Protocol Independent Multicast - Dense Mode (PIM-DM)
Protocol Independent Multicast - Dense Mode (PIM-DM) Overview
The PIM-DM protocol can be considered the follow-on to the DVMRP protocol. It is a "flood-and-prune" protocol. Multicast data from a source addressed to a multicast group is "flooded" to all parts of the network. Last-hop routers that detect no member of the destination group "prune" back towards the source. This type of multicast tends to be more efficient when receivers are "densely" distributed throughout the network.
The biggest difference between PIM-DM and DVMRP is that PIM-DM is only a multicast tree-building protocol whereas DVMRP is both a tree-building protocol and a network topology protocol. PIM-DM requires a unicast protocol such as OSPF to be running in the network in order to establish the underlying unicast topology.
PIM-DM namely differs from PIM-SM in that PIM-SM is an "explicit-join" protocol. An "explicit-join" grows branches of the multicast distribution trees from receivers back towards the root of the tree. In this way, multicast traffic only ever flows to members of the group. PIM-DM also differs from PIM-SM in that in PIM-DM all distribution trees are rooted at the sender. PIM-DM has no notion of shared trees, Rendezvous-Points (RPs), (*,G) state, and so on.
Note: PIM uses routes in the multicast Routing Information Base (RIB) to perform its RPF check. By default none of the IGPs (OSPF, RIP) place routes into the multicast RIB. They must be configured to do so. Check the relevant protocol's configuration section in order to obtain the correct syntax.
ip pim dense-mode
Name
ip pim dense-mode - enables PIM dense mode on an interface
Syntax
ip pim dense-mode
no ip pim dense-mode
Mode
Interface Configuration
Parameters
none
Description
The ip pim dense-mode command enables PIM dense mode on the associated interface.
Default
PIM dense mode is disabled by default.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the PIM dense mode protocol on interface fxp0.
(config)# interface fxp0
(config-if)# ip pim dense-mode
ip pim graft-retry-interval
Name
ip pim graft-retry-interval - specifies the value to use for the Retry Interval for sending Graft messages if a Graft acknowledgement has not been received
Syntax
ip pim graft-retry-interval time-seconds
no ip pim graft-retry-interval time-seconds?
Mode
Interface Configuration
Parameters
time-seconds - specifies an integer between 1 and 65535, inclusive, for the number of seconds
Description
The ip pim graft-retry-interval command specifies the value to use for the Retry Interval for sending Graft messages if a Graft Acknowledgement has not been received. The negative form of this command, no ip pim graft-retry-interval, removes the configured time-seconds value and returns it to its default. Note: Specifying a value for time-seconds in the no form has not effect on the configuration. Thus, it is displayed above as optional.
Default
If ip pim graft-retry-interval is not specified, it is the same as if the user had specified the following:
(config-if)# ip pim graft-retry-interval 3
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures a graft retry interval of 10 seconds for interface fxp0.
(config)# interface fxp0
(config-if)# ip pim dense mode
(config-if)# ip pim graft-retry-interval 10
(config-if)# exit
ip pim require-genid
Name
ip pim require-genid - specifies whether to reject packets without a generation ID
Syntax
ip pim require-genid
no ip pim require-genid
Mode
Interface Configuration
Parameters
none
Description
Use the ip pim require-genid command to specify that Advanced Routing Suite should reject packets without the generation ID hello option. The negative form of this command, no ip pim require-genid, specifies that Advanced Routing Suite will allow such packets.
Default
Advanced Routing Suite accepts packets without a generation ID by default. Therefore, if ip pim require-genid is not specified, it is the same as if the user had specified the following:
(config-if)# no ip pim require-genid
Command History
NGC 2.2 - This command was introduced.
Example
The following example specifies that Advanced Routing Suite should reject packets that do not have a generation ID.
(config)# interface fxp1
(config-if)# ip pim dense-mode
(config-if)# ip pim require-genid
(config-if)# exit
(config)#
ip pim source-lifetime
Name
ip pim source-lifetime - specifies the interval during which a directly attached router will continue to send State Refresh messages in the absence of additional multicast data
Syntax
ip pim source-lifetime time-seconds
no ip pim source-lifetime time-seconds?
Mode
Global Configuration
Parameters
time-seconds - the time in seconds, specified as a non-negative integer between 4 and 32766, inclusive
Description
The ip pim source-lifetime command specifies the interval during which a directly attached router will continue to send State Refresh messages in the absence of additional multicast data.
The negative form of this command, no ip pim source-lifetime, removes the configured value and returns this to its default value of 210 seconds. Note: Specifying a value for time-seconds in the no form of this command has no effect on the configuration. Thus, it is displayed above as optional.
