Basically when we the rate of traffic switch to a port and it can?t handle the amount of
traffic it will buffer to the packets to Tx buffer when the buffer is full we start drop
the packets and we?ll increase the underruns and output buffer failures counters.
output buffer failures.Description: Cisco IOS sh interfaces counter. The number of failed buffers and the number of buffers swapped out.
Common Causes: As an example, consider a scenario where a 1gig multicast stream is being forwarded to 24 100 Mbps ports. If an egress interface is over-subscribed, it would be normal to see output buffer failures incrementing along with Out-Discards.
Description: The number of times that the transmitter has been running faster than the
switch can handle.
Common Causes: This can occur in a high throughput situation where an interface is being hit with a high volume of bursty traffic from many other interfaces all at once.
Interface resets may be occurring along with the underruns.
To find out whether it is actually caused by over subscription, we can do the following:
Investigate the devices connected to interface
1.Clear the counter then set loading interval to 30 sec and issue the sh interface on ingress port and egress port and see the average traffic going through the links.
2.Use SNMP station to keep polling the ingress and egress interfaces every 5 secs to check the traffic load on ingress and egress ports.
Hello. I know this post has been sitting for awhile, but we are seeing the same problem on a 3550. The interface complaining about all of the output buffer failures and underruns is connected to our providers router, and is only running 10Mb/sec. The provider is only giving us 6Mb to the WAN, so it can't be oversubscription. Also, the 5 minute output rate shows only 2Mb.
We are seeing about 500 output buffer failures/minute, and this is mot during prime usage hours. Could this be a hardware problem?
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...