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This module describes the required and optional tasks for configuring Multicast Distributed Switching (MDS).
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Configuring Multicast Distributed Switching" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
•Information About Multicast Distributed Switching
•How to Configure Multicast Distributed Switching
•Configuration Examples for Configuring Multicast Distributed Switching
•Feature Information for Configuring Multicast Distributed Switching
•Advantages of Multicast Distributed Switching
•Multicast Distributed Switching Is Disabled by Default
Prior to MDS, IP multicast traffic was always switched at the Route Processor (RP) in the Route Switch Processor (RSP)-based platforms.
Switching multicast traffic at the RP had the following disadvantages:
•The load on the RP increased. This affected important route updates and calculations (for Border Gateway Protocol (BGP), among others) and could stall the router if the multicast load was substantial.
•The net multicast performance was limited to what a single RP could switch.
MDS solves these problems by performing distributed switching of multicast packets received at the line cards (Versatile Interface Processors [VIPs] in the case of RSP, and line cards in the case of Cisco 12000 series router). The line card is the interface card that houses the VIPs (in the case of RSP) and the line card (in the case of Cisco 12000 series router). MDS is accomplished using a forwarding data structure called a Multicast Forwarding Information Base (MFIB), which is a subset of the routing table. A copy of MFIB runs on each line card and is always kept up to date with the MFIB table of the RP.
MDS can work in conjunction with Cisco Express Forwarding or unicast distributed fast switching (DFS).
Starting with Cisco IOS Release 11.2GS, IP multicast traffic can be distributed switched on RSP-based platforms with VIPs. MDS is the only multicast switching method on the Cisco 12000 series router starting with Cisco IOS Release 11.2(11)GS.
On the Cisco 7500 series router, the default is IP multicast fast switching. MDS is an option that is available and is disabled by default.
On the Cisco 12000 series routers, MDS is also disabled by default. To switch multicast packets on the Cisco 12000 series router, you need to configure all interfaces for MDS. MDS is the only multicast switching mode for the Cisco 12000 series router.
If MDS is not enabled on an incoming interface that is capable of MDS, incoming multicast packets are not distributed switched; the multicast packets are fast switched at the RP. Also, if the incoming interface is not capable of MDS, packets are fast switched or process-switched at the RP.
If MDS is enabled on the incoming interface, but at least one of the outgoing interfaces cannot fast switch, packets are process switched.
Note We recommended that you disable fast switching on any interface when MDS is enabled.
•Configuring Multicast Distributed Switching (required)
•Maintaining Multicast Distributed Switching (optional)
•Monitoring Multicast Distributed Switching (optional)
Perform the following task to configure MDS. To configure MDS, you must enable it globally and on at least one interface because MDS is an attribute of the interface.
1. enable
2. configure terminal
3. ip multicast-routing distributed
4. interface type number
5. ip route-cache distributed
6. ip mroute-cache distributed
7. Repeat Steps 4 through 6 for each interface that you want to perform MDS.
8. end
Note When you enable an interface to perform distributed switching of incoming multicast packets, you are configuring the physical interface, not the logical interface (subinterface). All subinterfaces are included in the physical interface.
•Maintaining Multicast Distributed Switching on the Line Card
•Maintaining Multicast Distributed Switching on the Route Processor
Perform the following task to maintain MDS on the line card.
1. enable
2. clear ip mds forwarding
3. exit
Perform the following task to maintain MDS on the RP.
1. enable
2. clear ip mroute {* | group [source]}
3. clear ip pim interface count
4. exit
•Monitoring Multicast Distributed Switching on the Line Card
•Monitoring Multicast Distributed Switching on the Route Processor
Perform the following task to monitor MDS on the line cards.
Remember that to reach a line card's console, enter the attach slot# command, using the slot number where the line card resides.
Router> attach 1
LC-Slot1> enable
LC-Slot1#
1. enable
2. show ip mds forwarding [group-address]
3. show ip mds summary
4. exit
Step 1 enable
Use this command to enable privileged EXEC mode. Enter a password, if prompted. For example:
Router> enable
Router#
Step 2 show ip mds forwarding [group-address]
Use this command to display the MFIB table, forwarding information, related flags, and counts. For example:
Router# show ip mds forwarding
IP multicast MDFS forwarding information and statistics:
Flags: N - Not MDFS switchable, F - Not all MDFS switchable, O - OIF Null
R - In-ratelimit, A - In-access, M - MTU mismatch, P - Register set
Interface state: Interface, Next-Hop, Mac header
(*, 224.2.170.73),
Incoming interface: Null
Pkts: 0, last used: never, Kbps: 0, fast-flags: N
Outgoing interface list: Null
(192.168.62.86, 224.2.170.73) [31]
Incoming interface: Fddi3/0/0
Pkts: 3034, last used: 00:00:00, Kbps: 0, fast-flags: M
Outgoing interface list:
Step 3 show ip mds summary
Use this command to display a summary of the MFIB. For example:
Router# show ip mds summary
IP multicast MDFS forwarding information and statistics:
Flags: N - Not MDFS switchable, F - Not all MDFS switchable, O - OIF Null
R - In-ratelimit, A - In-access, M - MTU mismatch, P - Register set
Interface state: Interface, Next-Hop, Mac header
(*, 224.2.170.73),
Incoming interface: Null
Pkts: 0, last used: never, Kbps: 0, fast-flags: N
(192.168.62.86, 224.2.170.73) [31]
Incoming interface: Fddi3/0/0
Pkts: 3045, last used: 00:00:03, Kbps: 0, fast-flags: M
(192.168.3.7, 224.2.170.73) [334]
Incoming interface: Fddi3/0/0
Pkts: 0, last used: never, Kbps: 0, fast-flags: M
Step 4 exit
Use this command to exit to user EXEC mode. For example:
Router# exit
Router>
Perform the following task to monitor MDS on the RP.
