Packets That Are Smaller Than A Medium's Minimum Packet Size Are Known By What Term Below?

Troubleshooting Ethernet

Ethernet and IEEE 802.3

Full-Duplex Operation 10/100/1000

Autonegotiation

Physical Connections

Frame Formats

Troubleshooting Ethernet

evidence interfaces ethernet

Syntax Description

Command Way

Usage Guidelines

Sample Display

Troubleshooting Ethernet

Ethernet was developed by Xerox Corporation's Palo Alto Inquiry Center (PARC) in the 1970s. Ethernet was the technological ground for the IEEE 802.3 specification, which was initially released in 1980. Before long thereafter, Digital Equipment Corporation, Intel Corporation, and Xerox Corporation jointly developed and released an Ethernet specification (Version ii.0) that is substantially uniform with IEEE 802.3. Together, Ethernet and IEEE 802.3 currently maintain the greatest marketplace share of any local-surface area network (LAN) protocol. Today, the term Ethernet is often used to refer to all carrier sense multiple access standoff detect (CSMA/CD) LANs that by and large arrange to Ethernet specifications, including IEEE 802.3.

When it was adult, Ethernet was designed to fill the heart ground between long-distance, low-speed networks and specialized, computer-room networks carrying information at loftier speeds for very express distances. Ethernet is well suited to applications on which a local communication medium must bear sporadic, occasionally heavy traffic at loftier peak information rates.

Ethernet and IEEE 802.3

Ethernet and IEEE 802.iii specify like technologies. Both are CSMA/CD LANs. Stations on a CSMA/CD LAN can access the network at whatever fourth dimension. Before sending information, CSMA/CD stations "listen" to the network to see if information technology is already in use. If it is, the station wanting to transmit waits. If the network is not in use, the station transmits. A collision occurs when two stations mind for network traffic, "hear" none, and transmit simultaneously. In this example, both transmissions are damaged, and the stations must retransmit at some later time. Back-off algorithms determine when the colliding stations retransmit. CSMA/CD stations can observe collisions, so they know when they must retransmit. This access method is used by traditional Ethernet and IEEE 802.3 functions in half-duplex style. (When Ethernet is operated in total-duplex mode, CSMA/CD is non used.) This means that only i station can transmit at a time over the shared Ethernet.

This access method was conceived to offer shared and fair access to multiple network stations/devices. It allows these systems fair access to the Ethernet network through a process of arbitration by dictating how stations fastened to this network can access the shared channel. Information technology allows stations to listen earlier transmitting and tin recover if signals collide. This recovery time interval is chosen a slot time and is based on the circular-trip fourth dimension that it takes to transport a 64-byte frame the maximum length of an Ethernet LAN attached by repeaters. Another name for this shared LAN is a collision domain. For half-duplex operation, the mode on which traditional Ethernet is based, the size of your collision domain can be limited by the concrete limitations of the cabling utilized. Tabular array four-one lists the collision domains for 10/100/1000 Mbps.

Table 4-1 Examples of Traditional Ethernet and IEEE 802.3 Collision Domains
Traditional Ethernet and 802.three Collision Domains
Signaling Speed	Network Diameter
10BaseX	About 280 meters (coax)	Ethernet
10/100BaseX	Well-nigh 205 meters (twisted pair)	IEEE 802.3b
1000BaseX	About xx meters (fiber and copper)	IEEE 802.3z

The limitations of the cable itself can create even smaller boundaries.

Because the 64-byte slot time is consequent for 10/100/thou transmission speeds, this severely limits the scalability for 1000BaseX to operate in a network with a bore of more than 20 meters. To overcome this obstacle, use carrier extension $.25 in addition to the Ethernet frame size to extend the time that transmits on the wire. This expands the network diameter to 100 meters per segment, like 100BaseT.

For this arrangement to piece of work, everyone must abide by the same rules. For CSMA/CD the rules are equally follows:

1. Listen—Stations mind for signals on the wire. If a signal is detected (carrier sense), then stations should not endeavour to transmit frame. If a station "hears" another indicate on the wire while transmitting the first 64 bytes of a frame, it should recognize that its frame has collided with another.

