Hello!
This is just for information for anybody who has the problem on Cat3850 platform.
We had the same issue on WS-C3850-24XS-E, Version 16.6.4
The CPU was quiet high (peaks) -> after removing "ip dhcp snooping vlan 1-4094" the CPU decreased significant.
Those two processes generated that high CPU:
478 1071381667 153333886 6987 37.51% 19.57% 19.45% 0 SISF Switcher Th
479 763884804 142905654 5345 24.55% 14.02% 13.90% 0 SISF Main Thread
SISF = Switch Integrated Security Features
Removing the feature "ip dhcp snooping trust" on the interfaces had no improvement.
removing the global config "ip dhcp snooping vlan 1-4094" solved the high CPU
btw: "ip dhcp snooping" was not applied -> DHCP snooping was disabled.
BEFORE:
755555222228888844444333337777766666777779999999999444445555
711111555551111199999111115555588888222222222255555888885555
100 *****
90 **********
80 * ***** ***** **********
70 * ***** *************************
60 * ***** ************************* **
50 ****** ********** ********************************
40 ****** ********** ********************************
30 **********************************************************
20 **********************************************************
10 **********************************************************
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per second (last 60 seconds)
AFTER: (no ip dhcp snooping vlan 1-4094)
1111111111111111111122222555555555577777222225555577777222
991111100000111115555522222333338888855555666669999922222666
100
90
80 *****
70 ***** *****
60 ********** **********
50 *************** **********
40 *************** **********
30 *******************************
20 *****************************************
10 **********************************************************
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per second (last 60 seconds)
1111111111 111111111111111 111111111111111
888889999900000000009999900000000001111199999111110000011111
100
90
80
70
60
50
40
30
20
10 **********************************************************
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per second (last 60 seconds)
We need to do further investigation on why this is happening. We just can say, that this has to do with IPv6-Packets (wireshark capture)
I will update this discussion as soon as we have results.
Thomas
