|
|
Use the commands in this chapter to configure Link Access Procedure Balanced (LAPB), X.25, DDN X.25, and Blacker Front End (BFE). X.25 provides remote terminal access; encapsulation for the IP, DECnet, XNS, ISO CLNS, AppleTalk, Novell IPX, Banyan VINES, and Apollo Domain protocols; and bridging. X.25 virtual circuits may also be switched between interfaces (local routing), between two router (remote routing or tunneling), and over non-serial media (CMNS).
To translate between X.25 and another protocol, refer to the Protocol Translator Configuration Guide and Command Reference publication.
For X.25 and LAPB configuration information and examples, refer to the "Configuring X.25 and LAPB" chapter in the Router Products Configuration Guide.
To allow the router to participate in emergency mode or to end participation in emergency mode when the interface is configured for x25 bfe-emergency decision and x25 bfe-decision ask, use the bfe EXEC command.
bfe {enter | leave} type number
enter | Causes the router to send a special address translation packet that includes an enter emergency mode command to the BFE if the emergency mode window is open. If the BFE is already in emergency mode, this command enables the sending of address translation information. |
leave | Disables the sending of address translation information from the router to the BFE when the BFE is in emergency mode. |
type | Interface type. |
number | Interface number. |
EXEC
The following example enables an interface to participate in BFE emergency mode:
bfe enter serial 0
encapsulation x25
x25 bfe-decision
x25 bfe-emergency
To clear switched virtual circuits (SVCs) and to reset permanent virtual circuits (PVCs), use the clear x25-vc privileged EXEC command. To clear all X.25 virtual circuits at once by restarting the packet layer service, use this command without an lcn argument.
clear x25-vc type number [lcn]
type | Interface type. |
number | Interface number. |
lcn | (Optional) Virtual circuit. |
Privileged EXEC
The following example illustrates how to clear all virtual circuits on an interface:
clear x25-vc serial 1
To enable Connection-Mode Network Service (CMNS) on a nonserial interface, use the cmns enable interface configuration command. To disable this capability, use the no form of this command.
cmns enableThis command has no arguments or keywords.
The CMNS protocol is implicitly enabled whenever an X.25 encapsulation command is included with a serial interface configuration. A particular nonserial interface, however, must be explicitly configured to use CMNS.
Interface configuration
After processing this command on the LAN interfaces (Ethernet, FDDI, and Token Ring), all the X.25-related interface configuration commands are made available.
The following example enables CMNS on interface Ethernet 0:
interface ethernet 0 cmns enable
To exchange datagrams over a serial interface using LAPB encapsulation, use the encapsulation lapb interface configuration command.
encapsulation lapb [dte | dce] [multi | protocol]
dte | (Optional) Specifies operation as a DTE. This is the default LAPB mode. |
dce | (Optional) Specifies operation as a DCE. |
multi | (Optional) Specifies use of multiple local-area network (LAN) protocols to be carried on the LAPB line. |
protocol | (Optional) A single protocol to be carried on the LAPB line. A single protocol can be one of the following: apollo, appletalk, clns (ISO CLNS), decnet, ip, ipx (Novell IPX), vines, and xns. IP is the default protocol. |
The default serial encapsulation is HDLC. You must explicitly configure a LAPB encapsulation method.
DTE operation is the default LAPB mode. IP is the default protocol.
Interface configuration
LAPB encapsulations are appropriate only for private connections, where you have complete control over both ends of the link. Connections to X.25 networks should use an x25 encapsulation configuration, which operates the X.25 Layer 3 protocol above a LAPB Layer 2.
One end of the link must be a logical DCE and the other end a logical DTE. (This assignment is independent of the interface's hardware DTE/DCE identity.)
Both ends of the LAPB link must specify the same protocol encapsulation.
LAPB encapsulation is supported on serial lines configured for dial-on-demand (DDR) routing. It can be configured on DDR synchronous serial and ISDN interfaces and on DDR dialer rotary groups. It is not supported on asynchronous dialer interfaces.
A single-protocol LAPB encapsulation exchanges datagrams of the given protocol, each in a separate LAPB information frame. You should configure the interface with the protocol-specific parameters needed (for example, a link that carries IP traffic will have an IP address defined for the interface).
A multiprotocol LAPB encapsulation can exchange any or all of the protocols allowed for a single-protocol interface. It also exchanges datagrams, each in a separate LAPB information frame, although two bytes of protocol identification data precede the protocol data. You should configure the interface with all of the protocol-specific parameters needed for each protocol carried.
Beginning with Cisco IOS Release 10.3, LAPB encapsulation supports the priority and custom queueing features.
The following example sets the operating mode as DTE and specifies that AppleTalk protocol traffic will be carried on the LAPB line:
interface serial 1 encapsulation lapb dte appletalk
To specify an interface's operation as an X.25 device, use the encapsulation x25 interface configuration command.
encapsulation x25 [dte | dce] [ddn | bfe] | [ietf]
dte | (Optional) Specifies operation as a DTE. This is the default X.25 mode. |
dce | (Optional) Specifies operation as a DCE. |
ddn | (Optional) Specifies DDN encapsulation on an interface using DDN X.25 standard service |
bfe | (Optional) Specifies BFE encapsulation on an interface attached to a Blacker Front End device. Available for BFE operation only. |
ietf | (Optional) Specifies that the interface's datagram encapsulation should default to use of the IETF standard method, as defined by RFC 1356. |
The default serial encapsulation is HDLC. You must explicitly configure an X.25 encapsulation method.
DTE operation is the default X.25 mode. Cisco's traditional X.25 encapsulation method is the default.
Interface configuration
One end of an X.25 link must be a logical DCE and the other end a logical DTE. (This assignment is independent of the interface's hardware DTE/DCE identity.) Typically, when connecting to a public data network (PDN), the customer equipment acts as the DTE and the PDN attachment acts as the DCE.
Cisco has supported the encapsulation of a number of datagram protocols for quite some time, using a standard means when available and proprietary means when necessary. More recently the IETF adopted a standard, RFC 1356, for encapsulating most types of datagram traffic over X.25. X.25 interfaces use Cisco's traditional method unless explicitly configured for IETF operation; if the ietf keyword is specified, that standard will be used unless Cisco's traditional method is explicitly configured. For details see the x25 map command.
When an X.25 interface is reconfigured, all of the interface's X.25 parameters are initialized except the x25 map commands. The x25 map statements that are configured for an interface are not deleted when the encapsulation is changed, so they will be retained if the interface is later reconfigured for X.25 operation.
A router attaching to the Defense Data Network (DDN) or to a Blacker Front End (BFE) device can be configured to use their respective algorithms to convert between IP and X.121 addresses by using the ddn or bfe options, respectively. An IP address should be assigned to the interface, from which the algorithm will generate the interface's X.121 address; for proper operation, this X.121 address should not be modified.
A router DDN attachment can operate as either a DTE or a DCE device. A BFE attachment can operate only as a DTE device. The ietf option is not available if either the ddn or bfe option is selected.