1. enable
2. show ip mds stats [switching | linecard
3. show mds interface
4. show interface stats
5. exit
Step 1 enable
Use this command to enable privileged EXEC mode. Enter a password, if prompted. For example:
Router> enable
Router#
Step 2 show ip mds stats [switching | linecard]
Use this command to display switching statistics or line card statistics for MDS. This example displays switching statistics:
Router# show ip mds stats switching
Slot Total Switched Drops RPF Punts Failures
(switch/clone)
1 0 0 0 0 4 0/0
3 20260925 18014717 253 93 2247454 1/0
This example displays linecard statistics:
Router# show ip mds linecard
Slot Status IPC(seq/max) Q(high/route) Reloads
1 active 10560/10596 0/0 9
3 active 11055/11091 0/0 9
Step 3 show mds interface
Use this command to display MDS interfaces. For example:
Router# show mds interface
Interface SW-Index HW-Index HW IDB FS Vector VRF
Ethernet1/0/0 2 1 0x60C2DB40 0x602FB7A4 default
Ethernet1/0/1 3 2 0x60C32280 0x603D52B8 default
Ethernet1/0/2 4 3 0x60C35E40 0x602FB7A4 default
Ethernet1/0/3 5 4 0x60C39E60 0x603D52B8 default
Ethernet1/0/4 6 5 0x60C3D780 0x602FB7A4 default
Ethernet1/0/5 7 6 0x60C41140 0x602FB7A4 default
Ethernet1/0/6 8 7 0x60C453A0 0x602FB7A4 default
Ethernet1/0/7 9 8 0x60C48DC0 0x602FB7A4 default
POS2/0/0 10 9 0x0 default
POS3/0/0 11 10 0x0 default
Virtual-Access1 13 11 0x0 default
Loopback0 14 12 0x0 default
Tunnel0 15 23 0x61C2E480 0x603D52B8 vrf1
Tunnel1 16 24 0x61C267E0 0x603D52B8 vrf2
Ethernet1/0/3.1 17 4 0x60C39E60 0x603D52B8 vrf1
Ethernet1/0/3.2 18 4 0x60C39E60 0x603D52B8 vrf2
Step 4 show interface stats
Use this command to display numbers of packet that were process switched, fast switched, and distributed switched. For example:
Router# show interface stats
GigabitEthernet0/0
Switching path Pkts In Chars In Pkts Out Chars Out
Processor 0 0 225 77625
Route cache 0 0 0 0
Multi-Processor Fwding 950 221250 500 57000
Total 950 221250 725 134625
GigabitEthernet0/1
Switching path Pkts In Chars In Pkts Out Chars Out
Processor 1 60 226 77685
Route cache 0 0 0 0
Multi-Processor Fwding 500 57000 500 57000
Total 501 57060 726 134685
GigabitEthernet0/2
Switching path Pkts In Chars In Pkts Out Chars Out
Processor 1 60 226 77685
Route cache 0 0 0 0
Multi-Processor Fwding 0 0 0 0
Total 1 60 226 77685
FastEthernet1/0
Switching path Pkts In Chars In Pkts Out Chars Out
Processor 34015 5331012 1579 158190
Route cache 0 0 0 0
Total 34015 5331012 1579 158190
Step 5 exit
Use this command to exit to user EXEC mode. For example:
Router# exit
Router>
•Example: Configuring Multicast Distributed Switching
•Example: Maintaining Multicast Distributed Switching
The following example show how to enables MDS:
configure terminal
ip multicast-routing distributed
interface pos 1/0/0
ip route-cache distributed
ip mroute-cache distributed
end
The ip route-cache distributed command is needed on the RSP only, not on the GSR.
This section contains the following examples for maintaining MDS:
•Example: Maintaining Multicast Distributed Switching on the Line Card
•Example: Maintaining Multicast Distributed Switching on the Route Processor
The following example shows how to maintain MDS on the line card:
enable
clear ip mds forwarding
exit
In this example, the MFIB table of the line card is cleared of entries and resynchronized with the RP.
The following example shows how to maintain MDS on the RP:
enable
clear ip mroute *
clear ip pim interface count
exit
In this example, all entries are deleted from the IP multicast routing table and all line card counts or packet counts are cleared.
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No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
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No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature. |
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Table 1 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note Table 1 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Cisco Express Forwarding—A Layer 3 switching technology. Cisco Express Forwarding can also refer to central Cisco Express Forwarding mode, one of two modes of Cisco Express Forwarding operation. Cisco Express Forwarding enables a Route Processor (RP) to perform express forwarding. Distributed Cisco Express Forwarding is the other mode of Cisco Express Forwarding operation
line card—A general term for an interface processor that can be used in various Cisco products. For example, a Versatile Interface Processor (VIP) is a line card for the Cisco 7500 series router.
MFIB—Multicast Forwarding Information Base. A protocol-independent multicast forwarding system that contains unique multicast forwarding entries for each source or group pair known in a given network. There is a separate MFIB for every logical network (VPN) in which the router is configured. Each MFIB entry resolves a given source or group pair to an incoming interface (IIF) for reverse forwarding (RPF) checking and an outgoing interface list (olist) for multicast forwarding.
RP—Route Processor. The processor module in the Cisco 7000 series routers that contains the CPU, system software, and most of the memory components that are used in the router. It is sometimes called a supervisory processor.
RSP—Route Switch Processor. Processor module in the Cisco 7000 series routers that integrates the functions of the Route Processor (RP) and the Switch processor (SP).
VIP—Versatile Interface Processor. An interface card used in Cisco 7000 and Cisco 7500 series routers. The VIP provides multilayer switching and runs Cisco IOS.