Local-Area Networks and LAN Switching - CCIE Routing and Switching Exam Certification Guide - page 108

Foundation Topics

LAN Media Review
This section covers Media Access Control (MAC) addresses, the Ethernet family of data-link
layer technologies, Token Ring, and wireless LANs (WLANs).

MAC Address Format
Ethernet or Token Ring router interfaces and all device network interface cards (NICs) are
identified with a unique burned-in address (BIA) . This is the MAC address , which is also called
the physical address . It is an implementation of Layer 2 of the OSI reference model—or more
specifically, the MAC layer of the IEEE model to identify the station. The MAC address is
48 bits in length (6 octets) and is represented in hexadecimal.

The router output in Example 4-1 shows the MAC address (00-10-7b-3a-92-3c) of an Ethernet
interface.

Router Interface MAC Address

Example 4-1

router> show interface
Ethernet0 is up, line protocol is up
Hardware is Lance, address is 0010.7b3a.923c (bia 0010.7b3a.923c)
Internet address is 135.119.110.30/24
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 1/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue :0/40 (size/max)
5 minute input rate 1000 bits/sec, 2 packets/sec
5 minute output rate 1000 bits/sec, 2 packets/sec
1999164 packets input, 379657585 bytes, 0 no buffer
Received 1785091 broadcasts, 0 runts, 0 giants, 0 throttles
1 input errors, 0 CRC, 0 frame, 0 overrun, 1 ignored
0 input packets with dribble condition detected
745208 packets output, 82211652 bytes, 0 underruns
0 output errors, 63 collisions, 16 interface resets
0 babbles, 0 late collision, 345 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out

0010.7b3a.923c