The following example configures the interface for connection to a Blacker Front End device:
interface serial 0 encapsulation x25 bfe
To specify a period during which a link will remain connected, even if a brief hardware outage occurs, use the lapb interface-outage interface configuration command.
lapb interface-outage milliseconds
milliseconds | Number of milliseconds a hardware outage can last without having the protocol disconnect the service. The default is 0 milliseconds, which disables this feature. |
0 milliseconds, which disables this feature.
Interface configuration
If a hardware outage lasts longer than the LAPB hardware outage period you select, normal protocol operations will occur. The link will be declared to be down and, when it is restored, a link set up will be initiated.
The following example sets the interface outage period to 100 milliseconds. The link will remain connected for outages equal to or shorter than that period.
encapsulation lapb dte ip lapb interface-outage 100
To specify the maximum permissible number of outstanding frames, called the window size, use the lapb k interface configuration command.
lapb k window-size
window-size | Frame count. It can be a value from 1 to the modulo size minus 1 (the maximum is 7 if the modulo size is 8; it is 127 if the modulo size is 128). The default is 7 frames. |
7 frames
Interface configuration
If the window size is changed while the protocol is up, the new value will take effect only when the protocol is reset. You will be informed that the new value will not take effect immediately.
When using the LAPB modulo 128 mode (extended mode), the window parameter k should be increased to make use of the ability to send a larger number of frames before acknowledgment is required. This is the basis for its ability to achieve greater throughput on high speed links that have a low error rate.
This configured value should match the value configured in the peer X.25 switch. Nonmatching values will cause repeated LAPB REJ frames.
The following example sets the LAPB window size (the k parameter) to ten frames:
interface serial 0 lapb modulo
lapb k 10
To specify the LAPB basic (modulo 8) or extended (modulo 128) protocol mode, use the lapb modulo interface configuration command.
lapb modulo modulus
modulus | Either 8 or 128. The value 8 specifies LAPB's basic mode; the value 128 specifies LAPB's extended mode. The default is 8. |
Modulo 8
Interface configuration
The modulo parameter determines which of LAPB's two modes is to be used. The modulo values derive from the fact that basic mode numbers information frames between 0 and 7, whereas extended mode numbers them between 0 and 127. Basic mode is widely available and is sufficient for most links. Extended mode is an optional LAPB feature that may achieve greater throughput on high-speed links that have a low error rate.
The LAPB operating mode may be set on X.25 links as well as LAPB Links. The X.25 modulo is independent of the LAPB layer modulo. Both ends of a link must use the same LAPB mode.
When using modulo 128 mode, the window parameter k should be increased to make use of the ability to send a larger number of frames before acknowledgment is required. This is the basis for its ability to achieve greater throughput on high-speed links that have a low error rate.
If the modulo value is changed while the protocol is up, the new value will take effect only when the protocol is reset. The operator will be informed that the new value will not take effect immediately.
The following example configures a high-speed X.25 link to use LAPB's extended mode:
interface serial 1 encapsulation x25 lapb modulo 128 lapb k 40 clock rate 2000000
To specify the maximum number of bits a frame can hold (the LAPB N1 parameter), use the lapb n1 interface configuration command.
lapb n1 bits
bits | Maximum number of bits in multiples of eight. The minimum and maximum range is dynamically set. Use the ? to view the range. |
The largest (maximum) value available for the particular interface is the default. The Cisco IOS software dynamically calculates n1 whenever you change the maximum transmission unit (MTU), the L2/L3 modulo, or compression on a LAPB interface.
Interface configuration
This command first appeared in Cisco IOS Release 10.0.
 | Caution The LAPB n1 parameter provides little benefit beyond the interface MTU and can easily cause link failures if misconfigured. Cisco recommends that this parameter be left at its default value. |
The Cisco IOS software uses the following formula to determine the minimum n1 value:
The Cisco IOS software uses the following formula to determine for the maximum n1 value:
LAPB overhead is 2 bytes for modulo 8 and 3 bytes for modulo 128.
X.25 overhead is 3 bytes for modulo 8 and 4 bytes for modulo 128.
You need not set n1 to an exact value to support a particular X.25 data packet size. The n1 parameter prevents the processing of any huge frames that result from a "jabbering" interface, an unlikely event.
In addition, the various standards bodies specify that n1 be given in bits rather than bytes. While some equipment can be configured in bytes or will automatically adjust for some of the overhead information present, Cisco devices are configured using the true value, in bits, of n1.
You cannot set the n1 parameter to a value less than that required to support an X.25 data packet size of 128 bytes. All X.25 implementations must be able to support 128-byte data packets. Moreover, if you configure n1 to be less than 2104 bits, you receive a warning message that X.25 might have problems because some nondata packets can use up to 259 bytes.
You cannot set the n1 parameter to a value larger than the default unless the hardware MTU size is first increased.
The X.25 software will accept default packet sizes and CALLs that specify maximum packet sizes greater than what the LAPB layer will support, but will negotiate the CALLs placed on the interface to the largest value that can be supported. For switched CALLs, the packet size negotiation takes place end-to-end through the Cisco router so the CALL will not have a maximum packet size that exceeds the capability of either of the two interfaces involved.
The following example shows how to use the ? command to display the minimum and maximum n1 value. In this example, X.25 encapsulation has both the LAPB and X.25 modulo set to 8. Any violation of this n1 range results in an "Invalid input" error message.
interface serial 1 lapb n1 ? <1080-12056> LAPB N1 parameter (bits; multiple of 8)
The following example sets the N1 bits to 16440:
interface serial 0
lapb n1 16440 mtu 2048
A dagger (†) indicates that the command is documented in another chapter.
mtu†
To specify the maximum number of times a data frame can be transmitted (the LAPB N2 parameter), use the lapb n2 interface configuration command.
lapb n2 tries
tries | Transmission count. It can be a value from 1 through 255. The default is 20 transmissions. |
20 transmissions
Interface configuration
The following example sets the N2 tries to 50:
interface serial 0
lapb n2 50
Use the lapb protocol interface configuration command to configure the protocol carried on the LAPB line.
lapb protocol protocol
protocol | Protocol, entered by keyword. It can be one of the following: appletalk, apollo, clns (ISO CLNS), decnet, ip, ipx (Novell IPX), vines, and xns. |
IP
Interface configuration
This command is not available when using a multiprotocol LAPB encapsulation.
The following example sets AppleTalk as the only protocol on the LAPB line:
interface serial 1 encapsulation lapb
lapb protocol appletalk
encapsulation lapb
encapsulation lapb-dce
encapsulation lapb-multi
To set the retransmission timer period (the LAPB T1 parameter), use the lapb t1 interface configuration command.
lapb t1 milliseconds
milliseconds | Time in milliseconds. It can be a value from 1 through 64000. The default is 3000 milliseconds. |
3000 milliseconds
Interface configuration
The retransmission timer determines how long a transmitted frame can remain unacknowledged before the LAPB software polls for an acknowledgment. The design of the LAPB protocol specifies that a frame is presumed to be lost if it is not acknowledged within T1; a T1 value that is too small may result in duplicated control information, which can severely disrupt service.
