Basic Multicasting

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We are trying to set up basic multicasting (Single VLAN no multicast across subnets) for the purpose of workstation imaging (Apple Software Restore, Ghost, Zenworks, etc.). We are able to multicast, but increasing the multicast rate to an acceptable level floods the network. It appears that the multicast packets are being replicated out to all switch ports on the vlan.


Network architecture: Main switch - Catalyst 4506 w/IGMP snooping globally enabled.

Multicast server switch - Catalyst 3550-12T w/IGMP snooping globally enabled and connected to main switch via 1000Mb link.

Workstation switches - a combination of 3550 and 2924 switches connected directly to main switch via 100Mb or 1000Mb links. IGMP settings at factory defaults.

Site router - 7206VXD. No configuration made for multicasting. (I don't want any of the multicast traffic to cross the router - I want it all to stay local)


What am I missing? How do I ensure that the multicast packets are only replicated to the ports that are part of the group?


Thank you for any help.

Mark Leach

Correct Answer by Jon Marshall about 10 years 2 weeks ago

Mark


Glad you got it working. I haven't used Cisco MRM so i can't really comment on why you were seeing packet loss.


If i get a chance next week i'll have a look at MRM in our lab.


Jon

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Jon Marshall Thu, 07/05/2007 - 11:44
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Hi Mark


You have IGMP snooping turned on but do you have anything acting as an IGMP querier.

If you haven't think of it like this. IGMP listens to responses but something has to ask the question.


You need to look into the switch acting as an IGMP querier. Some Catalyst switches have this functionality.


Attached is a link to a cisco doc for troubleshooting multicast on a single vlan. If your switch doesn't support IGMP querier function then there are some possible alternatives in this doc.


http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008059a9df.shtml


HTH


Jon

Thank you for your response and pointing me to that doc. I seem to have things working now, but am still confused about something.


I have attached a text document with detailed network layout, configs, and SHOW command results.


I enabled PIM sparse mode on VLAN1 of the 4506. I then set up a test environment using Cisco's MRM to try things out. The output seemed to indicate 100% packet loss and that multicast was still not set up properly (see stats in attachment).


After playing with different settings this morning and not getting the MRM test environment to do anything but show 100% packet loss I decided to try a live multicast for the heck of it. The multicast session worked very well (24 workstations attached to CHS_CISCO_MACLAB_01 and a source server on GigabitEthernet 0/3 of CHS_CISCO_SERVER_01) without forwarding packets to anything but the necessary ports on the 4506.


So, some change I made seems to have worked. But, why is the MRM output showing a problem? Am I still missing something?



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Jon Marshall Fri, 07/06/2007 - 11:42
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Mark


Glad you got it working. I haven't used Cisco MRM so i can't really comment on why you were seeing packet loss.


If i get a chance next week i'll have a look at MRM in our lab.


Jon

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