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This chapter describes how to configure and maintain the interfaces supported on the protocol translator. You will find information about enabling, shutting down, and displaying statistics about the following interfaces:
You will also find information about configuring the null interface and the Point-to-Point Protocol (PPP) in this chapter.
To enable an interface, you must be in the configuration command collection mode. To enter this mode, type the EXEC command configure at the EXEC prompt. Once in the command collection mode, start configuring the interface by entering the interface command. Once an interface is configured, you can check its status by entering EXEC show commands at the EXEC prompt.
This chapter provides software configuration information only. For hardware technical
descriptions and for information about installing these interfaces, refer to the hardware reference and maintenance publication for your particular product.
Summaries of the interface configuration commands and EXEC monitoring commands described in this chapter are included at the end of the chapter.
The interface command is entered in configuration mode and identifies a specific network interface (for example, a serial port, Ethernet port, or a Token Ring port). By entering this command you begin the command collection mode for the specified interface.
The interface command has the following syntax:
interface type unitThe argument type identifies the interface type and the argument unit identifies the connector or interface card number. Unit numbers are assigned at the factory at the time of installation, or when added to a system, and can be displayed with the show interfaces command.
This example begins interface configuration command collection mode for serial connector zero (interface serial 0).
interface serial 0
Use the EXEC command show interfaces (described later in this chapter) to determine the interface type and unit numbers.
In the interface configuration command collection mode, you enter the interface subcommands for your particular routing or bridging protocol. The interface configuration command collection mode ends when you enter a command that is not an interface subcommand, or when you type the Ctrl-Z sequence.
To add a descriptive name to an interface, use the description interface subcommand.
description name-stringThe argument name-string is text, or a description to help you remember what is attached to this interface. The description command is meant solely as a comment to be put in the configuration to help you remember what certain interfaces are used for. The description will appear in the output of the following commands: show configuration, write terminal, and show interfaces.
This example describes a 3174 controller on serial 0.
interface serial 0 description 3174 Controller for test lab
You disable an interface using the shutdown interface subcommand. The full syntax for this command follows:
shutdown The shutdown command disables all functions on the specified interface. The command also marks the interface as unavailable. On serial interfaces, this command causes the DTR signal to be dropped. On Token Ring interfaces, this command causes the interface to be
de-inserted from the ring.
To restart a disabled interface, use the no shutdown interface subcommand.
To check whether an interface is disabled, use the EXEC command show interfaces as described in the next section. An interface that has been shut down is shown as administratively down in the display from this command.
These commands turn off the interface Ethernet 0:
interface ethernet 0 shutdown
These commands turn the interface back on:
interface ethernet 0 no shutdown
To clear the interface counters shown with the show interfaces command, enter the following command at the EXEC prompt:
clear counters [type unit]The command clears all the current interface counters from the interface unless the optional arguments type and unit are specified to clear only a specific interface type (serial, Ethernet, Token Ring, and so on) from a specific unit or card number.
The Cisco software contains commands that you can enter at the EXEC prompt to display different information about the interface including the version of the software and the hardware, the controller status, and some statistics about the different interfaces. These commands begin with the word "show." (The full list of these commands can be displayed by entering the command show ? at the EXEC prompt.) A description of interface-specific show commands follows.
The show controllers command displays current internal status information for different interface cards. Enter this command at the EXEC prompt:
show controllers {serial|token|mci}Use the following keywords to display the information about that card:
Sample output for the MCI controller card follows. Table 1-1 describes the fields seen.