To determine an optimal value for the retransmission timer, use the privileged EXEC command ping to measure the round-trip time of a maximum-sized frame on the link. Multiply this time by a safety factor that takes into account the speed of the link, the link quality, and the distance. A typical safety factor is 1.5. Choosing a larger safety factor can result in slower data transfer if the line is noisy. However, this disadvantage is minor compared to the excessive retransmissions and effective bandwidth reduction caused by a timer setting that is too small.
The following example sets the T1 retransmission timer to 2,000 milliseconds:
interface serial 0
lapb t1 2000
To set the T4 idle timer, after which the router sends out a Poll packet to determine whether the link has suffered an unsignaled failure, use the lapb t4 interface configuration command.
lapb t4 seconds
seconds | Number of seconds between reception of the last frame and the transmission of the outgoing Poll. The default value is 0 seconds, which disables the T4 timer feature. |
0 seconds, which disables the T4 timer feature.
Interface configuration
Any nonzero T4 duration must be greater than T1, the LAPB retransmission timer period.
The following example will poll the other end of an active link if it has been 10 seconds since the last frame was received; if the far host has failed, the service will be declared down after N2 tries are timed out.
interface serial0 encapsulation x25 lapb t4 10
To display X.25 Level 3 parameters for LAN interfaces (such as Ethernet or Token Ring) and other information pertaining to CMNS traffic activity, use the show cmns EXEC command.
show cmns [type number]
type | (Optional) Interface type. |
number | (Optional) Interface number. |
EXEC
The following is sample output from the show cmns command for an Ethernet interface:
Router# show cmns Ethernet1 is administratively down, line protocol is down Hardware address is 0000.0c02.5f4c, (bia 0000.0c2.5f4c), state R1
Modulo 8, idle 0, timer 0, nvc 1 Window size: input 2, output 2, Packet size: input 128, output 128 Timer: TH 0 Channels: Incoming-only none, Two-way 1-4095, Outgoing-only none RESTARTs 0/0 CALLs 0+0/0+0/0+0 DIAGs 0/0
Table 12-1 describes significant fields shown in the display.
| Field | Description |
|---|---|
Ethernet1 is down | Interface is currently active and inserted into network (up) or inactive and not inserted (down), or disabled (administratively down). |
line protocol is {up | down} | Indicates whether the software processes that handle the line protocol believes the interface is usable. |
Hardware address | MAC address for this interface. |
bia | |
state R1 | State of the interface. R1 is normal ready state (this should always be R1). |
modulo 8 | Modulo value; determines the packet sequence numbering scheme used. |
idle 0 | Number of minutes the router waits before closing idle virtual circuits. |
timer 0 | Value of the interface time; should always be zero. |
nvc 1 | Maximum number of simultaneous virtual circuits permitted to and from a single host for a particular protocol. |
Window size: | Default window sizes (in packets) for the interface. (CMNS cannot originate or terminate calls.) |
input 2 | Default input window size is two packets. |
output 2 | Default output window size is two packets. |
Packet size: | Default packet sizes for the interface. (CMNS cannot originate or terminate calls). |
input 128 | Default input maximum packet size is 128 bytes. |
output 128 | Default output maximum packet size is 128 bytes. |
TH 0 | X.25 delayed acknowledgment threshold. Should always be zero. |
Channels: Incoming-only: none, Two-way: 1-4095, | Virtual circuit ranges for this interface per LLC2 connection. |
RESTARTs 0/0 | Restarts sent/received. |
CALLs 0+0/0+0/0+0 | Successful calls + failed calls/calls sent + calls failed/calls received + calls failed. |
DIAGs 0/0 | Diagnostic messages sent+received. |
To display information about a serial interface, use the show interfaces serial EXEC command.
show interfaces serial number
number | Interface port number. |
EXEC
The following is a partial sample output from the show interfaces serial command for a serial interface using LAPB encapsulation:
Router# show interfaces serial 1 LAPB state is SABMSENT, T1 3000, N1 12056, N2 20, k7,Protocol ip
VS 0, VR 0, RCNT 0, Remote VR 0, Retransmissions 2 IFRAMEs 0/0 RNRs 0/0 REJs 0/0 SABMs 3/0 FRMRs 0/0 DISCs 0/0
Table 12-2 shows the fields relevant to all LAPB connections.
| Parameter | Description |
|---|---|
LAPB state is | State of the LAPB protocol. |
T1 3000, N1 12056, ... | Current parameter settings. |
Protocol | Protocol encapsulated on a LAPB link; this field is not present on interfaces configured for multiprotocol LAPB or X.25 encapsulations. |
VS | Modulo 8 frame number of the next outgoing I-frame. |
VR | Modulo 8 frame number of the next I-frame expected to be received. |
RCNT | Number of received I-frames that have not yet been acknowledged. |
Remote VR | Number of the next I-frame the remote expects to receive. |
Retransmissions | Count of current retransmissions due to expiration of T1. |
Window is closed | No more frames can be transmitted until some outstanding frames have been acknowledged. This message should be displayed only temporarily. |
IFRAMEs | Count of Information frames in the form of sent/received. |
RNRs | Count of Receiver Not Ready frames in the form of sent/received. |
REJs | Count of Reject frames in the form of sent/received. |
SABMs | Count of Set Asynchronous Balanced Mode commands in the form of sent/received. |
FRMRs | Count of Frame Reject frames in the form of sent/received. |
DISCs | Count of Disconnect commands in the form of sent/received. |
The following is a partial sample output from the show interfaces command for a serial X.25 interface:
Router# show interfaces serial 1 X25 address 000000010100, state R1, modulo 8, idle 0, timer 0, nvc 1 Window size: input 2, output 2, Packet size: input 128, output 128 Timers: T20 180, T21 200, T22 180, T23 180, TH 0 Channels: Incoming-only none, Two-way 1-1024, Outgoing-only none (configuration on RESTART: modulo 8, Window size: input 2 output 2, Packet size: input 128, output 128 Channels: Incoming-only none, Two-way 5-1024, Outgoing-only none) RESTARTs 3/2 CALLs 1000+2/1294+190/0+0/ DIAGs 0/0
The stability of the X.25 protocol requires that some parameters not be changed without a RESTART of the protocol. Any change to these parameters will be held until a RESTART is sent or received. If any of these parameters will change, the configuration on RESTART information will be output as well as the values that are currently in effect.
Table 12-3 describes significant fields shown in the display.
| Field | Description |
|---|---|
X25 address 000000010100 | Address used to originate and accept calls. |
state R1 | State of the interface. Possible values are:
If the state is R2 or R3, the interface is awaiting acknowledgment of a Restart packet. |
modulo 8 | Modulo value; determines the packet sequence numbering scheme used. |
idle 0 | Number of minutes the router waits before closing idle virtual circuits that it originated or accepted. |
timer 0 | Value of the interface timer, which is zero unless the interface state is R2 or R3. |
nvc 1 | Default maximum number of simultaneous virtual circuits permitted to and from a single host for a particular protocol. |
Window size: input 2, output 2 | Default window sizes (in packets) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router. |
Packet size: input 128, output 128 | Default maximum packet sizes (in bytes) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router. |
Timers: T20 180, T21 200, T22 180, T23 180 | Values of the X.25 timers:
|
TH0 | Packet acknowledgment threshold (in packets). This value determines how many packets are received before sending an explicit acknowledgment; the default value (0) sends an explicit acknowledgment only when the incoming window is full. |
Channels: Incoming-only none | Displays the virtual circuit ranges for this interface. |
RESTARTs 3/2 | Shows RESTART packet statistics for the interface using the format Sent/Received. |
CALLs 1000+2/1294+190/0+0 | Successful calls sent + failed calls/calls received + calls failed/calls forwarded + calls failed. Calls forwarded are counted as calls sent. |
DIAGs 0/0 | Diagnostic messages sent+received. |
To display active LLC2 connections, use the show llc2 EXEC command.
show llc2cThis command has no arguments or keywords.
