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Cisco IOS Release 12.0 Dial Solutions Command Reference
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About This Manual
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Using Cisco IOS Software
- Part 1: Dial-In Port Setup
- Part 2: Dial-In Terminal Service & Remote Node Config
- Part 3: Dial-on-Demand Routing
- Part 4: Dial Backup
- Part 5: NASI Client Commands
- Part 6: Large-Scale Dial Solutions
- Part 7: Cost-Control Solutions
- Part 8: Virtual Private Dialup Networks
- Part 9: Other Network Traffic on ISDN Channels
- Part 10: Dial-Related Addressing Services
- Part 11: Appendixes
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Index
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Table Of Contents
Asynchronous PPP and SLIP Commands
Asynchronous PPP and SLIP Commands
Point-to-Point Protocol (PPP) and Serial Line Internet Protocol (SLIP) define methods of sending IP packets over standard EIA/TIA-232 asynchronous serial lines with minimum line speeds of 1200 baud. This chapter describes the commands used to configure your router to enable PPP and SLIP on asynchronous interfaces.
Using PPP or SLIP encapsulation over asynchronous lines is an inexpensive way of connecting PCs to a network. PPP and SLIP over asynchronous dial-up modems allow a home computer to be connected to a network without the cost of a leased line. Dial-up PPP and SLIP links can also be used for remote sites that need only occasional remote node or backup connectivity. Both public-domain and vendor-supported PPP and SLIP implementations are available for a variety of computer applications.
Use the commands in this chapter to configure PPP and SLIP on your router. For configuration information and examples, refer to the chapter "Configuring Asynchronous PPP and SLIP" in the Dial Solutions Configuration Guide.
Note
Some commands previously documented in this chapter have been replaced by new commands. Although these commands continue to perform their normal functions in the current release, support for these commands will cease in future releases.
async mode dedicated
To place a line into dedicated asynchronous mode using SLIP or PPP encapsulation, use the async mode dedicated interface configuration command. To return the line to interactive mode, use the no form of this command.
async mode dedicated
no async mode dedicatedSyntax Description
This command has no arguments or keywords.
Default
Asynchronous mode is disabled.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
With dedicated asynchronous network mode, the interface will use either SLIP or PPP encapsulation, depending on which encapsulation method is configured for the interface. An EXEC prompt does not appear, and the router is not available for normal interactive use.
If you configure a line for dedicated mode, you will not be able to use the async dynamic address command, because there is no user prompt.
Example
The following example assigns an IP address to an asynchronous line and places the line into network mode. Setting the stop bits to 1 enhances performance.
interface async 4async default ip address 172.31.7.51async mode dedicatedencapsulation slipline 20location Joe's computerstopbits 1speed 115200Related Commands
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async mode interactive
To return a line that has been placed into dedicated asynchronous network mode to interactive mode, thereby enabling the slip and ppp EXEC commands, use the async mode interactive interface configuration command. To prevent users from implementing SLIP and PPP at the EXEC level, use the no form of this command.
async mode interactive
no async mode interactiveSyntax Description
This command has no arguments or keywords.
Default
Asynchronous mode is disabled.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Interactive mode enables the slip and ppp EXEC commands. In dedicated mode, there is no user EXEC level. The user does not enter any commands, and a connection is automatically established when the user logs in, according to the configuration.
Example
The following example places async interface 6 into interactive asynchronous mode:
interface async 6async default ip address 172.31.7.51async mode interactiveip unnumbered ethernet 0Related Commands
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autoselect
To configure a line to start an ARA, PPP, or SLIP session, use the autoselect line configuration command. Use the no form of this command to disable this function on a line.
autoselect {arap | ppp | slip | during-login}
no autoselectSyntax Description
Default
ARA session
Command Mode
Line configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3. The no autoselect command and the during-login command first appeared in Cisco IOS Release 11.0.
This command eliminates the need for users to enter an EXEC command to start an ARA, PPP, or SLIP session.
Note
The autoselect command configures the Cisco IOS software to identify the type of connection being requested. For example, when a user on a Macintosh running ARA selects the Connect button, the Cisco IOS software automatically starts an ARAP session. If, on the other hand, the user is running SLIP or PPP and uses the autoselect ppp or autoselect slip command, the Cisco IOS software automatically starts a PPP or SLIP session, respectively. This command is used on lines making different types of connections.
A line that does not have autoselect configured views an attempt to open a connection as noise. The router does not respond and the user client times out.
