Multicast causing high CPU

[derawat28]

Hi,

In my network we are facing high CPU causing because of multicast traffic...

The source of mylticast having 155.x.x.x and Group 239.x.x.x.

currently we have placed a access-list to stop causing high CPU as below but now concerned is that we are not able to get the multicast video from this source.

access-list 1 deny 239.0.0.0 0.255.255.255

When we take out the above acl so again it causing the high CPU.. I have checked the and found the RPF failure as below,

ds1#sh ip mroute 239.x.x.x count

IP Multicast Statistics

102 routes using 77310 bytes of memory

29 groups, 2.51 average sources per group

Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second

Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 239.x.x.x, Source count: 1, Packets forwarded: 0, Packets received: 467885775

RP-tree: Forwarding: 0/0/0/0, Other: 0/0/0

Source: 155.x.x.x/32, Forwarding: 0/-92/0/0, Other: 467885775/20990877/446894898

Please anyone can help to find the issue and how we may resolve it?

Appreciate your time and efforts for me.

Thanks and Regards

[FON Wireless LTD]

239.0.0.0/8 is a reserved range for ssm multicast, and treated a bit differently that other ranges inside 224.0.0.0/4 and; if it is not configured with:

ip pim ssm default
no ip igmp ssm-map query dns
ip igmp ssm-map enable

The traffic to that range is punted and sent to the cpu.

H.

[Harold Ritter]

Hi @FON Wireless LTD ,

The reserved range for SSM is 232/8 as per RFC3569, section 6.1. 

https://datatracker.ietf.org/doc/html/rfc3569

Regards,