EXEC
The following is sample output from the show llc2 command:
Router# show llc2 TokenRing0 DTE=1000.5A59.04F9,400022224444 SAP=04/04, State=NORMAL V(S)=5, V(R)=5, Last N(R)=5, Local Window=7, Remote Window=127 ack-max=3, n2=8, Next timer in 7768 xid-retry timer 0/60000 ack timer 0/1000 p timer 0/1000 idle timer 7768/10000 rej timer 0/3200 busy timer 0/9600 ack-delay timer 0/3200 CMNS Connections to:
Address 1000.5A59.04F9 via Ethernet2
Protocol is up
Interface type X25-DCE RESTARTS 0/1
Timers: T10 1 T11 1 T12 1 T13 1
The display includes a CMNS addendum, indicating that LLC2 is running with CMNS. When LLC2 is not running with CMNS, the show llc2 command does not display a CMNS addendum.
Table 12-4 describes significant fields shown in the display.
| Field | Description |
|---|---|
TokenRing0 | Name of interface on which the session is established. |
DTE=1000.5A59.04F9, 400022224444 | Address of the station to which the router is talking on this session. (The router's address is the MAC address of the interface on which the connection is established, except when Local Acknowledgment or SDLLC is used, in which case the address used by the router is shown as in this example, following the DTE address and separated by a comma.) |
SAP=04/04 | Other station's and router's (remote/local) Service Access Point for this connection. The SAP is analogous to a "port number" on the router and allows for multiple sessions between the same two stations. |
State= ADM SETUP RESET D_CONN ERROR AWAIT AWAIT_REJ | Current state of the LLC2 session which are any of the following: Asynchronous Disconnect Mode—A connection is not established, and either end can begin one. Request to begin a connection has been sent to the remote station, and this station is waiting for a response to that request. A previously open connection has been reset because of some error by this station, and this station is waiting for a response to that reset command. This station has requested a normal, expected, end of communications with the remote, and is waiting for a response to that disconnect request. This station has detected an error in communications and has told the other station about it. This station is waiting for a reply to its posting of this error. Connection between the two sides is fully established, and normal communication is occurring. Normal communication state exists, except busy conditions on this station make it such that this station cannot receive information frames from the other station at this time. Out-of-sequence frame has been detected on this station, and this station has requested that the other resend this information Normal communication exists, but this station has had a timer expire, and is trying to recover from it (usually by resending the frame that started the timer). A combination of the AWAIT and BUSY states. A combination of the AWAIT and REJECT states. |
V(S)=5 | Sequence number of the next information frame this station will send. |
V(R)=5 | Sequence number of the next information frame this station expects to receive from the other station. |
Last N (R)=5 | Last sequence number of this station's transmitted frames acknowledged by the remote station. |
Local Window=7 | Number of frames this station may send before requiring an acknowledgment from the remote station. |
Remote Window=127 | Number of frames this station can accept from the remote. |
ack-max=3, n2=8 | Value of these parameters, as given in the previous configuration section. |
Next timer in 7768 | Number of milliseconds before the next timer, for any reason, goes off. |
xid-retry timer 0/60000 .... | A series of timer values in the form of next-time/time-between, where "next-time" is the next time, in milliseconds, that the timer will wake, and "time-between" is the time, in milliseconds, between each timer wakeup. A "next-time" of zero indicates that the given timer is not enabled, and will never wake. |
CMNS Connections to: Protocol is up Interface type X25-DCE RESTARTS 0/1 Timers: | CMNS addendum when LLC2 is running with the CMNS protocol contains the following: MAC address of remote station. Up indicates the LLC2 and X.25 protocols are in a state where incoming and outgoing Call Requests can be made on this LLC2 connection. One of the following: X25-DCE, X25-DTE, or X25-DXE (either DTE or DCE). Restarts sent/received on this LLC2 connection. T10, T11, T12, T13 (or T20, T21, T22, T23 for DTE); these are Request packet timers. These are similar in function to X.25 parameters of the same name. |
To display information about configured address maps, use the show x25 map EXEC command.
show x25 mapThis command has no arguments or keywords.
EXEC
The show x25 map command shows information about the following:
The following is sample output from the show x25 map command:
Router# show x25 map
Serial0: X.121 1311001 <--> ip 131.108.170.1
PERMANENT, BROADCAST, 2 VCS: 3 4*
Serial0: X.121 1311005 <--> appletalk 128.1
PERMANENT
Serial1: X.121 1311005 <--> bridge
PERMANENT, BROADCAST
Serial2: X.121 001003 <--> apollo 1.3,
appletalk 1.3,
ip 131.108.1.3,
decnet 1.3,
novell 1.0000.0c04.35df,
vines 00000001:0003,
xns 1.0000.0c04.35df,
clns
PERMANENT, NVC 8, 1 VC: 1024
Table 12-5 describes fields shown in the display.
| Field | Description |
|---|---|
Serial0 | Interface on which this map is configured. |
X.121 1311001 | X.121 address of the mapped encapsulation host. |
ip 131.108.170.1 | Type and address of the higher-level protocol(s) mapped to the remote host. Bridge maps do not have a higher-level address; all bridge datagrams are sent to the mapped X.121 address. CLNS maps refer to a configured neighbor as identified by the X.121 address. |
PERMANENT | Address-mapping type that has been configured for the interface in this entry. Possible values include the following:
|
BROADCAST | If any options are configured for an address mapping, they will be listed; the example shows a maps that is configured to forward datagram broadcasts to the mapped host. |
2 VCs: | If the map has any active virtual circuits, they are identified. |
3 4* | Identifies the circuit number of the active virtual circuits. The asterisk (*) marks the virtual circuit last used to send data. Note that a single protocol virtual circuit can be associated with a multiprotocol map. |
To display the one-to-one mapping of the host IP addresses and the remote BFE device's IP addresses, use the show x25 remote-red EXEC command.
show x25 remote-redThis command has no arguments or keywords.
EXEC
The following is sample output from the show x25 remote-red command:
Router# show x25 remote-redEntry REMOTE-RED REMOTE-BLACK INTERFACE1 21.0.0.3 21.0.0.7 serial32 21.0.0.10 21.0.0.6 serial13 21.0.0.24 21.0.0.8 serial3
Table 12-6 describes significant fields shown in the display.
| Field | Description |
|---|---|
Entry | Address mapping entry. |
REMOTE-RED | Host IP address. |
REMOTE-BLACK | IP address of the remote BFE device. |
INTERFACE | Name of interface through which communication with the remote BFE device will take place. |
To display the X.25 routing table, use the show x25 route EXEC command.
show x25 routeThis command has no arguments or keywords.
