileged mode:
| Task | Command |
|---|---|
Disable CGMP on the switch. | set cgmp disable |
This example shows how to disable CGMP:
Console> (enable) set cgmp disable
CGMP support for IP multicast disabled. Console> (enable)
Internet Group Management Protocol (IGMP) snooping allows Catalyst 5000 series switches to examine IGMP packets and make forwarding decisions based on their content.
These sections describe how to use IGMP snooping on the Catalyst 5000 series switches:
These guidelines apply when you are configuring IGMP snooping on the Catalyst 5000 series switches:
These sections describe how to configure IGMP on the Catalyst 5000 series switches:
To enable IGMP snooping, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Enable IGMP snooping on the switch. | set igmp enable |
Step 2 Verify that IGMP snooping is enabled. | show igmp statistics [vlan_num] |
This example shows how to enable IGMP snooping and verify the configuration (shown by the arrow):
Console> (enable) set igmp enable
IGMP Snooping is enabled. CGMP is disabled. Console> (enable) show igmp statistics
When you enable IGMP snooping, the switch automatically learns to which ports a multicast router is connected.
To statically define multicast router ports, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Configure multicast router ports. | set multicast router mod_num/port_num |
Step 2 Verify the multicast router configuration. | show multicast router [mod_num/port_num] [vlan_id] |
Step 3 Verify the multicast router information that was learned dynamically via IGMP. | show multicast router igmp [mod_num/port_num] [vlan_id] |
This example shows how to define a multicast router port manually and verify the configuration (the asterisk [*] next to the multicast router on port 5/7 indicates that the entry was configured manually):
Console> (enable) set multicast router 5/7
Port 5/7 added to multicast router port list.
Console> (enable) show multicast router
CGMP disabled IGMP enabled Port Vlan --------- ---------------- 1/1 1 2/1 2,99,255 5/7 * 99 Total Number of Entries = 3 '*' - Configured Console> (enable)
This example shows how to display only those multicast router ports that were learned dynamically via IGMP:
Console> (enable) show multicast router igmp
CGMP disabled IGMP enabled Port Vlan --------- ---------------- 1/1 1 2/1 2,99,255 Total Number of Entries = 2 '*' - Configured Console> (enable)
To statically configure a multicast group, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Add one or more multicast MAC addresses to the CAM table. | set cam {static | permanent} multicast_mac mod_num/port_num [vlan] |
Step 2 Verify the multicast group configuration. | show multicast group [mac_addr] [vlan_id] |
Step 3 Verify the multicast group information that was learned dynamically via IGMP. | show multicast group igmp [mac_addr] [vlan_id] |
Step 4 If desired, show the total number of multicast addresses (groups) in a VLAN. | show multicast group count [igmp] [vlan_id] |
This example shows how to define multicast groups manually and verify the configuration:
Console> (enable) set cam static 01-00-11-22-33-44 2/6-12
Static multicast entry added to CAM table. Console> (enable) set cam static 01-11-22-33-44-55 2/6-12
Static multicast entry added to CAM table. Console> (enable) set cam static 01-22-33-44-55-66 2/6-12
Static multicast entry added to CAM table. Console> (enable) set cam static 01-33-44-55-66-77 2/6-12
Static multicast entry added to CAM table. Console> (enable) show multicast group
CGMP disabled IGMP enabled VLAN Dest MAC/Route Des Destination Ports or VCs / [Protocol Type] ---- ------------------ ---------------------------------------------------- 1 01-00-11-22-33-44* 2/6-12 1 01-11-22-33-44-55* 2/6-12 1 01-22-33-44-55-66* 2/6-12 1 01-33-44-55-66-77* 2/6-12 Total Number of Entries = 4 Console> (enable)
To check IGMP snooping statistics on the switch, perform this task:
| Task | Command |
|---|---|
Display IGMP snooping statistics. | show igmp statistics [vlan_id] |
This example shows how to display IGMP snooping statistics:
Console> (enable) show igmp statistics
IGMP enabled IGMP statistics for vlan 1: Total valid pkts rcvd: 18951 Total invalid pkts recvd 0 General Queries recvd 377 Group Specific Queries recvd 0 MAC-Based General Queries recvd 0 Leaves recvd 14 Reports recvd 16741 Queries Xmitted 0 GS Queries Xmitted 16 Reports Xmitted 0 Leaves Xmitted 0 Failures to add GDA to EARL 0 Topology Notifications rcvd 10 IGMP packets dropped 0 Console> (enable)
The Catalyst 5000 series switch dynamically chooses either IGMP-only or IGMP/CGMP mode, depending on the traffic present on the network. IGMP-only mode is used in networks with no CGMP devices. IGMP/CGMP mode is used in networks with both IGMP and CGMP devices.
To check the IGMP/CGMP mode on the switch, perform this task:
| Task | Command |
|---|---|
Show the IGMP/CGMP mode. | show igmp mode |
To clear manually configured multicast router ports, perform one of these tasks in privileged mode:
| Task | Command |
|---|---|
| clear multicast router mod_num/port_num |
| clear multicast router all |
This example shows how to clear a manually configured multicast router port entry:
Console> (enable) clear multicast router 2/12
Port 2/12 cleared from multicast router port list. Console> (enable)
To disable manually configured multicast group entries, perform this task in privileged mode:
| Task | Command |
|---|---|
Clear a multicast group entry from the CAM table. | clear cam mac_addr [vlan] |
This example shows how to clear a multicast group entry from the CAM table:
Console> (enable) clear cam 01-11-22-33-44-55 1
CAM entry cleared. Console> (enable)
To disable IGMP snooping on the switch, perform this task in privileged mode:
| Task | Command |
|---|---|
Disable IGMP snooping on the switch. | set igmp disable |
This example shows how to disable IGMP snooping:
Console> (enable) set igmp disable
IGMP feature for IP multicast disabled Console> (enable)
These sections describe how to use broadcast/multicast suppression on the Catalyst 5000 series switches:
These sections describe how broadcast/multicast suppression works on the Catalyst 5000 series switches:
Broadcast/multicast suppression prevents switched ports on a LAN from being disrupted by a broadcast storm on one of the ports. A LAN broadcast storm occurs when broadcast or multicast packets flood the LAN, creating excessive traffic and degrading network performance. Errors in the protocol-stack implementation or in the network configuration can cause a broadcast storm.