pt> show controllers mci
MCI 0, controller type 1.1, microcode version 1.8
128 Kbytes of main memory, 4 Kbytes cache memory
22 system TX buffers, largest buffer size 1520
Restarts: 0 line down, 0 hung output, 0 controller error
Interface 0 is Ethernet0, station address 0000.0c00.d4a6
15 total RX buffers, 11 buffer TX queue limit, buffer size 1520
Transmitter delay is 0 microseconds
Interface 1 is Serial0, electrical interface is V.35 DTE
15 total RX buffers, 11 buffer TX queue limit, buffer size 1520
Transmitter delay is 0 microseconds
High speed synchronous serial interface
Interface 2 is Ethernet1, station address aa00.0400.3be4
15 total RX buffers, 11 buffer TX queue limit, buffer size 1520
Transmitter delay is 0 microseconds
Interface 3 is Serial1, electrical interface is V.35 DCE
15 total RX buffers, 11 buffer TX queue limit, buffer size 1520
Transmitter delay is 0 microseconds
High speed synchronous serial interface
| Field | Description |
|---|---|
| MCI (number) | The unit number of the MCI card |
| controller type | The version number of the MCI card |
| microcode version | The version number of the MCI card's internal software (in read-only memory) |
| main memory cache memory | The amount of main and cache memory on the cache memory card |
| system TX | Number of buffers that hold packets to be transmitted |
| Restarts line down hung output controller error | Count of restarts due to the following conditions: Communication line down Output unable to transmit Internal error |
| interface..is | Names of interfaces, by number |
| electrical interface | Line interface type for serial connections |
| RX buffers | Number of buffers for received packets |
| TX queue limit | Maximum number of buffers in transmit queue |
| Transmitter delay | Delay between outgoing frames |
| Station address | The hardware address of the interface |
The Cisco software also provides the show interfaces command which displays statistics for the network interfaces on the network server. Enter this command at the EXEC prompt:
show interfaces [type unit]Specify the optional arguments type and unit to display statistics for a particular network interface. The argument type can be one of the following: ethernet, serial, or tokenring. Use the argument unit to specify the interface unit number.
You will use the show interfaces command frequently while configuring and monitoring your modules.
For further explanations and examples about a specific interface, refer to the following sections in this chapter: "Monitoring the Serial Interface" "Monitoring the Ethernet Interface" and "Monitoring the Token Ring Interface"
Support for the serial interface is supplied on one of Cisco Systems' serial network interface cards:
The high-speed synchronous serial interface is also supported on the IGS network server.
To specify a serial interface, use this configuration command:
interface serial unitSpecify the serial interface connector number with the argument unit.
Follow this command with the interface subcommands for your particular protocol or
application as described in the chapters in Part Five.
The SCI and MCI cards can query the appliques to determine their types. However, they do so only at system startup, so the appliques must be attached when the system is started. Issue a show controllers serial or show controllers mci command to determine how the serial card (either MCI or SCI) has identified them. The command will also show the capabilities of the serial card and report controller-related failures.
This command begins configuration on interface serial 0.
interface serial 0
The serial interfaces support the following kinds of serial encapsulations:
The HDLC and PPP encapsulation methods are described in this chapter. The Frame Relay encapsulation method is described in the "Frame Rleay Configuration and Management" chapter, the SMDS encapsulation in the "SMDS Configuration and Management" chapter, and the X.25 and LAPB encapsulation methods in the "X.25 Configuration and Management" chapter.
The encapsulation method is changed by using the interface configuration subcommand encapsulation followed by a keyword that defines the encapsulation method.
encapsulation encapsulation-typeThe encapsulation-type argument is a keyword that identifies one of the following serial encapsulation types that Cisco Systems' software supports:
Cisco provides HDLC serial encapsulation for serial lines. This encapsulation method provides the synchronous framing and error detection functions of HDLC without windowing or retransmission. Although HDLC is the default serial encapsulation method, it can be re-installed using the hdlc keyword with the encapsulation command as follows:
encapsulation hdlcUse the command clear interface to reset the hardware logic on an interface. Enter this command at the EXEC prompt:
clear interface serial unitThe argument unit specifies the serial part number. In this case, the argument type is serial.
Use the command show interfaces serial to display information about the serial interface and the state of source bridging. Enter this command at the EXEC prompt:
show interfaces serial [unit]The argument unit is the interface unit number. If you do not provide values for the unit argument, the command will display statistics for all the network interfaces.
