[c-nsp] Filtering Layer 2 Multicasts on 6509
Tóth András
diosbejgli at gmail.com
Thu Jan 20 03:45:06 EST 2011
Hi,
Most multicast traffic is forwarded in hardware on the 6500 platform.
However, in this case, the layer-2 mcast address is not a standard
ieee mcast address which means the packets will be treated like
broadcast.
Standard layer-2 mcast starts like this:
01.00.5e.XX.XX.XX
All broadcast packets are punted to cpu for processing since the cpu
is member of that vlan domain and thus it will review all ARP packets
and other kinds of broadcast packets in that vlan domain.
Resolution options:
There are a couple options here to prevent those packets from being
punted to cpu.
1) I believe you can match those particular mcast packets with a mac
access-list and then drop them before hitting the cpu using control
plane policing. This will require you to enable QoS globally and if
you have not enabled QoS globally already, this is a bad option. Also,
I'm not 100% off top of my head whether you can use mac ACL for
control plane policing.
2) Identify which interfaces require this mcast flow on the 6500. Then
create a static mac entry in your cam table such that the 6500 will
forward this mcast stream out all of those ports which require this
stream:
Switch#conf t
Switch(config)#mac-address-table static <dest_mcast_address> vlan
<vlan_id> interface GigabitEthernet x/y GigabitEthernet x/z
You can assign this mac address to multiple interfaces and even in
multiple vlans.
Best regards,
Andras
On Wed, Jan 19, 2011 at 11:08 PM, Devin Kinch <devinkinch at gmail.com> wrote:
>> If it's true L2 multicast, it shouldn't be hitting your RP from my understanding of L2 Multicast.
>
> I didn't think so either. But when I turn down the SVI interfaces in those VLANs, the CPU usage goes down to around 8-9%. Here's the output showing the CPU usage:
>
> 6686588558665866686568555866585558955866685568667865986558656855686568
> 8371990985129424261948999640989895598405059945041409672886290689060905
> 100 * *
> 90 * * * * * * * ** * * ** * * * *
> 80 * ** * * * * * * ** * * * * ** * * * *
> 70 * * ** * * * * * * ** * * * * ** ** * * * *
> 60 **********************************************************************
> 50 ######################################################################
> 40 ######################################################################
> 30 ######################################################################
> 20 ######################################################################
> 10 ######################################################################
> 0....5....1....1....2....2....3....3....4....4....5....5....6....6....7.
> 0 5 0 5 0 5 0 5 0 5 0 5 0
> CPU% per hour (last 72 hours)
> * = maximum CPU% # = average CPU%
>
> s01#sh proc cpu sort
> CPU utilization for five seconds: 59%/48%; one minute: 61%; five minutes: 61%
> PID TID 5secUtil 1minUtil 5minUtil
> 1 1 41.0% 39.3% 39.3%
> 16406 6 28.8% 28.4% 28.4%
> 16429 4 7.5% 4.8% 2.9%
> 16406 22 7.0% 3.4% 3.3%
> 16406 21 6.5% 3.7% 1.9%
> 16406 17 4.5% 5.9% 3.9%
>
> s01#show proc cpu detail 16406
> CPU utilization for five seconds: 61%/46%; one minute: 61%; five minutes: 61%
> PID/TID 5Sec 1Min 5Min Process Prio STATE CPU
> 16406 51.9% 51.6% 51.4% ios-base 28d18h
> 1 0.0% 0.0% 0.0% 20 Condvar 0.000
> 2 1.7% 1.7% 1.6% 5 Ready 1d01h
> 3 9.2% 3.8% 4.1% 10 Reply 27m38s
> 4 0.0% 0.0% 0.9% 10 Receive 36m35s
> 5 0.0% 0.0% 0.0% 11 Nanosleep 2m21s
> 6 28.3% 28.5% 28.4% 21 Intr 17d05h
> 7 0.9% 1.8% 2.0% 22 Intr 1d05h
> 8 0.9% 0.9% 0.9% 23 Intr 12h23m
> 9 0.0% 0.0% 0.0% 25 Intr 0.000
> 10 0.0% 0.0% 0.1% 10 Receive 24m13s
> 11 0.0% 0.0% 0.0% 10 Receive 58m52s
> 12 0.0% 0.0% 0.0% 10 Condvar 0.001
> 13 0.0% 0.0% 0.0% 10 Receive 53m01s
>
> According to the caps, it's all L2 mcast with an Ethertype of 8819. Which is cobranet. If you want to know more about it, knock yourself out:
> http://www.peaveyoxford.com/kc/Working%20with%20CobraNet.pdf
>
> I tried to filter using VLAN ACL, but it stopped all communication in the VLAN for Ethertype 8819.
>
> On 2011-01-19, at 1:46 PM, Max Pierson wrote:
>
>> Here's more info on VACL's ...
>>
>> http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/vacl.html
>>
>> Apply the VACL to only drop the traffic if its destination to your RP MAC. If it's true L2 multicast, it shouldn't be hitting your RP from my understanding of L2 Multicast. (Someone please correct me if i'm wrong).
>>
>> On Wed, Jan 19, 2011 at 2:40 PM, Devin Kinch <devinkinch at gmail.com> wrote:
>>
>> But then the traffic would also be filtered out as in enters the VLAN... I still need the traffic to pass through the trunk links to the edge aggregation switches at each site. I just need to keep it from hitting the RP.
>>
>> Unless I'm confused about where VACLs apply filtering...
>>
>> On 2011-01-19, at 12:23 PM, Max Pierson wrote:
>>
>>> VACL's should do the trick for you here. If you know the value of the Ethertype frame, you should still be able to filter on it even though it's proprietary. If you don't, time to break out the shark! I would start off by trying to filter based on ethertype since that won't be common to any other traffic on the wire.
>>>
>>> Max
>>>
>>> On Wed, Jan 19, 2011 at 1:54 PM, Devin Kinch <devinkinch at gmail.com> wrote:
>>> I have a network running two 6509's with VSS in the core of the network. Several of the attached VLANs are used by an application that transmits audio with a non-IP based layer 2 multicast (016b.68xx.xxxx or something like that) stream. It uses many different destination MAC addresses and the frames have their own vendor proprietary Ethertype. We also need layer 3 routing in the same VLANs to manage these devices.
>>>
>>> The issue I have is that all these layer 2 multicasts are causing the CPU usage on the Sup to hover at around 70-80%. It isn't causing any noticeable impact to the network today, but it may impact future scalability. I've tried using CoPP (which doesn't support L2 filtering)... is there an obvious, elegant way of filtering this traffic from hitting the RP, while still forwarding at layer 2? Perhaps static MAC entries?
>>>
>>>
>>> Devin Kinch
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>>>
>>
>>
>
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