Broadcast/multicast suppression works by measuring broadcast/multicast activity on a LAN. Broadcast/multicast activity can be measured in two ways:
Since packet sizes vary, bandwidth-based measurement is more accurate and effective than packet-based measurement.
Broadcast/multicast suppression uses filtering that measures broadcast/multicast activity on a LAN over a one-second time period and compares the measurement with a predefined threshold. If the threshold is reached, further broadcast activity is suppressed for the duration of a specified time period. Broadcast/multicast suppression is disabled by default.
Figure 17-1 shows the broadcast/multicast traffic patterns on a port over a given period of time. In this example, broadcast/multicast suppression occurs between time intervals T1 and T2 and between T4 and T5. During those time periods, the amount of broadcast/multicast traffic exceeded the configured threshold.
The broadcast suppression threshold numbers and the time interval combination make the broadcast/multicast suppression algorithm work with different levels of granularity. A higher threshold allows more broadcast/multicast packets to pass through.
Broadcast/multicast suppression on the Catalyst 5000 series switches is implemented either in hardware or in software. Hardware broadcast/multicast suppression uses the bandwidth-based method. Software broadcast/multicast suppression uses the packet-based method.
Hardware broadcast/multicast suppression circuitry in Catalyst 5000 series switches monitors packets passing from a port to the Catalyst 5000 switching bus. Using the Individual/Group bit in the packet destination address, the broadcast/multicast suppression circuitry determines if the packet is a unicast or a broadcast/multicast. It keeps track of the current count of broadcasts/multicasts within the one-second time interval, and when a threshold is reached, filters out subsequent broadcast/multicast packets.
Since hardware broadcast/multicast suppression uses a bandwidth-based method to measure broadcast/multicast activity, the most significant implementation factor is setting the percentage of total available bandwidth that can be used by broadcast/multicast traffic. A threshold value of 100 percent means that no limit is placed on broadcast traffic. Using the set port broadcast command, you can set up the broadcast suppression threshold value.
Since packets do not arrive at uniform intervals, the one-second time interval during which broadcast/multicast activity is measured can affect the behavior of broadcast/multicast suppression.
These Catalyst 5000 series switching modules support hardware broadcast/multicast suppression:
Software broadcast/multicast suppression is supported in all Ethernet modules that support hardware broadcast/multicast suppression (see the section "Hardware (Bandwidth-Based) Broadcast/Multicast Suppression"); it is not available for use with ATM or FDDI cards.
Since software broadcast/multicast suppression uses a packet-based method to measure broadcast/multicast activity, the most significant implementation factor is setting a threshold value for the number of broadcast packets-per-second allowed. If you set the threshold number to 0 packets per second, no broadcast/multicast packets are suppressed.
These sections describe how to configure broadcast/multicast suppression on the Catalyst 5000 series switches:
To enable bandwidth-based broadcast/multicast suppression, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Specify the broadcast/multicast suppression threshold for one or more ports as a percentage of total bandwidth. | set port broadcast mod_num/port_num threshold% |
Step 2 Verify the broadcast/multicast suppression configuration. | show port broadcast [mod_num[/port_num]] |
This example shows how to enable bandwidth-based broadcast/multicast suppression and verify the configuration:
Console> (enable) set port broadcast 3/1 75%
Port(s) 3/1-24 broadcast traffic limited to 75%. Console> (enable) show port broadcast 3
Port Broadcast-Limit Broadcast-Drop -------- --------------- -------------- 3/1-8 75 % - 3/9-16 75 % - 3/17-24 75 % - Console> (enable)
To enable packet-based broadcast/multicast suppression, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Specify the broadcast/multicast suppression threshold for one or more ports as a maximum number of broadcast or multicast packets allowed in a one-second period. | set port broadcast mod_num/port_num threshold |
Step 2 Verify the broadcast/multicast suppression configuration. | show port broadcast [mod_num[/port_num]] |
This example shows how to enable packet-based broadcast/multicast suppression and verify the configuration:
Console> (enable) set port broadcast 2/6 500
Port(s) 2/6 broadcast traffic limited to 500 packets/second. Console> (enable) set port broadcast 2/7 500
Port(s) 2/7 broadcast traffic limited to 500 packets/second. Console> (enable) set port broadcast 2/8 500
Port(s) 2/8 broadcast traffic limited to 500 packets/second. Console> (enable) show port broadcast
Port Broadcast-Limit Broadcast-Drop -------- --------------- -------------- 1/1 - - 1/2 - - 2/1 - 0 2/2 - 0 2/3 - 0 2/4 - 0 2/5 - 0 2/6 500 p/s 0 2/7 500 p/s 0 2/8 500 p/s 0 2/9 - 0 2/10 - 0 2/11 - 0 2/12 - 0 Console> (enable)
To disable broadcast/multicast suppression on one or more ports, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Disable broadcast/multicast suppression on one or more ports. | clear port broadcast mod_num/port_num |
Step 2 Verify the broadcast/multicast suppression configuration. | show port broadcast |
This example shows how to disable broadcast/multicast suppression on one or more ports:
Console> (enable) clear port broadcast 3/1
Port 3/1-8 broadcast traffic unlimited. Console> (enable)
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