enabling some multicast group across a WAN link

Answered Question
Feb 21st, 2008
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Hi,


I am fairly new to multicast but I was asked to enable multicast across our WAN but only to a certain group of addresses. How do I accomplish this?

Correct Answer by Edison Ortiz about 9 years 2 months ago


> can I just use ip multicast boundary on remoteswitch?


Yes, please see this link on more information regarding that command:

http://www.cisco.com/en/US/docs/ios/12_3/ipmulti/command/reference/ip3_i1g.html#wp1075549


HTH,


__


Edison.




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Edison Ortiz Thu, 02/21/2008 - 08:16
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I highly recommend reading Configuring Basic IP Multicast document at:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/himc_c/chap05/mcbbasic.htm

in order to understand what options are available to you.


1) You need to enable multicast in the WAN interfaces and interfaces where the multicast host and servers will reside.


2) You need to choose how you are going to distribute the multicast information (static RP, Auto-RP, BSR, etc).


3) Based on the chosen method, you apply the necessary 'group-list' for the requested multicast groups.


HTH,


__


Edison.

Tshi M Thu, 02/21/2008 - 08:47
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Thanks for the link and will go through it. MCAST is already enabled on one side of the link. Basically I'd like to know if the order side can be configured just query some groups. My understanding is that only requested groups will send across the link. Is that right?

The core switches have the following config (see attached).

We want the other side just be able to access:

239.255.46.11

239.255.46.12

239.255.46.13

239.255.46.14

239.255.46.15

And Multicast/unicast for 239.255.46.1



my intent was to only add ip pim sparse-dense-mode on the the serial interfaces and the VLAN where the servers belong






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Edison Ortiz Thu, 02/21/2008 - 08:54
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I don't recommend enabling dense on WAN links as it has a flooding behavior. Just enable ip pim sparse mode and configure a RP.


The RP will have the group-list that will contain the multicast groups that it should announce to other multicast routers.


Read the link I posted and everything will make sense. If you have additional questions, feel free to post back.


HTH,


__


Edison.

Tshi M Thu, 02/21/2008 - 12:27
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Ok, below is what I am planning to configure


core switches running auto-RP (RP address 10.33.63.1)<-->Remote switche <--->switchSite1


I was going to configure switchsite1 as below

ip multicast-routing

interface G0/1 (connecting to Remote switch at headquarter)

ip pim sparse-mode


ip pim rp-address 10.33.63.1 access-list 99 override


access-list 99 permit 239.255.46.1

access-list 99 permit 239.255.46.11

access-list 99 permit 239.255.46.12

access-list 99 permit 239.255.46.13

access-list 99 permit 239.255.46.14

access-list 99 permit 239.255.46.15


remote switch

int g0/2

ip pim sparse-mode


would this work?

Edison Ortiz Thu, 02/21/2008 - 12:44
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Since you've decided to configure Static RP, not Auto-RP, you need to also enter the Static RP information in the remote switch.


ip pim rp-address 10.33.63.1


Tshi M Thu, 02/21/2008 - 13:18
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The remote switch already knows about the rp address. see below:


remoteswitch#sh ip pim rp mapping

PIM Group-to-RP Mappings


Group(s) 224.0.0.0/4

RP 10.33.63.1 (?), v2v1

Info source: 10.10.10.10 (?), elected via Auto-RP

Uptime: 1w1d, expires: 00:02:25


remoteswitch#sh ip pim rp

Group: 239.255.45.41, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.255.250, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.43, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.32, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.34, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.24, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.22, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.46.14, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.46.15, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.46.12, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.46.13, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.46.11, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.4, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.46.5, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.1, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.2, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.46.1, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.103, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.102, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.140.2, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.141.2, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Group: 239.255.45.132, RP: 10.33.63.1, v2, uptime 1w1d, expires 00:02:33

Edison Ortiz Thu, 02/21/2008 - 13:37
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So you are using Auto-RP but you aren't filtering the Auto-RP group-list.


Per your output


Group(s) 224.0.0.0/4


covers all multicast groups.


The portion of the config you posted reflects a static RP configuration. You must have additional multicast information in your router for Auto-RP which you haven't posted.


Tshi M Thu, 02/21/2008 - 13:43
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We have two core switches configuring for Auto-RP. The switch called RemoteSwitch connect to those core switches internally. The RemoteSwitch is then connected to another switch that I called switchSite1 via a 20Mb Ethernet circuit. SwitchSite1 is the one requesting mcast information via RemoteSwitch.


CoreSwitch<->RemoteSwitch<20Mb>SwitchSite1.

Tshi M Thu, 02/21/2008 - 14:38
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Since I want to restrict the groups going from remoteswitch to switchsite1, can I just use ip multicast boundary on remoteswitch? This is an effect will deny any other groups from going across the 20Mbps circuit. Please advise.

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