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Cisco 7100 Series VPN Router Installation and Configuration Guide
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Chapter 1 Overview
Functional Overview
You can also use arguments such as the interface type (Ethernet, Token Ring, ATM, and so
forth) and the slot/port number to display information about a specific interface only.
The following example shows the display for the fixed LAN (Fast Ethernet interface) port 0
in slot 0:
Router#
show interfaces fastethernet 0/0
FastEthernet0/0 is up, line protocol is up
Hardware is DEC21140A, address is 0050.73ff.6300 (bia 0050.73ff.6300)
Internet address is 10.0.0.0/1
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
reliablility 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half-duplex, 10Mb/s, 100BaseTX/FX
ARP type:ARPA, ARP Timeout 04:00:00
Last input 00:00:04, output 00:00:03, output hang never
Last clearing of "show interface" counters never
Queueing strategy:fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 2000 bits/sec, 1 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
134 packets input, 41451 bytes
Received 134 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast
0 input packets with dribble condition detected
26 packets output, 5281 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
For information on the other commands used to configure the router, refer to the Cisco IOS configuration
guides and command references, which are available on the Documentation CD-ROM or in print.
MAC Addresses
The Media Access Control (MAC) or hardware address is a standardized data-link layer address that is
required for certain network interface types. These addresses are not used by other devices in the
network; they are specific and unique to each port. The router uses a specific method to assign and
control the MAC addresses of its port adapters.
All LAN interfaces (ports) require unique MAC addresses. Typically, the MAC address of an interface
is stored on a memory component that resides directly on the interface circuitry; however, the online
insertion and removal (OIR) feature requires a different method. (For a description of OIR, see
“Online
Insertion and Removal” section on page 1-33
.)
The OIR feature allows you to remove a port adapter and replace it with another identically configured
one. If the new port adapter matches the port adapter you removed, the system immediately brings it on
line. To allow OIR, an address allocator with unique MAC addresses is stored in an EEPROM on the
router. Each address is reserved for a specific port and slot in the router regardless of whether a port
adapter resides in that slot. The MAC addresses are assigned to slot 3 in Cisco 7120 series routers and
slot 4 in Cisco 7140 series routers. This address scheme allows you to remove a port adapter and insert
the port adapter into other routers without causing the MAC addresses to move around the network or
be assigned to multiple devices.
