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Beginner

Cat 9300 Output Drops

Hi,

 

I have 2 x c9300-48U switches running 16.6.4a, data and power stacked in a corporate office. I have a 100MB carrier link on Gi1/0/48 back to our DC. I'm running OSPF for routing across this interface to our DC. There are no known performance issues at the office. The link is doing almost nothing at the moment (57k bit/s), but I can see output drops on the interface. When I deployed the switches I had an outbound QoS shaping policy on the interface and I thought that this may be been contributing to the drops, but I've since removed the policy and can still see the output drops. The drops happen in bursts, not constantly. I wouldn't expect that this is due to micro bursts, it's a corporate office, not a DC. These are the only Cat 9300s that we have deployed so I have no reference point. Has anyone seen this issue before?

 

Switch#show run inter gi1/0/48
interface GigabitEthernet1/0/48
switchport access vlan 600
switchport mode access
bandwidth 100000
ip flow monitor Netflow-Monitor input
ip flow monitor Netflow-Monitor output
spanning-tree portfast disable
spanning-tree link-type point-to-point
!
Switch#show inter gi1/0/48
GigabitEthernet1/0/48 is up, line protocol is up (connected)
Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:03, output hang never
Last clearing of "show interface" counters 00:07:35
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 90454
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 41000 bits/sec, 18 packets/sec
5 minute output rate 58000 bits/sec, 18 packets/sec
8345 packets input, 2662939 bytes, 0 no buffer
Received 357 broadcasts (357 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 357 multicast, 0 pause input
0 input packets with dribble condition detected
9601 packets output, 3469147 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

 

Switch#show inter gi1/0/48
GigabitEthernet1/0/48 is up, line protocol is up (connected)
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:00:01, output hang never
Last clearing of "show interface" counters 00:36:32
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 619164
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 43000 bits/sec, 15 packets/sec
5 minute output rate 58000 bits/sec, 18 packets/sec
44165 packets input, 16395160 bytes, 0 no buffer
Received 1694 broadcasts (1693 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 1693 multicast, 0 pause input
0 input packets with dribble condition detected
49762 packets output, 17725791 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

 

Switch#show inter gi1/0/48 summary

*: interface is up
IHQ: pkts in input hold queue IQD: pkts dropped from input queue
OHQ: pkts in output hold queue OQD: pkts dropped from output queue
RXBS: rx rate (bits/sec) RXPS: rx rate (pkts/sec)
TXBS: tx rate (bits/sec) TXPS: tx rate (pkts/sec)
TRTL: throttle count

Interface IHQ IQD OHQ OQD RXBS RXPS TXBS TXPS TRTL
-----------------------------------------------------------------------------------------------------------------
* GigabitEthernet1/0/48 0 0 0 705796 37000 18 58000 20 0

Switch#show inter gi1/0/48 counters err

Port Align-Err FCS-Err Xmit-Err Rcv-Err UnderSize OutDiscards
Gi1/0/48 0 0 0 0 0 705796

Port Single-Col Multi-Col Late-Col Excess-Col Carri-Sen Runts
Gi1/0/48 0 0 0 0 0 0

 

Switch#sh platform hardware fed switch 1 qos queue stats interface gigabitEthernet 1/0/48

DATA Port:47 Enqueue Counters
-------------------------------
Queue Buffers Enqueue-TH0 Enqueue-TH1 Enqueue-TH2
----- ------- ----------- ----------- -----------
0 0 0 62774524860 29167976599
1 0 0 0 56648358534
2 0 0 0 0
3 0 0 0 0
4 0 0 0 0
5 0 0 0 0
6 0 0 0 0
7 0 0 0 0

DATA Port:47 Drop Counters
-------------------------------
Queue Drop-TH0 Drop-TH1 Drop-TH2 SBufDrop QebDrop
----- ----------- ----------- ----------- ----------- -----------
0 0 712750 1993711628 0 0
1 0 0 206309804 0 0
2 0 0 0 0 0
3 0 0 0 0 0
4 0 0 0 0 0
5 0 0 0 0 0
6 0 0 0 0 0
7 0 0 0 0 0

Note: Queuing stats are in bytes

 

Cheers,
Tom

3 REPLIES 3
VIP Expert

Re: Cat 9300 Output Drops

Hi Tom,

Have you talked to the provider to make sure the circuit is good end-to-end? Also, have you tried a different patch cable, maybe a different port and also removing the bandwidth command and test?

HTH

VIP Expert

Re: Cat 9300 Output Drops

Is there more than one LAN client at 100 Mbps, or any LAN clients with gig? If so, either can generate transient congestion on your 100 Mbps egress port. Adjusting drop thresholds might mitigate.
Beginner

Re: Cat 9300 Output Drops

Just to sign this off (a while back now), I realised from some old outputs that the interface had negotiated at 1Gb when I first bought it up, however after a reboot it had negotiated at 100Mb. I had a local contact unplug/plug the cable and it correctly negotiated at 1Gb. The interface errors went away.
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