EXEC
The following is sample output from the show x25 route command:
Router# show x25 route Number X.121 CUD Forward To 1 1311001 Serial0, 0 uses 2 1311002 131.108.170.10, 0 uses 3 1311003 00 alias Serial0, 2 uses
Table 12-7 describes significant fields shown in the display.
| Field | Description |
|---|---|
Number | Number identifying the entry in the X.25 routing table. |
X.121 address | X.121 address pattern associated with this entry. |
CUD | Call User Data, if any, that has been configured for this route. |
Forward To | Router interface or IP address to which the router will forward a CALL destined for the X.121 address pattern in this entry. This field also includes the number of uses of this route. |
To display information about active switched virtual circuits (SVCs) and permanent virtual circuits (PVCs), use the show x25 vc EXEC command.
show x25 vc [lcn]
lcn | (Optional) Logical channel number (LCN). |
EXEC
To examine a particular virtual circuit, add an LCN argument to the show x25 vc command.
This command displays information about virtual circuits that are used for any of the following:
The connectivity information displayed will vary according to the traffic carried by the virtual circuit. For multiprotocol circuits, the output varies depending on the number and identity of the protocols mapped to the X.121 address and the encapsulation method selected for the circuit.
This section provides three sample displays and tables that describe the fields in each display.
The following sample display shows a virtual circuit that is being used to encapsulate traffic between the router and a remote host:
Router# show x25 vc 1024
SVC 1024, State: D1, Interface: Serial0
Started 0:00:31, last input 0:00:31, output 0:00:31
Connects 170090 <-->
compressedtcp 131.108.170.90
ip 131.108.170.90
multiprotocol CUD PID, standard Tx data PID, Reverse charged
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE
Window is closed
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 12-8 describes the general fields shown in the output; Table 12-9 describes the fields specific to encapsulation virtual circuits shown in the output.
| Field | Description |
|---|---|
SVC 1024 | Identifies the type (switched or permanent) and the number of the virtual circuit. |
State | State of the virtual circuit (which is independent of the states of other virtual circuits); D1 is the normal ready state. (See the International Telecommunication Union Telecommunication Standardization Sector (ITU-T)1 X.25 Recommendation for a description of virtual circuit states.) |
Interface | Interface or subinterface on which the virtual circuit is established. |
Started | Time elapsed since the virtual circuit was created. |
last input | Time of last input. |
output | Shows time of last output. |
Connects...<-->... | Describes the traffic-specific connection information. See Table 12-9, Table 12-10, and Table 12-11 for more information. |
Window size | Window sizes for the virtual circuit. |
Packet size | Maximum packet sizes for the virtual circuit. |
PS | Current send sequence number. |
PR | Current receive sequence number. |
ACK | Last acknowledged incoming packet. |
Remote PR | Last PR number received from the other end of the circuit. |
RCNT | Count of unacknowledged input packets. |
RNR | State of the Receiver Not Ready flag; this field is true if the network sends a receiver-not-ready packet. |
Window is closed | This line appears if the router cannot transmit any more packets until the X.25 layer 3 peer has acknowledged some outstanding packets. |
Retransmits | Number of times a supervisory packet (RESET or CLEAR) has been retransmitted. |
Timer | A nonzero time value indicates that a control packet has not been acknowledged yet or that the virtual circuit is being timed for inactivity. |
Reassembly | Number of bytes received and held for reassembly (packets with the More bit set are reassembled into datagrams for encapsulation virtual circuits; switched X.25 traffic is not reassembled). |
Held Fragments/Packets | Number of X.25 data fragments to transmit to complete an outgoing datagram, and the number of datagram packets waiting for transmission. |
Bytes | Total number of bytes sent and received. The Packets, Resets, RNRs, REJs, and INTs fields show the total sent and received packet counts of the indicated types. (RNR is Receiver Not Ready, REJ is Reject, and INT is Interrupt). |
| 1The ITU-T carries out the functions of the former Consultative Committee for International Telegraph and Telephone (CCITT). |
Table 12-9 describes the connection description fields for virtual circuits carrying encapsulation traffic.
| Field | Description |
|---|---|
170090 | The X.121 address of the remote host. |
ip 131.108.170.90 | The higher-level protocol and address values that are mapped to the virtual circuit. |
multiprotocol CUD PID | Identifies the method used for the protocol identification (PID) in the Call User Data (CUD) field. Since PVCs are not set up using a Call packet, this field is not displayed for encapsulation PVCs. The available methods are as follows:
|
standard Tx data PID | Identifies the method used for protocol identification (PID) when sending datagrams. The available methods are as follows:
|
Reverse charged | Some important virtual circuit information might be displayed as needed; a DDN IP precedence encapsulation value, reverse charged virtual circuits, and virtual circuits that allow the D-bit procedure. |
The following sample display shows virtual circuits carrying locally switched X.25 traffic:
Router# show x25 vc PVC 1, State: D1, Interface: Serial2 Started 0:01:26, last input never, output never PVC <--> Serial1 PVC 1 connected Window size input: 2, output: 2 Packet size input: 128, output: 128 PS: 0 PR: 0 ACK: 0 Remote PR: 0 RCNT: 0 RNR: FALSE Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0 Held Fragments/Packets: 0/0 Bytes 0/0 Packets 0/0 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0 SVC 5, State: D1, Interface: Serial2 Started 0:00:16, last input 0:00:15, output 0:00:15 Connects 170093 <--> 170090 from Serial1 VC 5 Window size input: 2, output: 2 Packet size input: 128, output: 128 PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0 Held Fragments/Packets: 0/0 Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 12-10 lists the connection description fields for virtual circuits carrying locally switched X.25 traffic.
| Field | Description |
|---|---|
PVC | Flags PVC information. |
Serial1 PVC 1 | Identifies the other half of a local PVC connection. |
connected | Identifies the state of the PVC. If the PVC is not connected, the status of the PVC will also be displayed. See Table 12-12 for PVC status messages. |
170093 | Identifies the Calling (source) Address of the connection. If a Calling Address Extension was encoded in the call facilities, it will also be displayed. If the source host is a CMNS host, its MAC address will also be displayed. |
170090 | Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it will also be displayed. If the destination host is a CMNS host, its MAC address will also be displayed. |
from Serial1 VC 5 | Indicates the direction of the call ("from" or "to") and the connecting interface and virtual circuit number. |
The following sample display shows virtual circuits carrying remotely switched X.25 traffic.