Note
Examples
The following example enables ARA on a line:
line 3arap enableautoselect arapThe following example enables PPP on a line:
line 7autoselect pppThe following example enables ARA on a line and allows logins from users with a modified CCL script and an unmodified script to log in:
line 3arap enableautoselect arapautoselect during-loginarap noguest if-neededRelated Commands
You can use the master indexes or search online to find documentation of related commands.
arap use-tacacs
ppp authentication chap
ppp authentication pap
ppp use-tacacsencapsulation
To configure SLIP or PPP encapsulation as the default on an asynchronous interface, use the encapsulation interface configuration command. To disable encapsulation, use the no form of this command.
encapsulation {slip | ppp}
no encapsulation {slip | ppp}Syntax Description
Default
SLIP encapsulation is enabled by default.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
On lines configured for interactive use, encapsulation is selected by the user when they establish a connection with the slip or ppp EXEC command.
IP Control Protocol (IPCP) is the part of PPP that brings up and configures IP links. After devices at both ends of a connection communicate and bring up PPP, they bring up the control protocol for each network protocol that they intend to run over the PPP link such as IP or IPX. If you have problems passing IP packets and the show interface command shows that line is up, use the negotiations command to see if and where the negotiations are failing. You might have different versions of software running, or different versions of PPP, in which case you might need to upgrade your software or turn off PPP option negotiations. All IPCP options as listed in RFC 1332 are supported on asynchronous lines. Only Option 2, TCP/IP header compression, is supported on synchronous interfaces.
PPP echo requests are used as keepalive packets to detect line failure. The no keepalive command can be used to disable echo requests. For more information about the no keepalive command, refer to the chapter "IP Services Commands" in the Networking Protocols Command Reference, Part 1 and the chapter "Configuring IP Services" in the Networking Protocols Configuration Guide, Part 1.
In order to use SLIP or PPP, the Cisco IOS software must be configured with an IP routing protocol or with the ip host-routing command. This configuration is done automatically if you are using old-style slip address commands. However, you must configure it manually if you configure SLIP or PPP via the interface async command.
Note
Example
In the following example, async interface 1 is configured for PPP encapsulation.
router# configConfiguring from terminal, memory, or network [terminal]?Enter configuration commands, one per line. End with CNTL/Z.router(config)# interface async 1router(config-if)# encapsulation pppRelated Commands
You can use the master indexes or search online to find documentation of related commands.
keepalive
ip access-group
To configure an access list to be used for packets transmitted to and from the asynchronous host, use the ip access-group interface configuration command. To disable control over packets transmitted to or from an asynchronous host, use the no form of this command.
ip access-group access-list-number {in | out}
no ip access-group access-list-numberSyntax Description
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
With this command in effect, the IP destination address of each packet is run through the access list for acceptability then dropped or passed.
Example
The following example assumes that users are restricted to certain servers designated as SLIP or PPP servers, but that normal terminal users can access anything on the local network:
! access list for normal connectionsaccess-list 1 permit 172.16.0.0 0.0.255.255!! access list for SLIP packets.access-list 2 permit 172.16.42.55access-list 2 permit 172.16.111.1access-list 2 permit 172.16.55.99!! Specify the access listinterface async 6async dynamic addressip access-group 1 outip access-group 2 inip address
To set IP addresses for an interface, use the ip address interface configuration command. To remove the specified addresses, use the no form of this command.
ip address address mask [secondary]
no ip address address mask [secondary]Syntax Description
address
IP address.
mask
Network mask for the associated IP network.
secondary
(Optional) Specifies additional IP addresses.
Default
No IP addresses are specified.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
The subnet mask must be the same for all interfaces connected to subnets of the same network. Hosts can determine subnet masks using the Internet Control Message Protocol (ICMP) Mask Request message. The Cisco IOS software responds to this request with an ICMP Mask Reply message.
You can disable IP processing on a particular interface by removing its IP address with the no ip address interface configuration command. If the router detects another host using one of its IP addresses, it will print an error message on the console.
Example
In the example that follows, 172.16.1.27 is the primary address and 192.168.7.17 and 192.168.8.17 are secondary addresses for async interface 1:
interface async 1ip address 172.16.1.27 255.255.255.0ip address 192.168.7.17 255.255.255.0 secondaryip address 192.168.8.17 255.255.255.0 secondaryip tcp async-mobility server
To enable asychronous listening, which in turn allows TCP connections to TCP port 57, enter the ip tcp async-mobility server global configuration command. Enter the no form of this command to turn listening off.
ip tcp async-mobility server
no ip tcp async-mobility serverSyntax
This command has no keywords or arguments.
Default
Disabled. Asynchronous listening is turned off.