Default
If ip pim source-lifetime is not specified, it is the same as if the user had specified the following:
(config)# ip pim source-lifetime 210
Command History
NGC 2.2 - This command was introduced.
NGC 2.3 - The lower limit of this command changed from 1 to 4.
Examples
The following example configures a source lifetime of 150 seconds.
(config)# ip pim source-lifetime 150
ip pim state-refresh-capable
Name
ip pim state-refresh-capable - specifies whether to enable the PIM-DM State Refresh option
Syntax
ip pim state-refresh-capable
no ip pim state-refresh-capable
Mode
Interface Configuration
Parameters
none
Description
The ip pim state-refresh-capable command specifies whether to enable the PIM-DM State Refresh option. Use this command to optimize network traffic by reducing the amount of flooding and pruning that occurs.
Default
The state refresh capability is enabled by default.
Command History
NGC 2.2 - This command was introduced.
Examples
Example 1
The following example disables the state refresh capability on interface eth3.
(config)# interface eth3
(config-if)# ip pim dense-mode
(config-if)# no ip pim state-refresh-capable
(config-if)# exit
(config)#
Example 2
The following example re-enables the state refresh capability on interface eth3. Note that dense mode was already configured on interface eth3 in Example 1.
(config)# interface eth3
(config-if)# ip pim state-refresh-capable
(config-if)# exit
(config)#
ip pim state-refresh-interval
Name
ip pim state-refresh-interval - specifies the number of seconds between sent State Refresh messages
Syntax
ip pim state-refresh-interval time-seconds
no ip pim state-refresh-interval time-seconds?
Mode
Global Configuration
Parameters
time-seconds - the time in seconds, specified as a non-negative integer between 1 and 255, inclusive
Description
The ip pim state-refresh-interval command specifies the frequency for sending State Refresh messages. The negative form of this command, no ip pim state-refresh-interval, removes the configured value and returns this to its default value of 60 seconds. Note: Specifying a value for time-seconds in the no form of this command has no effect on the configuration. Thus, it is displayed above as optional.
Default
If ip pim state-refresh-interval is not specified, it is the same as if the user had specified the following:
(config)# ip pim state-refresh-interval 60
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the state refresh interval to be 70 seconds.
(config)# ip pim state-refresh-interval 70
ip pim state-refresh-rate-limit
Name
ip pim state-refresh-rate-limit - configures the minimum number of seconds that must pass before a source-group combination will accept another State Refresh message
Syntax
ip pim state-refresh-rate-limit time-seconds
no ip pim state-refresh-rate-limit time-seconds?
Mode
Global Configuration
Parameters
time-seconds - an integer between 0 and 254, inclusive, specifying a number of seconds
Description
Use the ip pim state-refresh-rate-limit command to specify the minimum length of time that must pass before another State Refresh message will be accepted for a particular source-group combination. The negative form of this command, no ip pim state-refresh-rate-limit, removes the configured time-seconds value and returns this to its default value of 30 seconds. Note: Specifying a value for time-seconds in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If ip pim state-refresh-rate-limit is not specified, it is the same as if the user had specified the following:
(config)# ip pim state-refresh-rate-limit 30
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the state refresh rate limit value to be 45 seconds.
(config)# ip pim state-refresh-rate-limit 45
ip pim state-refresh-ttl
Name
ip pim state-refresh-ttl - configures the TTL value that will be used in state refresh messages originated by this router
Syntax
ip pim state-refresh-ttl num
no ip pim state-refresh-ttl num?
Mode
Global Configuration
Parameters
num - an integer from 1 to 255, inclusive
Description
Use the ip pim state-refresh-ttl command to configure the Time-To-Live (TTL) value that will be used in state refresh messages originated by this router. The negative form of this command, no ip pim state-refresh-ttl, removes the configured num value and returns this to its default value of 255. Note: Specifying a value for num in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If ip pim state-refresh-ttl is not specified, it is the same as if the user had specified the following:
(config)# ip pim state-refresh-ttl 255
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures the state refresh TTL to be 100.
(config)# ip pim state-refresh-ttl 100
ip pim dense trace file
Name
ip pim dense trace file - specifies the file to receive tracing information, the size of the file, whether to overwrite existing files, and the maximum number of files allowed
Syntax
ip pim dense trace file file_name [no-timestamp || overwrite]?
no ip pim dense trace file file_name [no-timestamp || overwrite]?