2. Standoff detect—If a station detects a collision, it must dorsum off from sending the frame using the truncated dorsum-off algorithm. The back-off algorithm counts the number of collisions, if any, to decide how long a station must wait to retransmit the frame. This algorithm backs off each time that a collision is detected. The goal of this method is to provide the system a way to determine how many stations are trying to transmit simultaneously and and so guess when it should be safe to effort again. The style that the truncated back-off algorithm tracks and adjusts timers is based on the value of 2north , where n is the number of collisions encountered during manual of the frame. The result is a estimate of how many stations may exist on the shared channel. This outcome gets plugged in as a range, counting from zip, for the number of slot times to wait. The algorithm randomly selects a value from this range equally shown in Tabular array four-two.

Table 4-two Back-off Algorithm
2due north value¹	Actions
20-1	Stations either attempt to retransmit immediately or look for one slot time.
2two	Stations randomly expect cypher, i, ii, or three slot times to retransmit.
two3	Stations randomly wait from zero to seven slot times.
24	. . . you lot get the point.

^oneiin where due north = the number of collisions

Depending on the number of collisions the algorithm randomly selects to dorsum off, a station could potentially look a while before retransmitting.

The algorithm standoff counter stops incrementing at ten, where the penalty await time is selected from a range of 0 to 1023 slot times before retransmission. This is pretty bad, only the algorithm will endeavor to retransmit the frame up to xvi collisions. Then it just gives up, and a college-layer network protocol such as TCP/IP will attempt to retransmit the parcel. This is an indication that you have some serious errors.

When a station successfully sends a frame, the standoff counter (penalty) is cleared (for that frame) and no loner must wait for the back-off time. ("Interface" statistics are not cleared, just the timer is). Any stations with the everyman collisions will exist capable of accessing the wire more chop-chop because they practice non have to wait.

Both Ethernet and IEEE 802.three LANs are broadcast networks. In other words, all stations encounter all frames, regardless of whether they represent an intended destination. Each station must examine received frames to determine whether the station is a destination. If it is a destination, the frame is passed to a higher protocol layer for appropriate processing.

Differences between Ethernet and IEEE 802.3 standards are subtle. Ethernet provides services respective to Layers i and two of the OSI reference model, whereas IEEE 802.3 specifies the physical layer (Layer i) and the aqueduct-access portion of the link layer (Layer ii), only does not define a logical link control protocol. Both Ethernet and IEEE 802.3 are implemented in hardware. Typically, the physical manifestation of these protocols is either an interface carte in a host reckoner or circuitry on a primary circuit board within a host estimator.

Now, having said all that regarding the regular operation of traditional Ethernet and 802.3, we must discuss where the two split up in features and functionality. The IEEE 802.iii standard was based on traditional Ethernet, simply improvements have been fabricated to this current standard. What we have discussed so far will non scale in today'south demanding service provider and enterprise networks.

Full-Duplex Operation ten/100/1000

Everything y'all've read so far dealt with one-half-duplex functioning (CSMA/CD, dorsum-off timers, so on). Total-duplex mode allows stations to transmit and receive data simultaneously. This makes for more efficient utilise of the available bandwidth past allowing open access to the medium. Conversely, this way of operation tin can function only with Ethernet switching hubs or via Ethernet cross-over cables between interfaces capable of total-duplex Ethernet. Total-duplex mode expects links to be point-to-point links. There are also no collisions in full-duplex fashion, so CSMA/CD is not needed.

Autonegotiation

Autonegotiation allows Ethernet devices to automatically configure their interfaces for operation. If the network interfaces supported different speeds or unlike modes of operation, they volition attempt to settle on a lower mutual denominator. A plain repeater cannot support multiple speeds; it knows only how to regenerate signals. Smart hubs employ multiple repeaters and a switch plane internally to let stations that support different speeds to communicate. The negotiation is performed only when the system initially connects to the hub. If slower systems are fastened to the aforementioned smart hub, and so faster systems volition accept to be manually configured for x Mbps performance.

To brand sure that your connectedness is operating properly, IEEE 802.iii Ethernet employs normal link pulses (NLPs), which are used for verifying link integrity in a 10BaseT organisation. This signaling gives y'all the link indication when you attach to the hub and is performed between two straight continued link interfaces (hub-to-station or station-to-station). NLPs are helpful in determining that a link has been established betwixt devices, but they are not a skillful indicator that your cabling is free of problems.