Router# show x25 vc PVC 2, State: D1, Interface: Serial2 Started 0:01:25, last input never, output never PVC <--> [131.108.165.92] Serial2/0 PVC 1 connected XOT between 131.108.165.91, 1998 and 131.108.165.92, 27801 Window size input: 2, output: 2 Packet size input: 128, output: 128 PS: 0 PR: 0 ACK: 0 Remote PR: 0 RCNT: 0 RNR: FALSE Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0 Held Fragments/Packets: 0/0 Bytes 0/0 Packets 0/0 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0 SVC 6, State: D1, Interface: Serial2 Started 0:00:04, last input 0:00:04, output 0:00:04 Connects 170093 <--> 170090 from XOT between 131.108.165.91, 1998 and 131.108.165.92, 27896 Window size input: 2, output: 2 Packet size input: 128, output: 128 PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0 Held Fragments/Packets: 0/0 Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 12-11 lists the connection description fields for virtual circuits carrying remotely switched X.25 traffic.
| Field | Description |
|---|---|
PVC | Flags PVC information. |
[131.108.165.92] | Indicates the IP address of the router remotely connecting the PVC. |
Serial 2/0 PVC 1 | Identifies the remote interface and PVC number. |
connected | Identifies the state of the PVC. If the PVC is not connected, the status of the PVC will also be displayed. See Table 12-12 for the PVC status messages. |
170093 | Identifies the Calling (source) Address of the connection. If a Calling Address Extension was encoded in the call facilities, it will also be displayed. |
170090 | Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it will also be displayed. |
from | Indicates the direction of the call ("from" or "to"). |
XOT between... | Identifies the IP addresses and port numbers of the XOT connection. |
Table 12-12 lists the PVC states that can be reported. These states are also reported by the debug x25 command in PVC-SETUP packets (for remote PVCs only) as well as in the PVCBAD system error message. Some states apply only to remotely switched PVCs.
| Field | Description |
|---|---|
waiting to connect | The PVC is waiting to be processed for connecting. |
dest. disconnected | The other end disconnected the PVC. |
PVC/TCP connection refused | A remote PVC XOT TCP connection was tried and refused. |
PVC/TCP routing error | A remote PVC XOT TCP connection routing error was reported. |
PVC/TCP connect timed out | A remote PVC SOT TCP connection attempt timed out. |
trying to connect via TCP | A remote PVC XOT TCP connection is established and is in the process of connecting. |
awaiting PVC-SETUP reply | A remote PVC has initiated an XOT TCP connection and is waiting fro a reply to the setup message. |
connected | The PVC is up. |
no such dest. interface | The remote destination interface was reported to be in error by the remote router. |
dest interface is not up | The target interface's X.25 service is down. |
non-X.25 dest. interface | The target interface isn't configured for X.25. |
no such dest. PVC | The targeted PVC does not exist. |
dest PVC config mismatch | The targeted PVC is already connected. |
mismatched flow control values | The configured flow control values do not match. |
can't support flow control values | The window sizes or packet sizes of the PVC cannot be supported by one of its two interfaces. |
To configure the router to accept all reverse charge calls, use the x25 accept-reverse interface configuration command. To disable this facility, use the no form of this command.
x25 accept-reverseThis command has no arguments or keywords.
Disabled
Interface configuration
This command causes the interface to accept reverse charge calls by default. This behavior also can be configured on a per-peer basis using the x25 map interface configuration command.
The following example sets acceptance of reverse charge calls:
interface serial 0
x25 accept-reverse
x.121-address | Variable-length X.121 address. The address is assigned by the X.25 network service provider. |
DDN and BFE encapsulations have a default interface address generated from the interface IP address; for proper DDN or BFE operation, this generated X.121 address should not be changed. Standard X.25 encapsulations do not have a default.
Interface configuration
When connecting to a PDN, the PDN administration will assign the X.121 address that should be used. Other applications (for example, a private X.25 service), may assign arbitrary X.121 addresses as required by the network and service design. X.25 interfaces that only engage in X.25 switching do not need to assign an X.121 address.
The following example sets the X.121 address for the interface:
interface serial 0 encapsulation x25
x25 address 00000123005
The address must match that assigned by the X.25 network service provider.
To specify how a router configured for x25 bfe-emergency decision will participate in emergency mode, use the x25 bfe-decision interface configuration command.
x25 bfe-decision {no | yes | ask}
no | Prevents the router from participating in emergency mode and from sending address translation information to the BFE device. |
yes | Allows the router to participate in emergency mode and to send address translation information to the BFE when the BFE enters emergency mode. The router obtains this information from the table created by the x25 remote-red command. |
ask | Configures the router to prompt the console operator to enter the bfe EXEC command. |
The router does not participate in emergency mode.
Interface configuration
The following example configures interface Serial 0 to require an EXEC command from the administrator before it participates in emergency mode. The host IP address is 21.0.0.12, and the address of the remote BFE unit is 21.0.0.1. When the BFE enters emergency mode, the router will prompt the administrator for EXEC command bfe enter to direct the router to participate in emergency mode.
interface serial 0 x25 bfe-emergency decision x25 remote-red 21.0.0.12 remote-black 21.0.0.1 x25 bfe-decision ask
bfe
x25 bfe-emergency
x25 remote-red
To configure the circumstances under which the router participates in emergency mode, use the x25 bfe-emergency interface configuration command.
x25 bfe-emergency {never | always | decision}
never | Prevents the router from sending address translation information to the BFE. If it does not receive address translation information, the BFE cannot open a new connection for which it does not know the address. |
always | Allows the router to pass address translations to the BFE when it enters emergency mode and an address translation table has been created. |
decision | Directs the router to wait until it receives a diagnostic packet from the BFE device indicating that the emergency mode window is open. The window is only open when a condition exists that allows the BFE is to enter emergency mode. When the diagnostic packet is received, the router's participation in emergency mode depends on how it is configured using the x25 bfe-decision command. |
The router does not send address translation information to the BFE.
Interface configuration
The following example configures interface Serial 0 to require an EXEC command from the administrator before it participates in emergency mode. The host IP address is 21.0.0.12, and the address of the remote BFE unit is 21.0.0.1. When the BFE enters emergency mode, the router will prompt the administrator for EXEC command bfe enter to direct the router to participate in emergency mode.
interface serial 0 x25 bfe-emergency decision x25 remote-red 21.0.0.12 remote-black 21.0.0.1 x25 bfe-decision ask
protocol | Specifies the protocol to assume; may be ip or pad. |
No default protocol is set.
Interface configuration
This command specifies the protocol assumed by the router for incoming calls with unknown or missing Call User Data. If you do not use the x25 default interface configuration command, the router clears any incoming calls with unrecognized Call User Data.
The following example establishes IP as the default protocol for X.25 calls:
interface serial 0 x25 default ip
To force facilities on a per-call basis for calls originated by the router (switched calls are not affected), use the x25 facility interface configuration command. To disable a facility, use the no form of this command.
x25 facility facility-keyword value
facility-keyword | User facility. |
value | Facility value; see Table 12-13 for a list of supported facilities and their values. |
No facility is sent.