Mode
Global Configuration
Parameters
file_name - specifies the name of the file to receive the tracing information. Note that the file name is not specified in quotes.
no-timestamp - specifies that a timestamp should not be prepended to all trace lines
overwrite - specifies to begin tracing by appending or truncating an existing file
Description
The trace file command is associated with each protocol, so that information pertaining to a single protocol can be written to its own file. The ip pim dense trace file command specifies a file for tracing of all PIM-DM events. The negative form of this command disables this tracing. The specific events that are traced are controlled by the ip pim dense trace flag command.
The no-timestamp option disables the pre-pending of a timestamp to all lines written to the trace file. The default is to prepend a timestamp to all lines written to a trace file.
The overwrite option specifies whether to start tracing by truncating or appending to an existing file.
Note: These options are not cumulative across multiple commands. Consider the following example:
(config)# ip pim dense trace file /var/log/pimdm.log no-timestamp
(config)# ip pim dense trace file /var/log/pimdm.log
The option given in the second command completely replaces that given in the first.
Default
PIM-DM tracing is turned off by default.
Command History
NGC 2.2 - This command was introduced.
Examples
In the following example, PIM-DM tracing is written to the file "/var/tmp/pimdm.log". No timestamp will display at the beginning of the trace lines.
(config)# ip pim dense trace file /var/tmp/pimdm.log no-timestamp
ip pim dense trace flag
Name
ip pim dense trace flag - specifies PIM-DM-specific tracing options as well as options that are common across all protocols
Syntax
ip pim dense trace flag ( [ route | normal | state |
policy | task | timer | all | alert | debug ] ) |
( [ assert | graft | hello | packets | state-refresh ]
[ send | receive | send-receive ]? [detail?] )
no ip pim dense trace flag ( [ route | normal | state |
policy | task | timer | all | alert | debug ] ) |
( [ assert | graft | hello | packets | state-refresh ]
[ send | receive | send-receive ]? [detail?] )
Mode
Global Configuration
Parameters
Flags common to all protocols:
[ route | normal | state | policy | task | timer | all ] - These tracing flags are common to all protocols. They cannot be associated with a send, receive, or send-receive action item. Similarly, you cannot specify to show detailed information when tracing these flags. These flags are defined as follows:
route - trace routing table changes for routes installed by this protocol or peernormal - trace normal protocol occurrences. Note: Abnormal protocol occurrences are always traced.state - trace state machine transition in the protocolpolicy - trace the application of protocol and user-specified policy to routes being imported or exportedtask - trace system interface and processing associated with this protocoltimer - trace timer usage by this protocolall - turns on all trace flags
IM-specific flags that do not allow associated action items:
[ alert | debug ] - These PIM-DM-specific flags cannot be associated with the send, receive, send-receive, or detail action items. These flags are defined as follows:
alert - trace certain failures, such as memory allocation failures, that result in a strong warningdebug - extra trace information of use mainly to developers
IM-specific flags that allow associated action items:
[ assert | graft | hello | packets | state-refresh ] - These PIM-DM-specific flags can be associated with the send, receive, send-receive, and detail action items. These flags are defined as follows:
assert - specifies to trace PIM-DM Assert packetsgraft - specifies to trace PIM-DM graft messageshello - specifies to trace PIM-DM Hello packetspackets - specifies to trace PIM-DM packetsstate-refresh - specifies to trace PIM-DM state-refresh messages
[ send | receive | send-receive ]? - optionally specify whether to limit the tracing to packets sent, received, or both
[detail?] - optionally specify to use a more verbose format when displaying information about the contents of packets instead of one or two lines
Description
Use the ip pim dense trace flag command to specify tracing flags for PIM-DM tracing. Each flag must reside on its own configuration line. For example, you cannot specify to trace both assert and graft packets in the same command.
Default
The default is for no flags to be explicitly configured.
Command History
NGC 2.2 - This command was introduced.
Examples
In the following example, trace flags specify that both the sent and received state-refresh and graft messages are traced in detail. This tracing information will be written to the file /var/tmp/pimdm.log.
(config)# ip pim dense trace file /var/tmp/pimdm.log
(config)# ip pim dense trace flag state-refresh send-receive detail
(config)# ip pim dense trace flag graft send-receive detail
show ip pim dense-mode interface-summary
Name
show ip pim dense-mode interface-summary - displays summarized information about interfaces currently running PIM Dense Mode
Syntax
show ip pim dense-mode interface-summary
Mode
User Execution
Parameters
none
Description
The show ip pim dense-mode interface-summary query displays a summary of the number of interfaces currently running PIM-DM.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example displays information returned in response to the Dense Mode Interface Summary query.
