Hello to everyone!
Some time ago we replaced our stack of 3850 with two 9300. It had been working fine for a while but recently we noticed huge broadcast drops (especially DHCP) with low-to-moderate utilization. Both client and DHCP server are directly connected to same switch. When capturing traffic I see that about 90% of DHCP Discovery packets in some specific time frame are being drop by switch. Interface load is very low (up to 10Mbps).
Here is output
Stack9300-8#show controllers cpu-interface
queue retrieved dropped invalid hol-block
-------------------------------------------------------------------------
Routing Protocol 104556267 0 0 0
L2 Protocol 793799606 0 0 0
sw forwarding 104618376 33082001 0 0
broadcast 144435817 33652699 0 0
icmp gen 0 0 0 0
icmp redirect 671994797 0 0 0
logging 50895 0 0 0
rpf-fail 0 0 0 0
DOT1X authentication 0 0 0 0
Forus Traffic 78237539 0 0 0
Forus Resolution 266176270 0 0 0
Inter FED 0 0 0 0
L2 LVX control 0 0 0 0
EWLC control 0 0 0 0
EWLC data 0 0 0 0
L2 LVX data 0 0 0 0
Openflow 0 0 0 0
Topology control 16718231 0 0 0
Proto snooping 0 0 0 0
DHCP snooping 0 0 0 0
Transit Traffic 0 0 0 0
Multi End station 27641757 0 0 0
Webauth 0 0 0 0
High rate app 0 0 0 0
Exception 0 0 0 0
System Critical 0 0 0 0
NFL sampled data 0 0 0 0
Low latency 0 0 0 0
EGR exception 15079 0 0 0
Stackwise Virtual OOB 0 0 0 0
Multicast data 0 0 0 0
Gold packet 0 0 0 0
Stack9300-8#sh clo
Stack9300-8#sh clock
14:25:40.066 EET Fri Mar 12 2021
Stack9300-8#
Stack9300-8#
Stack9300-8#
Stack9300-8#
Stack9300-8#sh clock
14:33:35.268 EET Fri Mar 12 2021
Stack9300-8#sh clock ow controllers cpu-interface
queue retrieved dropped invalid hol-block
-------------------------------------------------------------------------
Routing Protocol 104557874 0 0 0
L2 Protocol 793811484 0 0 0
sw forwarding 104620296 33082666 0 0
broadcast 144437541 33653005 0 0
icmp gen 0 0 0 0
icmp redirect 672252888 0 0 0
logging 50895 0 0 0
rpf-fail 0 0 0 0
DOT1X authentication 0 0 0 0
Forus Traffic 78238993 0 0 0
Forus Resolution 266181377 0 0 0
Inter FED 0 0 0 0
L2 LVX control 0 0 0 0
EWLC control 0 0 0 0
EWLC data 0 0 0 0
L2 LVX data 0 0 0 0
Openflow 0 0 0 0
Topology control 16718479 0 0 0
Proto snooping 0 0 0 0
DHCP snooping 0 0 0 0
Transit Traffic 0 0 0 0
Multi End station 27643233 0 0 0
Webauth 0 0 0 0
High rate app 0 0 0 0
Exception 0 0 0 0
System Critical 0 0 0 0
NFL sampled data 0 0 0 0
Low latency 0 0 0 0
EGR exception 15079 0 0 0
Stackwise Virtual OOB 0 0 0 0
Multicast data 0 0 0 0
Gold packet 0 0 0 0
Stack9300-8#
_____________________________
Switch Ports Model SW Version SW Image Mode
------ ----- ----- ---------- ---------- ----
* 1 64 C9300-48UXM 16.9.2 CAT9K_IOSXE INSTALL
2 64 C9300-48UXM 16.9.2 CAT9K_IOSXE INSTALL
Any clue what can go wrong?