Sample output of this command for Cisco's synchronous serial interfaces is provided below: Table 1-2 describes the fields seen.
pt>show interfaces serial 0Serial 0 is up, line protocol is up Hardware is MCI Serial Internet address is 150.136.190.203, subnet mask is 255.255.255.0 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec) Last input 0:00:07, output 0:00:00, output hang never Output queue 0/40, 0 drops; input queue 0/75, 0 drops Five minute input rate 0 bits/sec, 0 packets/sec Five minute output rate 0 bits/sec, 0 packets/sec 16263 packets input, 1347238 bytes, 0 no buffer Received 13983 broadcasts, 0 runts, 0 giants 2 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 2 abort 22146 packets output, 2383680 bytes, 0 underruns 0 output errors, 0 collisions, 2 interface resets, 0 restarts 1 carrier transitions
| Field | Description |
|---|---|
| Serial ... is {up |down} ...is administratively down | Tells whether the interface hardware is currently active (whether carrier detect is present) and if it has been taken down by an administrator. |
| line protocol is {up | down | administratively down} | Tells whether the software processes that handle the line protocol think the line is usable (are keepalives successful?). |
| Hardware is | Specifies the hardware type. |
| Internet address is | Specifies the Internet address and subnet mask, followed by packet size. |
| MTU | Maximum Transmission Unit of the interface. |
| BW | Bandwidth of the interface in kilobits per second. |
| DLY | Delay of the interface in microseconds. |
| rely | Reliability of the interface as a fraction of 255 (255/255 is 100% reliability), calculated as an exponential average over five minutes. |
| load | Load on the interface as a fraction of 255 (255/255 is completely saturated), calculated as an exponential average over five minutes. |
| Encapsulation | Encapsulation method assigned to interface. |
| loopback | Tells whether loopback is set or not. |
| keepalive | Tells whether keepalives are set or not. |
| Last input | The number of hours, minutes, and seconds since the last packet was successfully received by an interface. Useful for knowing when a dead interface failed. |
| output hang | 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 "last" fields exceeds 24 hours, the number of days and hours is printed. If that field overflows, asterisks are printed. |
| Output queue, Input Queue, drops | 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 full queue. |
| Five minute input rate, Five minute output rate | The average number of bytes and packets transmitted per second in the last five minutes. |
| packets input | The total number of error-free packets received by the system. |
| broadcasts | The total number of broadcast or multicast packets received by the interface. |
| runts | The number of packets that are discarded because they are smaller than the medium's minimum packet size. |
| giants | The number of packets that are discarded because they exceed the medium's maximum packet size. |
| input error | The total number of no buffer, runts, giants, CRCs, frame, overrun, ignored, and abort counts. Other input-related errors can also increment the count, so that this sum may not balance with the other counts. |
| CRC | The Cyclic Redundancy Checksum generated by the originating station or far-end device does not match the checksum calculated from the data received. On a serial link, CRCs usually indicate noise, gain hits, or other transmission problems on the data link. |
| frame | The number of packets received incorrectly having a CRC error and a noninteger number of octets. On a serial line, this is usually the result of noise or other transmission problems. |
| overrun | The number of times the serial receiver hardware was unable to hand received data to a hardware buffer because the input rate exceeded the receiver's ability to handle the data. |
| ignored | The number of received packets ignored by the interface because the interface hardware ran low on internal buffers. These buffers are different than the system buffers mentioned previously in the buffer description. Broadcast storms and bursts of noise can cause the ignored count to be increased. |
| abort | An illegal sequence of one bits on a serial interface. This usually indicates a clocking problem between the serial interface and the data link equipment. |
| packets output | Total number of messages transmitted by the system. |
| bytes output | Total number of bytes, including data and MAC encapsulation, transmitted by the system. |
| underruns | Number of times that the transmitter has been running faster than the server can handle. This may never happen (be reported) on some interfaces. |
| output errors | The sum of all errors that prevented the final transmission of datagrams out of the interface being examined. Note that this may not balance with the sum of the enumerated output errors, as some datagrams may have more than one error, and others may have errors that do not fall into any of the specifically tabulated categories. |
| interface resets | The number of times an interface has been completely reset. This can happen if packets queued for transmission were not sent within several seconds' time. On a serial line, this can be caused by a malfunctioning modem which is not supplying the transmit clock signal, or by a cable problem. If the system notices that the carrier detect line of a serial interface is up, but the line protocol is down, it periodically resets the interface in an effort to restart it. Interface resets can also occur when an interface is looped back down. |
| restarts | The number of times the controller was restarted because of errors. |
| carrier transitions | The number of times the carrier detect signal of a serial interface has changed state. Indicates modem or line problems if the carrier detect line is changing state often. |
An interface configured for PPP encapsulation differs from the standard show interface serial output in the fourth and fifth lines displayed. An interface configured for PPP might include the following information.
