Cisco Systems 7401ASR manual Ignored Packets, Router# show interfaces ethernet 0/0

Chapter 5 Troubleshooting

PXF Troubleshooting Information

Packets ignored:		0	ring space:
shadow ring full:		0	shadow ring:			16384
in ring full:		0	inring:			968
PXF inactive:		0
tx credits:	16230330		delayed credits:			0
holdq enqueues:		0	requeue drops:			0
interrupts:		40538	interrupt misses:			1947
interrupt packets:		53326
pending read bytes:		0
Interface	Pkts In	Chars In	Pkts Out	Chars Out	Punted	Dropped
Fa0/0	0	0	30000000	1740000000	970	0
Et1/0	0	0	0	0	21309	0
Et1/1	0	0	0	0	0	0
Et1/2	0	0	0	0	0	0
Et1/3	0	0	0	0	0	0
Se2/0	0	0	0	0	963	0
Se2/1	0	0	0	0	0	0
Se2/2	0	0	0	0	0	0
Se2/3	0	0	0	0	0	0
Fa3/0	0	0	0	0	963	0
PO4/0	30000000	1440000000	0	0	963	0
AT5/0	0	0	0	0	23192	0
Vi1	0	0	0	0	0	0
Vt1	0	0	0	0	0	0
Vi2	0	0	0	0	0	0
Vt2	0	0	0	0	0	0

Note CPU usage becomes more efficient as packet load increases. For example, if you are running at 60% CPU with only 33% of customer load on the system, this does not mean that you need 180% CPU for 100% of customers. Part of the original 60% CPU usage is overhead usage, which does not increase as packet load increases.

Ignored Packets

Packet ignores on an interface may result from high CPU usage. Enter the show interfaces command to display any input ignores:

Router# show interfaces ethernet 0/0

Ethernet0/0 is up, line protocol is up

...

21 input errors, 0 CRC, 0 frame, 0 overrun, 21 ignored

Packets are ignored if there is no available CPU to accept the new packet. This can happen if the router is overloaded with traffic, but can also happen if the interface is faulty. If ignores are present on all interfaces, then the router is probably overloaded with traffic, or does not have sufficient free buffers in the pool that match the maximum transmission unit (MTU) on interfaces. In the latter case, an increment of the ignored counter is followed by an increment of the no buffer counter:

Router# show interfaces serial 0/0

...

1567 packets input, 0 bytes, 22 no buffer

22 input errors, 0 CRC, 0 frame, 0 overrun, 22 ignored, 0 abort

Cisco 7401ASR Installation and Configuration Guide

OL-5419-01 B0 5-9