What is the fifo_overrun counter?

What is the fifo_overrun counter?

Created On 03/29/19 15:24 PM - Last Modified 09/20/22 06:37 AM


Q1. What is the fifo_overrun counter and what causes it to increase?

admin@pa> show system state filter sys.s1.p2.detail | match fifo 
sys.s1.p2.detail: { 'pkts1024tomax_octets': 0x338300d10, 'pkts128to255_octets': 0x38db5149, 'pkts256to511_octets': 0x24eddd47, 'pkts512to1023_octets': 0x20f8656d, 'pkts64_octets': 0x1072a6a19, 'pkts65to127_octets': 0x1293ec46d, 'rcv_fifo_overrun': 0x68bb9, }

Q2. Is there any way to reduce these counters?


Any hardware-based firewall


Answer1: Overruns occur when the buffer of the interface is full, but it is still trying to handle incoming traffic. The port has exceeded its buffer. This is usually due to bursty traffic more than anything else. 

Answer2: There are a few ways to tackle the issue:

1. Upgrade the interface, example from 1 Gig to 10 Gig
2. If it is a single interface, use etherchannel to distribute the load
3. If the interface is already a member of etherchannel, add more interface into it. For a proper load balancing on the interface, use an even number of interfaces (e.g., 2, 4, 6, 8, etc.)

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