An extension of NLPs is fast link pulses. These do not perform link tests, only instead are employed in the autonegotiation process to advertise a device'south capabilities. Autonegotiation on 1000BaseX networks works at only 1000 Mbps, so the simply feature "negotiated" is for full- or half-duplex operation. In that location may be new vendor implementations on the marketplace that can autonegotiate speeds 10 to 1000BaseX, but at this time they are non widely deployed.

A backup alternative, called parallel detection, works for 10/100 speeds if autonegotiation is disabled or is unsupported. This is basically a fallback machinery that springs into action when autonegotiation fails. The interface capable of autonegotiation will configure itself for bare bones ten-Mbps half-duplex functioning.

Physical Connections

IEEE 802.3 specifies several different physical layers, whereas Ethernet defines only one. Each IEEE 802.three physical layer protocol has a name that summarizes its characteristics. The coded components of an IEEE 802.3 physical layer proper noun are shown in Figure iv-1.

Effigy 4-1 IEEE 802.3 Concrete Layer Proper name Components

A summary of Ethernet Version 2 and IEEE 802.3 characteristics appears in Tables 4-3 and 4-4.

Table iv-3 Ethernet Version ii and IEEE 802.iii Physical Characteristics
Characteristic	Ethernet Value	IEEE 802.3 Values
Characteristic	Ethernet Value	10Base5	10Base2	1Base5	10BaseT	10Broad36
Data charge per unit (Mbps)	x	10	10	1	10	10
Signaling method	Baseband	Baseband	Baseband	Baseband	Baseband	Broadband
Maximum segment length (g)	500	500	185	250	100	1800
Media	fifty-ohm coax (thick)	50-ohm coax (thick)	50-ohm coax (sparse)	Unshielded twisted- pair wire	Unshielded twisted- pair wire	75-ohm coax
Topology	Passenger vehicle	Bus	Coach	Star	Star	Star

Table four-4 IEEE 802.3 Physical Characteristics
Characteristic	IEEE 802.3 Values
Characteristic	10BaseFX	1000BaseFX
Information rate (Mbps)	100	1000
Signaling method	Baseband	Baseband
Maximum segment length (m)	Repeater 150 m; full-duplex 2000 m Single style up to six to 10 km	Repeater 150 thousand; total-duplex 2000 g Single fashion upwardly to half dozen to 10 km
Media	Fiber (single way or multimode)	Fiber (unmarried mode or multimode)
Topology	Star	Star

There are other 100Basen implementations, but they are non widely implemented for diverse reasons. One particular instance in signal is 100BaseT4. This system uses four pairs of copper wire and can be used on voice- and information-class cablevision. ten/100BaseT systems perform well on Category 5 information-grade cable and use but two pairs of copper wire.

Ethernet is nearly similar to IEEE 802.3 10Base5. Both of these protocols specify a bus topology network with a connecting cablevision between the stop stations and the bodily network medium. In the case of Ethernet, that cable is chosen a transceiver cable. The transceiver cable connects to a transceiver device attached to the physical network medium. The IEEE 802.iii configuration is much the same, except that the connecting cable is referred to equally an attachment unit interface (AUI), and the transceiver is called a media attachment unit (MAU). In both cases, the connecting cable attaches to an interface board (or interface circuitry) within the end station.

Frame Formats

Ethernet and IEEE 802.3 frame formats are shown in Figure iv-two.

Figure 4-2 Ethernet and IEEE 802.3 Frame Formats

Both Ethernet and IEEE 802.3 frames brainstorm with an alternating pattern of ones and zeros called a preamble. The preamble tells receiving stations that a frame is coming.

The byte earlier the destination address in both an Ethernet and an IEEE 802.3 frame is a start-of-frame (SOF) delimiter. This byte ends with two consecutive 1 bits, which serve to synchronize the frame reception portions of all stations on the LAN.

Immediately post-obit the preamble in both Ethernet and IEEE 802.3 LANs are the destination and source address fields. Both Ethernet and IEEE 802.3 addresses are 6 bytes long. Addresses are contained in hardware on the Ethernet and IEEE 802.3 interface cards. The first three bytes of the addresses are specified by the IEEE on a vendor-dependent basis, and the last 3 bytes are specified by the Ethernet or IEEE 802.3 vendor. The source address is e'er a unicast (unmarried node) address, whereas the destination accost may be unicast, multicast (group), or broadcast (all nodes).

