11-30-2018 08:20 AM
I believe that this bug, or a variation of it, is present in 16.3.7 as well. We have been fighting a high CPU issue with SISF switcher since upgrading to 16.3.7 as well and initially applied this to just the trunk links as described. After a number of attempts to resolve this issue failed and even splitting the stack into 2 smaller stacks failed we put the IPv6 filer into the user interfaces and this stopped the issue immediately. We could not identify any clear signs that there was a "flood" of traffic going on.
Prior to applying the filter to the switch ports:
switch#sh proc cpu sorted CPU utilization for five seconds: 95%/38%; one minute: 94%; five minutes: 94% PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process 299 16210718 412251 39322 48.85% 45.78% 45.60% 0 SISF Switcher Th 225 949559 115216 8241 2.06% 1.73% 1.73% 0 Spanning Tree
This was applied to each bank of ports:
switch(config-if-range)#ipv6 traffic-filter DENY-IPV6 in switch(config-if-range)#int range g2/0/1-48
CPU usage afterwards:
switch#sh proc cpu sorted CPU utilization for five seconds: 18%/5%; one minute: 34%; five minutes: 73% PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process 225 959669 116139 8263 1.91% 1.76% 1.76% 0 Spanning Tree 74 1581721 536829 2946 1.75% 3.13% 3.14% 0 IOSD ipc task