Encapsulation PPP, loopback not set, keepalive set (10 sec)
Use the commands debug serial-interface and debug serial-packet to debug serial interface events. The EXEC commands are as follows:
debug serial-interfaceUse debug serial-packet for detailed debugging information, and debug serial-interface for more general information.
Use the undebug serial-interface and undebug serial-packets to turn off messaging from these debug commands.
Support for the Ethernet interface is supplied on one of Cisco Systems' Ethernet network interface cards:
The Ethernet interface is also supported on the IGS network server.
To specify an Ethernet interface, use this configuration command:
interface ethernet unitSpecify the Ethernet interface connector number with the argument unit.
Follow this command with the interface subcommands for your particular protocol or
application as described in the chapters in Part Five.
This command begins configuration on interface Ethernet 1.
interface ethernet 1
The Ethernet interface supports a number of encapsulation methods. These methods are assigned by using the interface subcommand encapsulation followed by a keyword that defines the encapsulation method. The particular encapsulation method used depends on the protocol. Currently, there are three common Ethernet encapsulation methods:
The syntax of the encapsulation command follows:
encapsulation encapsulation-typeThe encapsulation-type is one of the following three keywords:
These commands enable standard Ethernet Version 2.0 encapsulation on interface
Ethernet 0.
interface ethernet 0 encapsulation arpa
Use the command clear interface to reset the hardware logic on an interface. Enter this command at the EXEC prompt:
clear interface ethernet unitThe argument unit specifies the Ethernet port number.
Use the command show interfaces ethernet to display information about the Ethernet interface. Enter this command at the EXEC prompt:
show interfaces ethernet [unit]The argument unit is the interface unit number. If you do not provide values for the unit argument, the command will display statistics for all the network interfaces.
Sample output of this command is provided on the following page. Table 1-3 describes the fields seen.
pt>show interfaces ethernet 0Ethernet 0 is up, line protocol is up Hardware is MCI Ethernet, address is aa00.0400.0134 (bia 0000.0c00.4369) Internet address is 131.108.1.1, 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 not set, keepalive set (10 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, 2 drops Five minute input rate 61000 bits/sec, 4 packets/sec Five minute output rate 1000 bits/sec, 2 packets/sec 2295197 packets input, 305539992 bytes, 0 no buffer Received 1925500 broadcasts, 0 runts, 0 giants 3 input errors, 3 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 3594664 packets output, 436549843 bytes, 0 underruns 8 output errors, 1790 collisions, 10 interface resets, 0 restarts
| Field | Description |
|---|---|
| Ethernet ... is up ...is administratively down | Tells whether the interface hardware is currently active and if it has been taken down by an administrator. |
| line protocol is {up | down | administratively down} | Tells whether the software processes that handle the line protocol believe the interface is usable (are keepalives successful?). |
| Hardware | Specifies the hardware type (for example, MCI Ethernet, cBus Ethernet) and address. |
| Internet address | Lists the Internet address followed by subnet mask. |
| MTU | Maximum Transmission Unit of the interface. |
| BW | Bandwidth of the interface in kilobits per second. |
| DLY | Delay of the interface in microseconds. |
| rely | Reliability of the interface as a fraction of 255 (255/255 is 100% reliability), calculated as an exponential average over five minutes. |
| load | Load on the interface as a fraction of 255 (255/255 is completely saturated), calculated as an exponential average over five minutes. |
| Encapsulation | Encapsulation method assigned to interface. |
| ARP type: | Type of Address Resolution Protocol assigned. |
| loopback | Tells whether loopback was set or not. |
| output | Number of hours, minutes, and seconds (or never) since the last packet was successfully transmitted by the interface. Useful for knowing when a dead interface failed. |
| output hang | 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 "last" fields exceeds 24 hours, the number of days and hours is printed. If that field overflows, asterisks are printed. |
| Last Clearing | The time at which the counters that measure cumulative statistics (such as number of bytes transmitted and received) shown in this report were last reset to zero. Note that variables that might affect routing (for example, load and reliability) are not cleared when the counters are cleared. |
| Output queue, Input queue, drops | 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 full queue. |
| Five minute input rate, Five minute output rate | The average number of bytes and packets transmitted per second in the last five minutes. |
| packets input | The total number of error-free packets received by the system. |