In Ethernet frames, the 2-byte field following the source address is a blazon field. This field specifies the upper-layer protocol to receive the data subsequently Ethernet processing is complete.

In IEEE 802.iii frames, the ii-byte field post-obit the source address is a length field, which indicates the number of bytes of data that follow this field and precede the frame check sequence (FCS) field.

Post-obit the type/length field is the actual data contained in the frame. After physical layer and link layer processing is consummate, this data will eventually be sent to an upper-layer protocol. In the case of Ethernet, the upper-layer protocol is identified in the type field. In the instance of IEEE 802.iii, the upper-layer protocol must be defined inside the information portion of the frame, if at all. If data in the frame is insufficient to make full the frame to its minimum 64-byte size, padding bytes are inserted to ensure at least a 64-byte frame.

In 802.3 the data field carries a payload header in addition to the payload itself. This header serves the logical link control sublayer of the OSI model and is completely independent of the MAC sublayer and physical layer below information technology. This header, functionally known equally 802.two encapsulation, contains destination service access point (DSAP) and source service access signal (SSAP) information. This will notify higher protocols what type of payload is really riding in the frame. It functions like the "type" field in traditional Ethernet and is used by upper-layer network protocols such equally IPX. Network software developed to support the TCP/IP networking suite uses the type field to determine protocol type in an Ethernet frame. The type field and the LLC header are non replacements for each other, but they serve to offer backward compatibility between network protocol implementations without rewriting the entire Ethernet frame.

After the information field is a 4-byte frame cheque sequence (FCS) field containing a cyclic redundancy check (CRC) value. The CRC is created by the sending device and is recalculated past the receiving device to check for damage that might have occurred to the frame in transit.

Troubleshooting Ethernet

Tabular array 4-v provides troubleshooting procedures for common Ethernet media bug.

Table 4-5 Troubleshooting Procedures for Common Ethernet Media Problems
Media Problem	Suggested Actions
Excessive dissonance	one. Apply the show interfaces ethernet exec command to determine the status of the router's Ethernet interfaces. The presence of many CRC errors merely not many collisions is an indication of excessive noise. 2. Check cables to determine whether whatever are damaged. iii. Look for badly spaced taps causing reflections. 4. If you are using 100BaseTX, make certain you are using Category five cabling and non some other type, such as Category iii.
Excessive collisions	1. Utilise the evidence interfaces ethernet command to bank check the rate of collisions. The total number of collisions with respect to the full number of output packets should be around 0.i percent or less. 2. Use a TDR to observe any unterminated Ethernet cables. 3. Look for a jabbering transceiver fastened to a host. (This might crave host-past-host inspection or the utilise of a protocol analyzer.)
Excessive runt frames	In a shared Ethernet surround, runt frames are almost always caused by collisions. If the standoff rate is high, refer to the problem of excessive collisions, earlier in this tabular array. If runt frames occur when collisions are not high or when in a switched Ethernet environment, and so they are the result of underruns or bad software on a network interface menu. Utilise a protocol analyzer to try to determine the source address of the runt frames.
Tardily collisions	1. Use a protocol analyzer to bank check for tardily collisions. Belatedly collisions should never occur in a properly designed Ethernet network. They usually occur when Ethernet cables are also long or when there are as well many repeaters in the network. 2. Check the diameter of the network, and brand certain that it is inside specification.
No link integrity on 10BaseT, 100BaseT4, or 100BaseTX	1. Make sure that you are non using 100BaseT4 when simply two pairs of wire are available. 100BaseT4 requires four pairs. 2. Check for a 10BaseT, 100BaseT4, or 100BaseTX mismatch (for example, a menu different from the port on a hub). three. Determine whether there is cross-connect. (For case, exist sure that straight-through cables are not being used between a station and the hub.) four. Check for excessive dissonance (see the problem of excessive noise, earlier in this table).

When you're troubleshooting Ethernet media in a Cisco router environment, the show interfaces ethernet control provides several key fields of information that can assist with isolating problems. The following section provides a detailed description of the show interfaces ethernet control and the information that it provides.

evidence interfaces ethernet

Use the show interfaces ethernet privileged exec control to brandish data nigh an Ethernet interface on the router:

•show interfaces ethernet unit [bookkeeping]

• bear witness interfaces ethernet [slot | port] [bookkeeping] (for the Cisco 7200 series and Cisco 7500)

• show interfaces ethernet [type slot | port-adapter | port] (for ports on VIP cards in the Cisco 7500 series routers)

Syntax Description

unit—This must lucifer a port number on the selected interface.

bookkeeping—(Optional) This displays the number of packets of each protocol blazon that have been sent through the interface.

slot—Refer to the appropriate hardware manual for slot and port information.

port—Refer to the appropriate hardware manual for slot and port information.

port-adapter—Refer to the appropriate hardware transmission for data about port adapter compatibility.