> show ip pim dense-mode interface-summary
PIM Dense Mode Interface Summary
Number of active interfaces 100
Field Descriptions
The following table describes the fields that appear in the PIM-DM MRT Summary Query.
PIM-DM MRT Summary Query Fields
Field
|
Description
|
Number of active interfaces
|
The number of active interfaces in PIM Dense Mode
|
show ip pim dense-mode mrt
Name
show ip pim dense-mode mrt - displays detailed information about S,G entries
Syntax
show ip pim dense-mode mrt [ group group-prefix ||
source source-prefix ]?
Mode
User Execution
Parameters
group group-prefix - optionally specify a group prefix in the format a.b.c.d/e
source source-prefix - optionally specify a source prefix in the format a.b.c.d/e
Description
The show ip pim dense-mode mrt query displays detailed information about S,G entries in the Multicast Routing Table.
Command History
NGC 2.2 - This command was introduced.
Examples
Example 1
The following example displays detailed MRT information for all S,G entries present.
> show ip pim dense-mode mrt
224.1.1.1
192.168.10.1 uptime 01:02:09
Incoming interface: fxp1, index 2, vif 1
Outgoing interface list:
fxp2, index 3, vif 2
fxp3,index 4, vif 3
192.168.121.1 uptime 12:12:12
Incoming interface: fxp2, index 3, vif 2
Outgoing interface list:
fxp1, index 2, vif 1
226.2.2.2
* uptime 02:03:24
Incoming interface: null
Outgoing interface list:
fxp2, index 3, vif 2
10.1.1.1 uptime 00:10:13
Incoming interface: fxp3, index 4, vif 3
Outgoing interface list:
fxp2, index 3, vif 2
Example 2
The following query displays detailed MRT information for group prefix 226.0.0.0/24.
> show ip pim dense-mode mrt group 226.0.0.0/24
226.2.2.2
* uptime 02:03:24
Incoming interface: null
Outgoing interface list:
fxp2, index 3, vif 2
10.1.1.1 uptime 00:10:13
Incoming interface: fxp3, index 4, vif 3
Outing interface list:
fxp2, index 3, vif 2
Example 3
The following query displays detailed MRT information for group prefix 226.0.0.0/24 with source prefix 10.0.0.0/8.
> show ip pim dense-mode mrt group 226.0.0.0/24
source 10.0.0.0/8
226.2.2.2
10.1.1.1 uptime 00:10:13
Incoming interface: fxp3, index 4, vif 3
Outgoing interface list:
fxp2, index 3, vif 2
Field Descriptions
The following table describes the fields that appear in the PIM-DM MRT Detail Information Query (using fields in Example 3).
PIM-DM MRT Detail Information Query Fields
Field
|
Description
|
226.2.2.2
|
Address of multicast group
|
10.1.1.1
|
IP address of source
|
uptime
|
Amount of time the entry has existed
|
fxp3
|
The physical interface name
|
index
|
The interface index
|
vif
|
The interface vif number
|
show ip pim dense-mode mrt-summary
Name
show ip pim dense-mode mrt-summary - displays summarized information about the PIM-DM Multicast Routing Table
Syntax
show ip pim dense-mode mrt-summary
Mode
User Execution
Parameters
none
Description
The show ip pim dense-mode mrt-summary query displays a summary of the number of S,G entries present in the Multicast Routing Table.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example displays information returned in response to the Dense Mode MRT Summary query.
> show ip pim dense-mode mrt-summary
PIM DM MRT Summary
Number of S,G entries 100
Field Descriptions
The following table describes the fields that appear in the PIM-DM MRT Summary Query.
PIM-DM MRT Summary Query Fields
Field
|
Description
|
Number of S,G entries
|
The number of entries in the MRT
|
show ip pim grafts
Name
show ip pim grafts - displays information about unacknowledged grafts
Syntax
show ip pim grafts
Mode
User Execution
Parameters
none
Description
The show ip pim grafts query displays information about unacknowledged grafts.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example information displays as a result of the show ip pim grafts query.
> show ip pim grafts
PIM Graft Information
192.168.10.1, 224.1.1.1 age 00:00:24 retransmit in
00:00:02
Field Descriptions
The following table describes the fields that appear in the PIM-DM Graft Retransmission Query.
PIM-DM Graft Retransmission Query Fields
Field
|
Description
|
192.168.10.1
|
Address of the source
|
224.1.1.1
|
Address of the group
|
age
|
Amount of time that graft has been unacknowledged
|
retransmit in
|
Time left until the next transmission of graft
|
|