| Received ..broadcasts | The total number of broadcast or multicast packets received by the interface. |
| runts | The number of packets that are discarded because they are smaller than the medium's minimum packet size. For instance, any Ethernet packet which is less than 64 bytes is considered a runt. |
| giants | The number of packets that are discarded because they exceed the medium's maximum packet size. For example, any Ethernet packet which 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 also cause the input errors count to be increased, and some datagrams may have more than one error; therefore, this sum may not balance with the sum of enumerated input error counts. |
| CRC | The Cyclic Redundancy Checksum generated by the originating LAN station or far-end device does not match the checksum calculated from the data received. On a LAN, this usually indicates noise or transmission problems on the LAN interface or the LAN bus itself. A high number of CRCs is usually the result of collisions or a station transmitting bad data. |
| frame | The number of packets received incorrectly having a CRC error and a noninteger number of octets. On a LAN, this is usually the result of collisions or a malfunctioning Ethernet device. |
| overrun | The number of times the serial receiver hardware was unable to hand received data to a hardware buffer because the input rate exceeded the receiver's ability to handle the data. |
| ignored | The number of received packets ignored by the interface because the interface hardware ran low on internal buffers. These buffers are different than the system buffers mentioned previously in the buffer description. Broadcast storms and bursts of noise can cause the ignored count to be increased. |
| packets output | Total number of messages transmitted by the system. |
| bytes | Total number of bytes, including data and MAC encapsulation, transmitted by the system. |
| underruns | Number of times that the transmitter has been running faster than the router can handle. This may never happen (be reported) on some interfaces. |
| output errors | The sum of all errors which prevented the final transmission of datagrams out of the interface being examined. Note that this may not balance with the sum of the enumerated output errors, as some datagrams may have more than one error, and others may have errors that do not fall into any of the specifically tabulated categories. |
| collisions | The number of messages retransmitted due to an Ethernet collision. This is usually the result of an overextended LAN (Ethernet or transceiver cable too long, more than two repeaters between stations, or too many cascaded multiport transceivers). A packet that collides is counted only once in output packets. |
| interface resets | The number of times an interface has been completely reset. This can happen if packets queued for transmission were not sent within several seconds time. Interface resets can also occur when an interface is looped back or shut down. |
| restarts | The number of times a Type 2 Ethernet controller was restarted because of errors. |
Use the command debug broadcast to debug MAC broadcast packets. Enter this command at the EXEC prompt.
debug broadcastUse the undebug broadcast command to turn off messaging.
Use the command debug packet to enable a log of packets that the network is unable to classify. Examples of this are packets with unknown link type, or IP packets with an unrecognized protocol field. Enter this command at the EXEC prompt.
debug packetUse the undebug packet command to turn off messaging.
Support for the Token Ring interface is supplied on one of Cisco Systems' Token Ring network interface cards:
The Cisco Token Ring interface supports both routing (Level 3 switching) and source-route bridging (Level 2 switching).
To configure a Token Ring interface, use this configuration command:
interface tokenring unitSpecify the card number with the argument unit.
Follow this command with the interface subcommands for your particular protocol or application as described in the chapters in Part Five.
This command begins configuration on the first Token Ring interface.
interface tokenring 0
The Token Ring interface on the IGS/TR can run at either 4 or 16 Mbps. This speed is software selectable. The IGS/TR does not default to any particular ring speed. This speed must be provided the first time the IGS/TR is put to use.
 | Caution Configuring a ring speed that is wrong or incompatible with the connected Token Ring will cause the ring to beacon, which effectively takes the ring down and makes it nonoperational. |
Use the ring-speed interface subcommand to set ring speed for an IGS/TR Token Ring interface. The command syntax follows:
ring-speed speedThe argument speed can be either 4 or 16. When specified as 4, ring speed is set for 4-Mbps operation; when specified to 16, ring speed is set for 16-Mbps operation. The default is 16.
The following commands set an IGS/TR Token Ring interface ring speed to 4 Mbps.
interface tokenring 0 ring-speed 4
Cisco's Token Ring interface by default uses the SNAP encapsulation format defined in RFC 1042. It is not necessary to define an encapsulation method for this interface.
