What's the CPU Interface of Switch?

in the 2960-24TT Switch, there is a CPU Interface in it.

Switch#show interfaces | begin CPU
  Hardware is CPU Interface, address is 0002.1669.5897 (bia 0002.1669.5897)
  MTU 1500 bytes, BW 100000 Kbit, DLY 1000000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 21:40:21, output never, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     1682 packets input, 530955 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     563859 packets output, 0 bytes, 0 underruns
     0 output errors, 23 interface resets
     0 output buffer failures, 0 output buffers swapped out

I have two questions:

  1. What's the CPU Interface?
  2. What's the bia meaning there?
  • Is this in packet tracer?
    – user36472
    Nov 9 '18 at 12:35
  • 2
    Each Ethernet interface on a Cisco router has its own Burned in address (BIA) MAC address. Burned-in-address on an interface never changes and you can compare it with what the manufacturer assign to a Network Interface Card on a host.
    – user36472
    Nov 9 '18 at 12:39
  • Did the answer help you? If so, you should accept it so that it doesn't keep popping up. Alternatively, you could provide an answer yourself and accept that.
    – user36472
    Nov 14 '18 at 9:10

It's exactly what it sounds like: the network interface connecting the CPU. It's rarely an actual phy-based NIC; most common is a PCI bus interface to the switch chip(s). It's how managed functions work -- management UI, spanning-tree, etherchannel, routing protocols, CDP/LLDP/etc, etc.

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