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

[Martin T]

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
>
>