Use the command clear interface to reset the hardware logic on an interface. Enter this command at the EXEC prompt:
clear interface token ring unitThe arguments unit specifies the Token Ring card number.
To maintain the Routing Information Field (RIF) cache for protocol translators with Token Ring interfaces, use the clear rif-cache command. The command syntax is:
clear rif-cacheThis command clears all entries from the RIF cache. It applies only to Token Ring interfaces.
Use the command show interface to display information about the Token Ring interface and the state of source bridging. Enter this command at the EXEC prompt:
show interfaces tokenring [unit]The argument unit is the interface unit number.
Sample output of this command is provided below. Table 1-4 describes the fields seen.
pt> show interfaces tokenring 0
TokenRing 0 is up, line protocol is up
Hardware is 16/4 Token Ring, address is 5500.2000.dc27 (bia 0000.3000.072b)
Internet address is 150.136.230.203, subnet mask is 255.255.255.0
MTU 8136 bytes, BW 16000 Kbit, DLY 630 usec, rely 255/255, load 1/255
Encapsulation SNAP, loopback not set, keepalive set (10 sec)
ARP type: SNAP, ARP Timeout 4:00:00
Ring speed: 16 Mbps
Single ring node, Source Route Bridge capable
Group Address: 0x00000000, Functional Address: 0x60840000
Last input 0:00:01, output 0:00:01, output hang never
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
Five minute input rate 0 bits/sec, 0 packets/sec
Five minute output rate 0 bits/sec, 0 packets/sec
16339 packets input, 1496515 bytes, 0 no buffer
Received 9895 broadcasts, 0 runts, 0 giants
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
32648 packets output, 9738303 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets, 0 restarts
5 transitions
| Field | Description |
|---|---|
| Token Ring is up | down | The interface is currently active and inserted into ring (up) or inactive and not inserted (down). |
| Token Ring is Reset | Hardware error has occurred. |
| Token Ring is Initializing | Hardware is up, in the process of inserting the ring. |
| Token Ring is Administratively Down | Hardware has been taken down by an administrator. |
| line protocol is {up | down | administratively down} | Tells whether the software processes that handle the line protocol believe the interface is usable (are keepalives successful?). |
| Hardware | Specifies the hardware type (Token Ring or 16/4 Token Ring) and provides the address. |
| Internet address | Lists the Internet address followed by subnet mask. |
| MTU | Maximum Transmission Unit of the interface. |
| BW | Bandwidth of the interface in kilobits per second. |
| DLY | Delay of the interface in microseconds. |
| rely | Reliability of the interface as a fraction of 255 (255/255 is 100% reliability), calculated as an exponential average over five minutes. |
| load | Load on the interface as a fraction of 255 (255/255 is completely saturated), calculated as an exponential average over five minutes. |
| Encapsulation | Encapsulation method assigned to interface. |
| loopback | Tells whether loopback is set or not. |
| keepalive | Tells whether keepalives are set or not. |
| ARP type: | Type of Address Resolution Protocol assigned. |
| Ring speed: | Speed of Token Ring -- 4 or 16 Mbps. |
| {Single ring | multiring node} | Indicates whether a node is enabled to collect and use source routing information (RIF) for routable Token Ring protocols. |
| Group Address: | The interface's group address, if any. The group address is a multicast address; any number of interfaces on the ring may share the same group address. Each interface may have at most one group address. |
| Last input | The number of hours, minutes, and seconds since the last packet was successfully received by an interface. Useful for knowing when a dead interface failed. |
| output hang | 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 "last" fields exceeds 24 hours, the number of days and hours is printed. If that field overflows, asterisks are printed. |
| Output queue, Input Queue, drops | 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 full queue. |
| Five minute input rate, Five minute output rate | The average number of bytes and packets transmitted per second in the last five minutes. |
| packets input | The total number of error-free packets received by the system. |
| broadcasts | The total number of broadcast or multicast packets received by the interface. |
| runts | The number of packets that are discarded because they are smaller than the medium's minimum packet size. |
| giants | The number of packets that are discarded because they exceed the medium's maximum packet size. |
| CRC | The Cyclic Redundancy Checksum generated by the originating LAN station or far-end device does not match the checksum calculated from the data received. On a LAN, this usually indicates noise or transmission problems on the LAN interface or the LAN bus itself. A high number of CRCs is usually the result of a station transmitting bad data. |
| frame | The number of packets received incorrectly having a CRC error and a noninteger number of octets. |