Command Mode

Privileged exec

Usage Guidelines

This control offset appeared in Cisco IOS Release x.0. If you do non provide values for the argument unit (or slot and port on the Cisco 7200 series, or slot and port-adapter on the Cisco 7500 series), the control will display statistics for all network interfaces. The optional keyword bookkeeping displays the number of packets of each protocol type that have been sent through the interface.

Sample Display

The following is sample output from the show interfaces command for the Ethernet 0 interface:

Router# bear witness interfaces ethernet 0

Ethernet 0 is upwardly, line protocol is upwardly

            Hardware is MCI Ethernet, address is aa00.0400.0134 (via 0000.0c00.4369)

            Cyberspace address is 131.108.ane.1, subnet mask is 255.255.255.0

            MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/255, load 1/255

            Encapsulation ARPA, loopback non fix, keepalive set (ten sec)

            ARP type: ARPA, PROBE, ARP Timeout 4:00:00

            Last input 0:00:00, output 0:00:00, output hang never

            Output queue 0/40, 0 drops; input queue 0/75, two drops

            Five minute input rate 61000 bits/sec, iv packets/sec

            Five minute output rate 1000 $.25/sec, 2 packets/sec

            2295197 packets input, 305539992 bytes, 0 no buffer

            Received 1925500 broadcasts, 0 runts, 0 giants

            3 input errors, three CRC, 0 frame, 0 overrun, 0 ignored, 0 arrest

            0 input packets with dribble condition detected

            3594664 packets output, 436549843 bytes, 0 underruns

            viii output errors, 1790 collisions, x interface resets, 0 restarts

Table 4-6 presents bear witness interfaces ethernet field descriptions.

