Multicast Rate-Limit

During the preparations for multicast I stumbled across the ip multicast rate-limit command. The command itself is nothing special but the logic on how to define which source and multicast groups to rate-limit is somehow, at last if you got the same logic as myself.
So to start with, for me if I have to define something based on a source (multicast source in this case) and a destination (multicast group(s)) I first specify the source and afterwards the destination. Sounds logic or not? I dont know but I hope I do not belong to a small group of persons with a strange logic, cause the people that wrote the code for the command have a different one ;)

It looks like that at last for the multicast rate-limit the logic is different. But lets start with the basic usage of the command.

The command is configured at interface level and got the following syntax:

router(config-if)# ip multicast rate-limit {in ¦ out} {video ¦ whiteboard} {group-list access-list} {source-list access-list} kbps

in Rate-limits on ingress pakets
out Rate-limits on egress pakets
video (Optional) Rate-limits based on the defined UDP port numbers for video traffic. The Session Announcement Protocol (SAP) chache identifies the video traffic.
whiteboard (Optional) Rate-limits based on the defined UDP port numbers for whiteboard traffic. The Session Announcement Protocol (SAP) chache identifies the whiteboard traffic.
group-list access-list (Optional) Defines the standard ACL to match the multicast group(s)
source-list access-list (Optional) Defines the standard ACL to match the multicast source(s)
kbps Defines the maximum transmission rate. All packets above this rate get dropped without further notice. The default is set to 0 (no traffic at all)

The SAP cache gets activated with the command ip sap listen. There will be no rate-limiting for video or whiteboard traffic if the SAP cache did not get activated.

So a rate-limiting based on the group and source is configured like this:

interface FastEthernet0/0
 ip address 116.1.1.1 255.255.255.0
 ip pim sparse-dense-mode
 ip multicast rate-limit out group-list GROUP source-list SOURCE 64
 duplex auto
 speed auto
!
ip access-list standard GROUP
 permit 239.1.1.1
ip access-list standard SOURCE
 permit 116.2.3.2

But, and thats what really got me while trying to configure it without the configuration guide only using the ?, you can not configure this if you try to specify the source first:

Router(config-if)# ip multicast rate-limit out source-list SOURCE ?
  <0-4294967>  Rate in kilobits per second
  video        Rate limit video only
  whiteboard   Rate limit whiteboard only
  <cr>

Router(config-if)#ip multicast rate-limit out group-list GROUP ?
  <0-4294967>  Rate in kilobits per second
  source-list  Rate limit for sources
  video        Rate limit video only
  whiteboard   Rate limit whiteboard only
  <cr>

Its not too bad if it doesnt work but I had to read it first cause I somehow did only try to configure the source and then the group. Now I know it :D

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