| overrun | The number of times the serial receiver hardware was unable to hand received data to a hardware buffer because the input rate exceeded the receiver's ability to handle the data. |
| ignored | The number of received packets ignored by the interface because the interface hardware ran low on internal buffers. These buffers are different than the system buffers mentioned previously in the buffer description. Broadcast storms and bursts of noise can cause the ignored count to be increased. |
| packets output | Total number of messages transmitted by the system. |
| bytes output | Total number of bytes, including data and MAC encapsulation, transmitted by the system. |
| underruns | Number of times that the far-end transmitter has been running faster than the near-end server's receiver can handle. This may never happen (be reported) on some interfaces. |
| output errors | The sum of all errors that prevented the final transmission of datagrams out of the interface being examined. Note that this may not balance with the sum of the enumerated output errors, as some datagrams may have more than one error, and others may have errors that do not fall into any of the specifically tabulated categories. |
| collisions | Since a Token Ring cannot have collisions, this statistic is nonzero only if an unusual event occurred when frames were being queued or dequeued by the system software. |
| interface resets | The number of times an interface has been reset. The interface may be reset by the administrator or automatically when an internal error occurs. |
| restarts | Should always be zero for Token Ring interfaces. |
| transitions | The number of times the ring made a transition from up to down, or vice versa. A large number of transitions indicates a problem with the ring or the interface. |
Use the EXEC commands described in this section to troubleshoot the Token Ring interface.
Use the debug rif command to enable logging of route information.
debug rifThe command enables logging of information about the route information fields (RIF) in Token Ring packets.
Use the debug token-event command to enable logging of Token Ring events.
debug token-eventThis command provides a display of low-volume output.
Use the EXEC command debug token-ring to display messages about the Token Ring interface activity. This command reports several lines of information for each packet sent or received and is intended for low traffic, detailed debugging.
debug token-ringThe Token Ring interface records detailed information regarding the current state of the ring. These messages are only displayed when debug token-event is enabled.
Enter the undebug command with the appropriate keyword to turn off the messages.
The last ring status message is displayed in the EXEC command show interfaces display for a Token Ring interface. Table 1-5 describes the messages displayed by this command.
The Point-to-Point Protocol (PPP) is a method of encapsulating Internet Protocol (IP) datagrams and other Network Layer protocol information over point-to-point links. The document "Point-to-Point Initial Configuration Options" defines the set of options that are negotiated during startup.
Of the possible upper layer protocols, only IP is supported at this time. Thus, the only upper-level protocol that can be sent or received over a point-to-point link using PPP encapsulation is IP.
The Point-to-Point Protocol is enabled on an interface using the encapsulation interface subcommand followed by the ppp keyword.
encapsulation pppThese commands enable PPP encapsulation on serial interface zero.
interface serial 0 encapsulation ppp
Access control using Challenge Handshake Authentication Protocol (CHAP) is available on all serial interfaces. The authentication feature will reduce the risk of security violations on your protocol translator. The Cisco implementation of CHAP is supported by PPP encapsulation only.
When CHAP is enabled, a remote device (a PC, workstation, router, or communication server) attempting to connect to the local protocol translator is requested, or challenged, to respond. The required response is an encrypted version of a secret password, or secret, plus a random value and the name of the remote device. This name must be configured as described in the "Configuring Host Name Authentication" section later in this chapter.
By transmitting this response, the secret is never transmitted, preventing other devices from stealing it and gaining illegal access to the system. Without the proper response, the remote device cannot connect to the local protocol translator.
CHAP transactions occur only at the time a link is established. The local protocol translator does not request a password during the rest of the call. (The local protocol translator can, however, respond to such requests from other devices during a call.)
The Cisco implementation of CHAP does not suppor the callback option. (The callback option requires that the called router hang up and return the call to a preconfigured telephone number.)
To use CHAP, you must perform the following steps, which are described later in this section.
Step 1: Enable CHAP on the interface.
