FastEthernet0/1 is down, line protocol is down (disabled)

SW0#conf tEnter configuration commands, one per line.  End with CNTL/Z.
SW0(config)#int fa0/1
SW0(config-if)#mac-address 0000.0000.0001

04: BW 100000 Kbit, DLY 1000 usec,

Shows the Bandwidth (BW) in Kilobits and delay in micro seconds set on the interface. If this were a router the bandwidth command is used to communicate the capacity of the interface to different routing protocols, which then select the best path through a network.

05: reliability 255/255, txload 1/255, rxload 1/255

Shows the reliability of the interface as a fraction 255/255 is equal to 100% reliability this is calculated as an exponential average over a 5 minute period. txload is transmitted data and rxload is received data, again the display is out of 255 where 1/255 means that the link is practically idle as compared to 128/255 where the interface is handling 50% of traffic. Obviously if either txload or rxload are at 255/255 that means that the interface is completely saturated.

06: Encapsulation ARPA, loopback not set

Shows the encapsulation type set on the interface and whether there is a loopback set. Loopbacks are virtual interfaces that are always up and protocols such as BGP & OSPF make use of them they are a bit like the Windows loopback interface of 127.0.0.1.

07: Keepalive set (10 sec)

Shows the keepalive timer for the interface in seconds. The keepalive is the frequency at which the switch sends messages to itself (Ethernet) or to the other end (Auxiliary) to ensure a network interface is alive.

08: Full-duplex, 100Mb/s

Shows the duplex configured on the interface in this case its full-duplex which allows communication in both directions simultaneously unlike  half-duplex which does not allow simultaneous communication.

09: input flow-control is off, output flow-control is off

Shows the flow control configured on the interfaces. Flow control enables connected Ethernet ports to control traffic rates during congestion by allowing congested nodes to pause link operation at the other end. It does this by sending the remote device a pause frame which when received the remote device stops sending data packets which prevents loss of data packets during the congestion period.

10: ARP type: ARPA, ARP Timeout 04:00:00

Shows the Address Resolution Protocol (ARP) type and the timeout for the protocol. The timeout is the time specified in seconds defining how long a dynamically learned IP address and its corresponding MAC address remain in the ARP cache.

11: Last input 00:00:08, output 00:00:05, output hang never

Shows the last input in the number of hours, minutes and seconds since the last packet was successfully received by an interface. It also shows the output which is the last time the interface successfully transmitted a packet. Output hang never is the time since the interface was last reset because of a transmission that took too long.

12: Last clearing of "show interface" counters never

Shows the last clearing of the show interface counters using the clear counters command.

13: Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Shows the input queue drops. When a packet enters the interface the switch attempts to forward it at interrupt level. If a match cannot be found in an appropriate cache table, the packet is queued on the input queue of the incoming interface to be processed. Some packets are always processed, but with the appropriate configuration and in stable networks, the rate of processed packets must never congest the input queue. If the input queue is full, the packet is dropped.

14: Queueing strategy: fifo

Displays the queuing strategy of the interface. Queuing is the process of sequencing packets before they leave a router interface normally packets leave in the order that they arrive or FIFO (First in first out) when the interface is set to this the interface does not prioritise voice or mission critical traffic.

15: Output queue :0/40 (size/max)

Shows the output queue drops. output drops are caused by a congested interface e.g. the traffic rate on the outgoing interface cannot accept all the packets that should be sent out.

16: 5 minute input rate 0 bits/sec, 0 packets/sec

Shows the input rate of packets for the last 5 minutes.

17: 5 minute output rate 0 bits/sec, 0 packets/sec

Shows the output rate of packets for the last 5 minutes.

18: 956 packets input, 193351 bytes, 0 no buffer

Shows the total amount of packets received on the interface.

19: Received 956 broadcasts, 0 runts, 0 giants, 0 throttles

Shows the amount of broadcasts received on the interface along with the number of Runts (packets with a size of less than 64 bytes and that have a bad CRC Cyclic Redundancy Check). It also shows the number of Giants received (packets that are over the maximum size of an Ethernet frame or over 1518 bytes with a bad FCS Frame Check Sequence). This line also shows the number of Throttles received. Throttles show the number of times the receiver on the port is disabled due to a buffer or processor overload. Throttles can be caused by IP packets with options, expired TTL, non-ARPA encapsulation, fragmentation, tunnelling, ICMP packets, packets with MTU checksum failure, RPF failure, IP checksum and length errors.

20: 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

Shows the number of input errors on the interface. This includes runts, giants, no buffer (the number of packets dropped because there is no free buffer to copy the packet), CRC (Cyclic Redundancy Check), frame, overruns (where the input rate of traffic exceeded the receivers ability to handle the data) and ignored counts (the number of packets ignored by the interface because the interface hardware ran low on internal buffers, this can be caused by broadcast storms and bursts of noise).

21: 0 watchdog, 0 multicast, 0 pause input

Shows the watchdog timeouts on the interface. The watchdog timer controls the time of each process. If the timer is not reset, a trap occurs, if a process is longer than it must be, the watchdog timer is used to escape from this process. It also shows the number of Multicast packets and Pause Input (where the connected device requests for a traffic pause when its receive buffer is almost full)

22: 0 input packets with dribble condition detected

Shows the input packets with dribble condition. A dribble bit error indicates that a frame is slightly too long however the switch will still accept the frame.

23: 2357 packets output, 263570 bytes, 0 underruns

Shows the number of output packets and the underruns on the interface. Underruns are the number of times that the transmitter has been run faster than the switch can handle. This can occur when the interface receives a high volume of bursty traffic from many other interfaces all at once.

24: 0 output errors, 0 collisions, 10 interface resets

Shows the number of output errors. Output errors are the sum of all errors that prevented the final transmission of datagram’s out of the interface. This can be caused by a low output queue size. It also shows the number of collisions on the interface which could be caused by a duplex mismatch. the number of interface resets shows the number of times the interface has been completely reset.

25: 0 babbles, 0 late collision, 0 deferred

Shows the number of babbles on the interface. Babbles indicate the transmit jabber time expired. A Jabber is a frame longer than 1518 octets, which does not end with an even number of octets (alignment error) or has a bad FCS error. It also shows the number of late collisions, late collisions occur when two devices transmit at the same time, and neither side of the connection detects a collision. A common cause of late collisions are the result of incorrect cabling or a non-compliant number of hubs in the network. Bad NICs can also cause late collisions. This line also shows the number of deferred frames, these are frames that have been transmitted successfully after waiting for the media, because the media was busy. This is usually seen in half duplex environments where the carrier is already in use when it tries to transmit a frame. In full duplex environments the issue occurs when the excessive load is destined for the switch.

26: 0 lost carrier, 0 no carrier

Shows the lost carrier counter. This is the number of times the carrier was lost in transmission, causes of this can be a bad cable. The No Carrier counter is the number of times the carrier was not present in the transmission similarly check for a bad cable.

27: 0 output buffer failures, 0 output buffers swapped out

Shows the output buffer failures/swapped out counters. Causes of this are when A port buffers the packets to the Tx buffer when the rate of traffic switched to the port is high and it cannot handle the amount of traffic. The port starts to drop the packets when the Tx buffer is full and thus increases the underruns and the output buffer failure counters. The increase in the output buffer failure counters can be a sign that the ports are run at an inferior speed and/or duplex, or there is too much traffic that goes through the port.