Tabular array iv-6 show interfaces ethernet Field Descriptions
Field	Description
Ethernet . . . is up . . . is administratively down	Indicates whether the interface hardware is currently active and whether information technology has been taken down by an administrator. "Disabled" indicates that the router has received more than than 5,000 errors in a keepalive interval, which is 10 seconds, past default.
line protocol is {up \| downwards \| administratively downwards}	Indicates whether the software processes that handle the line protocol believe that the interface is usable (that is, whether keepalives are successful) or if it has been taken down by an administrator.
Hardware	Specifies the hardware blazon (for example, MCI Ethernet, SCI, cBus Ethernet) and accost.
Internet accost	Specifies the Internet address, followed past the subnet mask.
MTU	Gives the maximum transmission unit of measurement of the interface.
BW	Gives the bandwidth of the interface in kilobits per 2nd.
DLY	Gives the delay of the interface in microseconds.
rely	Shows reliability of the interface as a fraction of 255 (255/255 is 100 percent reliability), calculated equally an exponential average over v minutes.
load	Shows load on the interface as a fraction of 255 (255/255 is completely saturated), calculated equally an exponential average over five minutes.
Encapsulation	Specifies the encapsulation method assigned to interface.
ARP blazon	Specifies the type of Accost Resolution Protocol assigned.
loopback	Indicates whether loopback is set.
keepalive	Indicates whether keepalives are gear up.
Last input	Gives the number of hours, minutes, and seconds since the concluding packet was successfully received by an interface. This is useful for knowing when a dead interface failed.
Last output	Gives the number of hours, minutes, and seconds since the last packet was successfully transmitted by an interface.
output	Gives the number of hours, minutes, and seconds since the last parcel was successfully transmitted past the interface. This is useful for knowing when a dead interface failed.
output hang	Gives the number of hours, minutes, and seconds (or never) since the interface was last reset because of a transmission that took too long. When the number of hours in any of the "final" fields exceeds 24 hours, the number of days and hours is printed. If that field overflows, asterisks are printed.
Final clearing	Gives the time at which the counters that measure out cumulative statistics (such as number of bytes transmitted and received) shown in this report were final reset to zero. Annotation that variables that might affect routing (for example, load and reliability) are not cleared when the counters are cleared. "***" indicates that the elapsed time is as well large to exist displayed. "0:00:00" indicates that the counters were cleared more than than 231ms (and less than 232ms) ago.
Output queue, input queue, drops	Gives the number of packets in output and input queues. Each number is followed by a slash, the maximum size of the queue, and the number of packets dropped due to a total queue.
V minute input charge per unit, 5 minute output charge per unit	Gives the average number of bits and packets transmitted per second in the past 5 minutes. If the interface is not in promiscuous style, it senses network traffic information technology sends and receives (rather than all network traffic). The five-minute input and output rates should be used only every bit an approximation of traffic per 2nd during a given 5-minute period. These rates are exponentially weighted averages with a fourth dimension constant of 5 minutes. A period of iv time constants must pass earlier the boilerplate will be inside 2 percent of the instantaneous charge per unit of a uniform stream of traffic over that period.
packets input	Gives the total number of error-free packets re ceived past the organization.
bytes input	Gives the full number of bytes, including data and MAC encapsulation, in the fault-free packets received by the system.
no buffers	Gives the number of received packets discarded considering at that place was no buffer space in the primary system. Compare this with the ignored count. Broadcast storms on Ethernet networks and bursts of noise on serial lines are often responsible for no input buffer events.
Received . . . broadcasts	Shows the total number of broadcast or multicast packets received by the interface.
Runts	Gives the number of packets that are discarded because they are smaller than the medium's minimum packet size. For instance, any Ethernet parcel that is less than 64 bytes is considered a runt.
giants	Gives the number of packets that are discarded because they exceed the medium's maximum packet size. For example, any Ethernet packet that is greater than 1518 bytes is considered a giant.
input error	Includes runts, giants, no buffer, CRC, frame, overrun, and ignored counts. Other input-related errors can too cause the input error count to be increased, and some datagrams may take more ane error; therefore, this sum may not balance with the sum of enumerated input mistake counts.
CRC	Indicates that the cyclic redundancy checksum generated by the originating LAN station or far-finish device does not match the checksum calculated from the data received. On a LAN, this normally indicates racket or transmission issues on the LAN interface or the LAN double-decker itself. A loftier number of CRCs is usually the outcome of collisions or a station transmitting bad data.
frame	Shows the number of packets received incorrectly having a CRC fault and a noninteger number of octets. On a LAN, this is usually the upshot of collisions or a malfunctioning Ethernet device.
overrun	Shows the number of times that the receiver hardware was incapable of handing received data to a hardware buffer considering the input rate exceeded the receiver'southward capability to handle the data.
ignored	Shows the number of received packets ignored by the interface because the interface hardware ran low on internal buffers. These buffers are dissimilar from the arrangement buffers mentioned previously in the buffer description. Broadcast storms and bursts of noise tin cause the ignored count to exist increased.
input packets with dribble condition detected	Gives the dribble bit error, which indicates that a frame is slightly also long. This frame error counter is incremented only for informational purposes; the router accepts the frame.
packets output	Shows the total number of messages transmitted past the system.
bytes	Shows the total number of bytes, including data and MAC encapsulation, transmitted past the organisation.
underruns	Gives the number of times that the transmitter has been running faster than the router can handle. This may never be reported on some interfaces.
output errors	Gives the sum of all errors that prevented the last transmission of datagrams out of the interface being examined. Notation that this may non rest with the sum of the enumerated output errors because some datagrams may have more than one error, and others may take errors that do not autumn into whatsoever of the specifically tabulated categories.
collisions	Gives the number of messages retransmitted due to an Ethernet collision. This is ordinarily the upshot of an overextended LAN (Ethernet or transceiver cablevision also long, more than ii repeaters between stations, or too many cascaded multiport transceivers). A packet that collides is counted just once in output packets.
interface resets	Gives the number of times that an interface has been completely reset. This can happen if packets queued for transmission were not sent within several seconds. On a serial line, this tin be caused past a malfunctioning modem that is non supplying the transmit clock point, or by a cablevision trouble. If the system notices that the carrier discover line of a serial interface is up, but the line protocol is downward, information technology periodically resets the interface in an endeavour to restart it. Interface resets can also occur when an interface is looped dorsum or shut down.
restarts	Gives the number of times a Type 2 Ethernet controller was restarted because of errors.