Step 2: Configure server authentication.
CHAP is specified in the IETF draft "The PPP Authentication Protocols" by Brian Lloyd of Lloyd and Associates and William A. Simpson of Computer Systems Consulting Services. The latest version is dated December 1991.
CHAP is specified as an additional authentication phase of the PPP Link Control Protocol.
To enable CHAP on the interface, use this command:
ppp authentication chapOnce you have enabled CHAP, the local protocol translator requires a password from remote devices. If the remote device does not support CHAP, no traffic will be passed to that device.
Configure the secret using the following command:
username name password secretFor each remote system that the local protocol translator requires authentication from, you add a username entry.
The name argument is the host name of either the local protocol translator or a remote device.
The secret argument specifies the secret for the local protocol translator or the remote device. If there is no secret specified and debug serial-interface is enabled, an error is displayed when a link is established. Debugging information on CHAP is available using the debug serial-interface and debug serial-packet commands.
The secret is encrypted when it is stored on the local protocol translator. This prevents the secret from being stolen. The secret can consist of any string of up to eleven printable ASCII characters. There is no limit to the number of username/password combinations that can be specified, allowing any number of remote devices to be authenticated using CHAP.
The following example configuration enables CHAP on interface serial 0. It also defines a password for the local server, XXX and a remote server,YYY.
hostname XXXinterface serial 0encapsulation pppppp authentication chapusername XXX password oursystemusername YYY password theirsystem
Cisco provides support for a null interface. This pseudo-interface functions similarly to the null devices available on most operating systems. This interface is always up and can never forward or receive traffic; encapsulation always fails.
The null interface provides an alternative method of filtering traffic. The overhead involved with using access lists can be avoided by directing undesired network traffic to the null interface.
To specify the null interface, specify "null 0" (or "null0") as the interface name and unit. The null interface may be used in any command that has an interface type as a parameter.
This command configures a null interface for IP route 127.0.0.0.
ip route 127.0.0.0 null 0
Following are alphabetically arranged summaries of the interface subcommands for interface support.
[no] description name-string
Adds a descriptive name to an interface. The argument name-string is a comment to be put in the configuration.
encapsulation encapsulation-type
Assigns encapsulation method. The encapsulation-type argument is a keyword that identifies one of the following serial encapsulation types that Cisco Systems' software supports:
interface type unit
Specifies a serial interface. The argument type specifies the interface type--serial, ethernet, or tokenring--and the argument unit specifies the interface number or card number.
ring-speed speed
Sets operational ring speed for interface.
The argument speed can be either 4 or 16. When specified as 4, ring speed is set for
4-Mbps operation; when specified to 16, ring speed is set for 16-Mbps operation. The default is 16.
[no] shutdown
Disables and enables an interface.
Following is an alphabetically arranged summary of the EXEC interface support commands.
Resets all interface counters listed in show interface statistics. The arguments type and unit specify the interface type and unit or card number (such as, ethernet 0, serial 0, or tokenring 0).
Resets the hardware logic on an interface. The arguments type and unit specify the interface type and unit or card number (such as, ethernet 0, serial 0, or tokenring 0).
Maintains the Routing Information Field (RIF) cache for protocol translators with a Token Ring interface. This command clears all entries from the RIF cache. It applies only to protocol translators with Token Ring interfaces.
Enables you to log all Level 2 (MAC) broadcast packets received. This information is useful for finding the source of a broadcast storm.
Enables logging of packets that the network server is unable to classify. Examples of this are packets with an unknown Ethernet link type, or IP packets with an unrecognized protocol field.
Enables logging of route information about the route information fields (RIF) in Token Ring packets.
Enables general logging of serial-interface events for network servers equipped with serial network interfaces.
Enables detailed logging of serial-interface events for network servers equipped with serial network interfaces.
Enables logging of Token Ring events and provides a display of low-volume output.
Enables logging of Token Ring interface activity. This command reports several lines of information for each packet sent or received and is intended for low traffic, detailed debugging.
show controllers {serial|token|mci}
Displays current internal status information for different interface cards.
Displays statistics for the network interfaces on the network server. The optional argument type can be one of the following: ethernet, serial, or tokenring. The argument unit specifies the interface unit or card number.
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