[c-nsp] unicast IPv4 packets punted on Cisco 4500

[Andras Toth]

Hi Martin,

On Catalyst 4500 the MAC learning is done by CPU.

Catalyst 6500 (at least with Sup32 & Sup720), and Nexus switches perform
MAC learning in hardware.

Best regards,
Andras


On Wed, Oct 22, 2014 at 1:58 PM, Martin T <m4rtntns at gmail.com> wrote:

> Hi,
>
> thanks for all the replies! I overlooked the "SA Miss" field. I guess
> the reason why source MAC address needs to be re-learned is that it's
> flapping between the ports Gi6/45 and Gi6/48. As I explained,
> "Ethernet tester" sends out frames with source MAC address
> 00:00:00:00:00:11 and destination MAC address 00:18:63:00:32:76 to
> Gi6/45 port and those frames are hardware-looped to port Gi6/48 with
> the same source MAC address.
> So in order to avoid the high CPU utilization because of source MAC
> address re-learning, I can:
>
> 1) create a static MAC address-table entry("mac address-table static
> 0000.0000.0011 vlan 900 interface GigabitEthernet6/48" or "mac
> address-table static 0000.0000.0011 vlan 900 interface
> GigabitEthernet6/45")
> 2) disable MAC address learning for VLAN 900("no mac address-table
> learning vlan 900")
>
> First command normalizes the CPU usage, but switch seems to drop the
> traffic if MAC address table entry points to a different port where
> the frame came in from. With disabling the MAC address learning I'm
> able to achieve what I needed.
>
>
> Is this Cisco Catalyst 4500 series platform-specific behavior that MAC
> address table entries are done by switch CPU? Or is this so for all
> the Catalyst and Nexus switches?
>
>
> thanks,
> Martin
>
> On 10/21/14, Lukas Tribus <luky-37 at hotmail.com> wrote:
> >> "Event: SA Miss" means that the MAC Source Address needs to be learnt
> (or
> >> re-learnt) so the switch send a copy of the packet to CPU for learning
> the
> >> MAC address. Perhaps the MAC is not learn yet, or the aging timer is too
> >> low, or the MAC is learnt on another port already and it's flapping.
> >
> > Or the traffic generator uses random source mac addresses.
> >
> >
> > Lukas
> >
> >
>