All things related to multicast

[Stig Venaas <>]

Paul Chang wrote:
> Folks,
>
> Anyone has similar problem on this?
>
> When Powerquest drivemage set TTL=1, the nearest L3 switch (6513 in this 
> case) has CPU utilization goes beyond 98%. If I adjusted the TTL=x to 
> match how many hop the RP is, both the nearest L3 switch and RP has high 
> CPU utilzation goes beyond 90%. The switch did not die in this case, but 
> all software relate process were crawling.

There was a mail regarding this sent to the list by Brian Field in 
February. He wrote:

> Re hardware rate limiting of TTL=1 on the sup 720, check out
> "mls rate-limit all ttl-failure pps burst". Note that this
> applies to both multicast and unicast traffic.
>
> There are a number of other handy multicast specific hardware
> rate limiters under "mls rate-limit multicast".

This is for 6509 with sup720, but is probably valid for some other 
systems (at least recent ones, not older supervisors).

You may also see
http://www.cisco.com/en/US/partner/products/hw/switches/ps708/products_tech_note09186a00804916e0.shtml

Stig

> My work-around is to turn off the "ip PIM sparse-mode" at the vlan where 
> Mcast source and destinations are taken place (all within on vlan). This 
> works fine since L2 Cisco 35xx has IGMP-snooping turned on. Usually, 1 
> /40 source/destination ratio for computer lab imaging building is 
> conducted.
>
> I have Cisco TAC given me the followings
>
> http://www.cisco.com/en/US/products/hw/switches/ps708/products_white_paper0900aecd802ca5d6.shtml 
>
>
> Some data-plane traffic may have to be processed in software as well. 
> This type of traffic is referred to as data-plane "punt" traffic. 
> Examples of software-processed data-plane packets include:
>
> • Packets with IP options
>
> • Packets with time-to-live (TTL) field equal to 1
>
>
> which looks to me a design flaw of the control plane.
>
> Anyone has a better way to deal with this? Please advice,
>
> P a u l C h a n g Network Engineer
> University of New Mexico
> Computer & Information Resources & Technology
> 2701 Campus Boulevard NE, Albuquerque, NM 87131
> Phone: (505) 277-8257 FAX: (505) 277-8101