Interface configuration
Table 12-13 lists X.25 user facilities.
| User Facility | Description |
|---|---|
cug number | |
packetsize in-size out-size | Proposes input maximum packet size (in-size) and output maximum packet size (out-size) for flow control parameter negotiation. Both values must be one of the following values: 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096. |
windowsize in-size out-size | Proposes the packet count for input windows (in-size) and output windows (out-size) for flow control parameter negotiation. Both values must be in the range 1 to 127 and must not be greater than or equal to the value set for the x25 modulo command. |
reverse | Specifies reverses charging on all calls originated by the interface. |
throughput in out | |
transit-delay value | Specifies a network transit delay for the duration of outgoing calls for networks that support transit delay. The transit delay value can be between 0 and 65534 milliseconds. |
rpoa name | Specifies the name defined by the x25 rpoa command for a list of transit Recognized Private Operation Agencies (RPOAs) to use in outgoing Call Request packets. |
The following example specifies a transit delay value in an X.25 configuration:
interface serial 0
x25 facility transit-delay 24000
The following example sets an RPOA name and then send the list via the X.25 user facilities:
x25 rpoa green_list 23 35 36
interface serial 0
x25 facility rpoa green_list
To set the highest incoming-only virtual circuit number, use the x25 hic interface configuration command.
x25 hic circuit-number
circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no incoming-only virtual circuit range. The default is 0. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an incoming only virtual circuit range. Incoming is from the perspective of the X.25 DTE. If you do not want any outgoing calls from your DTE, configure both ends to disable the two-way range (set ltc and htc to 0) and configure an incoming-only range. Any incoming-only range must come before (that is, must be numerically less than) any two-way range. Any two-way range must come before any outgoing-only range.
The following example sets a valid incoming-only virtual circuit range of 1 to 5:
interface serial 0
x25 lic 1 x25 hic 5 x25 ltc 6
To set the highest outgoing-only virtual circuit number, use the x25 hoc interface configuration command.
x25 hoc circuit-number
circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no outgoing-only virtual circuit range. The default is 0. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an outgoing only virtual circuit range. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls on your DTE, disable the two-way range (set ltc and htc to 0) and configure an outgoing-only range. Any outgoing-only range must come after (that is, be numerically greater than) any other range.
The following example sets a valid outgoing-only virtual circuit range of 2000 to 2005:
interface serial 0
x25 loc 2000 x25 hoc 2005
To set the maximum number of packets to hold until a virtual circuit is able to transmit, use the x25 hold-queue interface configuration command. To remove this command from the configuration file and restore the default value, use the no form of this command without an argument.
x25 hold-queue packets
packets | Number of packets. A hold queue value of 0 allows an unlimited number of packets in the hold queue. This argument is optional for the no form of this command. The default is 10 packets. |
10 packets
Interface configuration
If you set the queue-size to 0 when using the no x25 hold-queue command, there will be no hold queue limit. While this will prevent drops until the router runs out of memory, it is only rarely appropriate. A virtual circuit hold queue value is determined when it is created; changing this parameter will not affect the hold queue limits of the existing virtual circuits.
The following example sets the X.25 hold queue to hold 25 packets:
interface serial 0
x25 hold-queue 25
A dagger (†) indicates that the command is documented in another chapter.
To start the hold-vc-timer to prevent additional calls to a destination for a given period of time (thus preventing overruns on some X.25 switches caused by Call Request packets), use the x25 hold-vc-timer interface configuration command. To restore the default value for the timer, use the no form of this command
x25 hold-vc-timer minutes
minutes | Number of minutes to prevent calls from going to a previously failed destination. Incoming calls will still be accepted. The default is 0 minutes. |
0 minutes
Interface configuration
Only Call Requests that the router originates will be held down; routed X.25 Call Requests are not affected by this parameter.
Upon receiving a Clear Request for an outstanding Call Request, the X.25 support code immediately tries another Call Request if it has more traffic to send, and this action might cause overrun problems.
The failed VC(s) may be observed with the show x25 vc command; they are renumbered to the illegal value 4096 and have the nonstandard state X1.
The following example sets the hold-vc-timer to 3 minutes:
interface serial 0
x25 hold-vc-timer 3
To set the highest two-way virtual circuit number, use the x25 htc interface configuration command.
x25 htc circuit-number
circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no two-way virtual circuit range. The default is 1024 for X.25 network service interfaces; 4095 for CMNS network service interfaces. |
1024 for X.25 network service interfaces; 4095 for CMNS network service interfaces.
Interface configuration
This command is applicable if the X.25 switch is configured for a two-way virtual circuit range. Any two-way virtual circuit range must come after (that is, be numerically larger than) any incoming-only range, and must come before any outgoing-only range.
The following example sets a valid two-way virtual circuit range of 5 to 25:
interface serial 0 x25 ltc 5 x25 htc 25
To define the period of inactivity after which the router can clear a switched virtual circuit (SVC), use the x25 idle interface configuration command.
x25 idle minutes
minutes | Idle period in minutes. The default is 0, which causes the router to keep the SVC open indefinitely. |
0 (causes the router to keep the SVC open indefinitely)
Interface configuration
Calls originated and terminated by the router are cleared; PAD and switched virtual circuits are not affected. To clear one or all virtual circuits at once, use the privileged EXEC command clear x25-vc.
The following example sets a 5-minute wait period before an idle circuit is cleared:
interface serial 2
x25 idle 5
To enable the router to use the IP precedence value when it opens a new virtual circuit, use the x25 ip-precedence interface configuration command. To cause the precedence value to be ignored when opening virtual circuits, use the no form of this command.
x25 ip-precedenceThis command has no arguments or keywords.
The routers open one virtual circuit for all types of service.
Interface configuration
This feature is only useful for DDN or BFE encapsulations, because only these methods have an IP precedence facility defined to allow the source and destination devices to both use the VC for traffic of the given IP priority.
There is a problem associated with this feature in that some hosts send nonstandard data in the IP TOS field, thus causing multiple wasteful virtual circuits to be created.
Four virtual circuits may be opened based on IP precedence to encapsulate routine, priority, immediate, and all higher precedences.
The nvc limit specified for the map or the interface default nvc limit still applies.
The following example allows new IP encapsulation virtual circuits based on the IP precedence:
interface serial 3
x25 ip-precedence
To set the interface default maximum input packet size to match that of the network, use the x25 ips interface configuration command.
x25 ips bytes
bytes | Byte count. It can be one of the following values: 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096. The default is 128 bytes. |
128 bytes
Interface configuration
X.25 network connections have a default maximum input packet size set by the network administrator. Larger packet sizes require less overhead processing. To send a packet larger than the X.25 packet size over an X.25 virtual circuit, a router must break the packet into two or more X.25 packets with the M-bit ("more data" bit) set. The receiving device collects all packets with the M-bit set and reassembles the original packet.
The following example sets the default maximum packet sizes to 512:
interface serial 1
x25 ips 512 x25 ops 512
To set the lowest incoming-only virtual circuit number, use the x25 lic interface configuration command.
x25 lic circuit-number
circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no incoming-only virtual circuit range. The default is 0. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an incoming only virtual circuit range. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls on your DTE, disable the two-way range (set ltc and htc to 0) and configure an outgoing-only range. Any outgoing-only range must come after (that is, be numerically greater than) any other range.
This command is applicable if you have the X.25 switch configured for two way virtual circuit range.
The following example sets a valid incoming-only virtual circuit range of 1 to 5 and sets the lowest two-way virtual circuit number:
interface serial 0
x25 lic 1 x25 hic 5 x25 ltc 6
This command has no arguments or keywords.
Forcing packet-level restarts is the default and is necessary for networks that expect this behavior.
Interface configuration
The following example disables the link level restart:
interface serial 3
no x25 linkrestart
circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no outgoing-only virtual circuit range. The default is 0. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an outgoing only virtual circuit range. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls from your DTE, configure the loc and hoc values and set the ltc and htc values to 0.
