Packets are ignored if there are no free buffers to accept the new packet.
If ignores are present on all interfaces, 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 the interfaces, as shown:
router#show interfaces ethernet 0
Ethernet0/0 is up, line protocol is up
21 input errors, 0 CRC, 0 frame, 0 overrun, 21 ignored
In this case, an increment of the ignored counter is followed by an increment of the no buffer counter, as shown in this sample output:
This interface could be faulty if ignores are only increasing on one interface and are not followed by an increment of the no buffer counter. The interface could also be faulty if the interface is not heavily loaded.
If this is the case, capture the output of the show technical-support command. To open a TAC Service Request for a hardware replacement, refer to the Cisco Technical Assistance Center (TAC) TAC Service Request Tool.
The load on the interface can be viewed in the output of the show interfaces command, as shown in this command output: