Recommended Router with Multicast Member recieving 60 groups?

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Feb 12th, 2009
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I encountered a situation where we have a Cisco 870 with a VPN built to another Cisco router. A host behind the Cisco 870 router is a multicast member receiving streams from 60 groups.


Doing that causes high CPU, 99%.


What would be a recommended router that can support a host receiving about 60 multicast groups?


Thank you!

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Edison Ortiz Thu, 02/12/2009 - 12:15
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The limitation is not in the # of groups but the amount of bandwidth each group is sending/receiving.


You need to do some traffic profiling and determine the amount of bandwidth each group is consuming and from there we can recommend not only the hardware but perhaps the WAN speed needed to accommodate the demands.


Perhaps the CPU is high because the high amount of packet drops in the outgoing interface of the router.


HTH,


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Edison.

ryabutler Thu, 02/12/2009 - 13:14
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I agree. The total bandwidth usage for receiving 60 groups was at 4.4Mbps with an ethernet uplink to a cable/dsl device, so it wasn't dropping a lot of packets on the router interface.


However, the cable/dsl is probably like a 1Mbps connection. Could that still cause drops on the router interface side which is an FE connection and is not discarding packets or being congested? The total output drops shows = 0.


My guess is that high traffic rates across the VPN where the 870 is "not strong enough" to encrypt and decrypt fast enough with the rate, so the VPN engine is working a lot harder and using up more CPU cycles. But, show process cpu doesn't show anything unless it's a different command.


Thank you!


Edison Ortiz Thu, 02/12/2009 - 13:27
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Does the 870 has the internal cable/dsl interface, or is it connected FE towards an external device?


4.4Mbps is not bad for a 870. According to the router performance sheet: http://www.cisco.com/web/partners/tools/quickreference/index.html it can deliver up to 12Mbps FE-to-FE BUT if you add the VPN and other service's overhead it can dramatically decrease its performance.


The problem with Multicast is that is bursty by nature so you won't have a sustained 4.4Mbps traffic, it can peak a times.


Addition to that, if you say the WAN connection is only 1Mbps, you have a bottleneck somewhere and packets may be queueing in the router.


As for the show process cpu, care to post the complete output while is running a high %?


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Edison.

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