The following example sets a valid outgoing-only virtual circuit range of 2000 to 2005:
interface serial 0
x25 loc 2000 x25 hoc 2005
To set the lowest two-way virtual circuit number, use the x25 ltc interface configuration command.
x25 ltc circuit-number
circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no two-way virtual circuit range. The default is 1. |
1
Interface configuration
This command is applicable if you have the X.25 switch configured for a two-way virtual circuit range. Any two-way virtual circuit range must come after (that is, be numerically larger than) any incoming-only range, and must come before any outgoing-only range.
The following example sets a valid two-way virtual circuit range of 5 to 25:
interface serial 0 x25 ltc 5 x25 htc 25
To set up the LAN protocols-to-remote host mapping, use the x25 map interface configuration command. To retract a prior mapping, use the no form of this command with the appropriate network protocol(s) and X.121 address argument.
x25 map protocol address [protocol2 address2[...[protocol9 address9]]] x.121-address [option]
protocol | Protocol type, entered by keyword. Supported protocols are entered by keyword, as listed in Table 12-14. As many as nine protocol and address pairs can be specified in one command line. |
address | Protocol address. |
x.121-address | X.121 address of the remote host. |
option | (Optional) Provides additional functionality or allows X.25 facilities to be specified for originated calls. Can be any of the options listed in Table 12-15. |
No LAN protocol-to-remote host mapping is set up.
Interface configuration
Because no defined protocol can dynamically determine LAN protocol-to-remote host mappings, you must enter all of the information for each host with which the router may exchange X.25 encapsulation traffic.
Two methods are available to encapsulate traffic, Cisco's long-available encapsulation method and the IETF's standard method (defined in RFC 1356); the latter allows hosts to exchange several protocols over a single virtual circuit. Cisco's encapsulation method is the default (for backward compatibility, unless the interface configuration command specifies ietf.
When you configure multiprotocol maps, you can specify a maximum of nine protocol and address pairs in an x25 map command. However, you can specify a protocol once only. For example, you can specify the IP protocol and an IP address, but you cannot specify another IP address. If compressedtcp and ip are both specified, the same IP address must be used.
Bridging is supported only using Cisco's traditional encapsulation method. For correct operation, bridging maps must specify the broadcast option.
Since most datagram routing protocols rely on broadcasts or multicasts to send routing information to their neighbors, the broadcast keyword is needed to run such routing protocols over X.25.
Encapsulation maps might also specify that traffic between the two hosts should be compressed, thus increasing the effective bandwidth between them at the expense of memory and computation time. Each compression virtual circuit requires memory and computation resources, so compression should be used with care and monitored to maintain acceptable resource usage and overall router performance.
OSPF treats a nonbroadcast, multiaccess network such as X.25 much the same way it treats a broadcast network in that it requires selection of a designated router. In previous releases, this required manual assignment in the OSPF configuration using the neighbor interface router configuration command. When the x25 map command is included in the configuration with the broadcast, and the ip ospf network command (with the broadcast keyword) is configured, there is no need to configure any neighbors manually. OSPF will now run over the X.25 network as a broadcast network. (Refer to the ip ospf network interface command for more detail.)
You can modify the options of an x25 map command by restating the complete set of protocols and addresses specified for the map, followed by the desired options. To delete a map command, you must also specify the complete set of protocols and addresses; the options can be omitted when deleting a map.
Once defined, a map's protocols and addresses cannot be changed; this is because the router cannot determine whether you want to add to, delete from, or modify an existing map's protocol and address specification (or simply mistyped the command). To change a map's protocol and address specification, you must delete it and create a new map.
A given protocol/address pair cannot be used in more than one map on the same interface.
Table 12-14 lists the protocols supported by X.25.
| Keyword | Protocol |
|---|---|
apollo | Apollo Domain |
appletalk | AppleTalk |
bridge | Bridging1 |
clns | ISO Connectionless Network Service |
cmns | ISO Connection-Mode Network Service2 |
compressedtcp | TCP header compression |
decnet | DECnet |
ip | IP |
ipx | Novell IPX |
pad | PAD links3 |
qllc | SNA encapsulation in X.254 |
vines | Banyan VINES |
xns | XNS |
Table 12-15 lists the map options supported by X.25.
| Option | Description |
|---|---|
compress | |
method {cisco | ietf | snap | multi} | Specifies the encapsulation method. The choices are as follows:
|
no-incoming | Use the map only to originate calls. |
no-outgoing | Do not originate calls when using the map. |
idle minutes | Specifies an idle timeout for calls other than the interface default; 0 minutes disables the idle timeout. |
reverse | Specifies reverse charging for outgoing calls. |
accept-reverse | Causes the router to accept incoming reverse-charged calls. If this option is not present, the router clears reverse charged calls unless the interface accepts all reverse charged calls. |
broadcast | Causes the router to direct any broadcasts sent through this interface to the specified X.121 address. This option also simplifies the configuration of OSPF; see "Usage Guidelines" for more detail. |
cug group-number | Specifies a closed user group number (from 1 to 99) for the mapping in an outgoing call. |
nvc count | Sets the maximum number of virtual circuits for this map/host. The default count is the x25 nvc setting of the interface. A maximum number of eight virtual circuits can be configured for each map. Compressed TCP may only use 1 virtual circuit. |
packetsize in-size out-size | |
windowsize in-size out-size | Proposes the packet count for input window (in-size) and output window (out-size) for an outgoing call. Both values typically are the same, must be in the range 1 to 127, and must be less than the value set by the x25 modulo command. |
throughput in out | |
transit-delay milliseconds | Specifies the transit delay value in milliseconds (0 to 65534) for an outgoing call, for networks that support transit delay. |
nuid username password | |
nudata string | |
rpoa name | Specifies the name defined by the x25 rpoa command for a list of transit RPOAs to use in outgoing Call Request packets. |
passive | Specifies that the X.25 interface should send compressed outgoing TCP datagrams only if they were already compressed when they were received. This option is available only for compressed TCP maps. |
The following example maps IP address 131.08.2.5 to X.121 address 000000010300. The broadcast keyword directs any broadcasts sent through this interface to the specified X.121 address.
interface serial 0
x25 map ip 131.08.2.5 000000010300 broadcast
The following example specifies an RPOA name to be used when originating connections:
x25 rpoa green_list 23 35 36
interface serial 0
x25 map ip 131.108.170.26 10 rpoa green_list
The following example specifies a network user identifier (NUID) facility to send on calls originated for the address map:
interface serial 0 x25 map IP 131.108.174.32 2 nudata "Network User ID 35"
Strings can be quoted, but quotation marks are not required unless embedded blanks are present.
A dagger (†) indicates that the command is documented in another chapter.
ip ospf network†
show x25 map
x25 facility
x25 map bridge
x25 map cmns
x25 map compressedtcp
x25 rpoa
To configure an Internet-to-X.121 address mapping for bridging over X.25, use the x25 map bridge interface configuration command.
x25 map bridge x.121-address broadcast [option]
x.121-address | The X.121 address. |
broadcast | Required keyword for bridging over X.25. |
option | (Optional) Services t |