Arista Warrior

Chapter 20. LANZ

If you’ve read the chapter on buffers, you know that they can be a benefit or bane, depending on a lot of factors. When buffers in a switch become a problem, it can be very difficult to isolate the problem, since there usually aren’t detailed counters that show the buffer contents. When running QoS on routers, there are all kinds of commands to run that will show you the status of your buffers, but those buffers are software constructs that take memory from the system. The buffers I’m referring to here are hardware switch interface buffers. Let’s dig in and I’ll show you what I mean.

Here’s the output from the show interface command on an Arista 7124SX. As you can see, there is no mention of buffers:

Arista#sho int e5 Ethernet5 is up, line protocol is up (connected) Hardware is Ethernet, address is 001c.7308.80ae Internet address is 10.10.10.5/24 Broadcast address is 255.255.255.255 Address determined by manual configuration MTU 1500 bytes, BW 100000 Kbit Full-duplex, 100Mb/s, auto negotiation: on Up 1 days, 20 hours, 57 minutes, 59 seconds Last clearing of "show interface" counters never 5 minutes input rate 183 bps (0.0% with framing), 0 packets/sec 5 minutes output rate 45 bps (0.0% with framing), 0 packets/sec 828028 packets input, 1130495492 bytes Received 6 broadcasts, 8355 multicast 0 runts, 0 giants 0 input errors, 0 CRC, 0 alignment, 0 symbol 0 PAUSE input 855277 packets output, 1187043452 bytes Sent 3 broadcasts, 8729 multicast 0 output errors, 0 collisions ...