We've been experiencing for a while now issues with discarded packets on an interface on a 3750, this interface has a server attached that does backups on a nightly basis across our WAN.
When I look at both the interface on the server and the interface on the switch its showing a huge number of discards, these discards seem to follow the pattern of data throughput so as throughput increases so does the discards.
I've read some info about buffers and how these can cause discarded packets when there's none free and I know these can be tweaked but am not confident enough to know exactly what to change and by how much. I've attached the sh buffers from the switch concerned.
I'm in the process of doing a packet capture of the interface to see if the server itself is causing the issue.
If anyone can give me any advice and help it would be much appreciated?
From the outputs, I do not see any issue with software buffers. There are no
buffer drops. I am assuming the issue could be due to hardware buffers where
the interface does not have enough buffer space to hold the incoming data.
Please try the following:
Hold-queue 1024 in
This will increase the hold queue size for that interface. This should help
to some extent. But for a permanent solution, you might want to look at the
rate at which the server is sending that data and consider NIC teaming to
get higher bandwidth.
Hope this helps.
If the issue is in fact buffer related, you may be able to implement 802.3x flow control which allows the switch to process pause frames sent by the upstream device. This is of course contingent on the upstream device supporting the same function.
See below output as requested.
Transmit GigabitEthernet1/0/4 Receive
309232361 Bytes 945751097 Bytes
2834901126 Unicast frames 1187858761 Unicast frames
47789283 Multicast frames 368291 Multicast frames
83900891 Broadcast frames 2427431 Broadcast frames
0 Too old frames 719529300 Unicast bytes
0 Deferred frames 63614422 Multicast bytes
0 MTU exceeded frames 162607375 Broadcast bytes
0 1 collision frames 0 Alignment errors
0 2 collision frames 0 FCS errors
0 3 collision frames 0 Oversize frames
0 4 collision frames 0 Undersize frames
0 5 collision frames 0 Collision fragments
0 6 collision frames
0 7 collision frames 2416234081 Minimum size frames
0 8 collision frames 4109039079 65 to 127 byte frames
0 9 collision frames 258778270 128 to 255 byte frames
0 10 collision frames 88140508 256 to 511 byte frames
0 11 collision frames 10920577 512 to 1023 byte frames
0 12 collision frames 2897476560 1024 to 1518 byte frames
0 13 collision frames 0 Overrun frames
0 14 collision frames 0 Pause frames
0 15 collision frames
0 Excessive collisions 0 Symbol error frames
0 Late collisions 0 Invalid frames, too large
0 VLAN discard frames 0 Valid frames, too large
0 Excess defer frames 0 Invalid frames, too small
3431800181 64 byte frames 0 Valid frames, too small
1927942576 127 byte frames
2417221874 255 byte frames 0 Too old frames
1047801692 511 byte frames 0 Valid oversize frames
369587019 1023 byte frames 0 System FCS error frames
2362172550 1518 byte frames 0 RxPortFifoFull drop frame
0 Too large frames
0 Good (1 coll) frames
0 Good (>1 coll) frames