Mode
Global Configuration
Usage
This command first appeared in Cisco IOS Release 11.2.
After asynchronous listening is turned on by the ip tcp async-mobility server command, enter the tunnel host command to establish a network layer connection to a remote host. Both commands must be used to enable asynchronous mobility.
Example
The following example shows how to configure asynchronous mobility. The tunnel host command is used to establish a network layer connection with an IBM host called mktg.
5300# configure terminalEnter configuration commands, one per line. End with CNTL/Z.5300(config)# ip tcp async-mobility server5300(config)# exit5300#%SYS-5-CONFIG_I: Configured from console by console5300# tunnel ?WORD Address or hostname of a remote system5300# tunnel mktgRelated Commands
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tunnel
ip tcp header-compression
To configure TCP header compression on the asynchronous link, use the ip tcp header-compression interface configuration command. To disable header compression, use the no form of this command.
ip tcp header-compression [on | off | passive]
no ip tcp header-compressionSyntax Description
Default
Header compression is on.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Header compression data areas are initialized to handle up to 16 simultaneous TCP connections. Currently, you cannot change this number. You can only turn header compression on or off or use the passive keyword.
On lines configured for PPP encapsulation, the keywords passive and on cause the same behavior because, before attempting header compression, PPP automatically negotiates whether compression is available at each end of the connection.
There are two ways to implement header compression when the line is configured for ip tcp header-compression passive:
•
•
If a line is configured for passive header compression and you use the slip or ppp EXEC command to enter asynchronous mode, you will see that the interface is set to match the compression status used by the host at the other end of the asynchronous line.
router> slip 10.0.0.1Password:Entering SLIP mode.Interface IP address is 10.0.0.1, MTU is 1500 bytesHeader compression will match your system.The message "Header compression will match your system" indicates that the interface is set to match the compression status used by the host at the other end of the asynchronous line. If the line was configured to have header compression on, this line would read "Header compression is On."
Example
The following example enables Van Jacobson TCP header compression. The passive keyword prevents transmission of compressed packets until a compressed packet arrives from the IP link. Notice that asynchronous routing and dynamic addressing are also enabled.
interface async 6 async dynamic routing async dynamic address ip tcp header-compression passiveRelated Commands
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ppp
slip
slip default
slip /compressedip unnumbered
To conserve network resources, use the ip unnumbered interface configuration command. To disable unnumbered interfaces, use the no form of this command.
ip unnumbered type number
no ip unnumberedSyntax Description
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
You must use either the ip address or ip unnumbered command to provide the local address for an interface.
Unnumbered interfaces do not have an address. Network resources are conserved because fewer network numbers are used and routing tables are smaller.
Whenever the unnumbered interface generates a packet (for example, a routing update), it uses the address of the specified interface as the source address of the IP packet. It also uses the address of the specified interface to determine which routing processes are sending updates over the unnumbered interface. Restrictions include the following:
•
•
•
Example
The following example configures async interface 6 as unnumbered:
interface async 6ip unnumbered ethernet 0Related Commands
You can use the master indexes or search online to find documentation of related commands.
ipx compression cipx
To enable compression of IPX packet headers in a PPP session, use the ipx compression cipx interface configuration command. To disable compression of IPX packet headers in a PPP session, use the no form of this command.
ipx compression cipx number-of-slots
no ipx compression cipxSyntax Description
Default
No compression of IPX packets during a PPP session.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1.
This interface configuration command enables IPX header compression on PPP links.
Example
The following example enables IPX header compression for PPP:
encapsulation pppipx compression cipx 128Related Commands
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show ipx compression
ipx ppp-client
To enable a non-routing IPX client to connect to an asynchronous interface, the interface must be associated with a loopback interface configured to run IPX. To permit such connections, use the ipx ppp-client interface configuration command. To disable a non-routing IPX client, use the no form of this command.
ipx ppp-client loopback number
no ipx ppp-client loopback numberSyntax Description
loopback
Loopback interface configured with a unique IPX network number.
number
Number of the loopback interface.
Default
IPX client connections are not permitted over PPP.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1.
This command enables IPX clients to log into the router from a device running a virtual terminal protocol, then issue the PPP command at the EXEC prompt to connect to a remote device.
You must first configure a loopback interface with a unique IPX network number. The loopback interface is then assigned to an asynchronous interface, which permits IPX clients to connect to the asynchronous interface.
Example
The following example configures IPX to run over PPP on asynchronous interface 3:
ipx routing 0000.0c07.b509interface loopback0no ip addressipx network 544ipx sap-interval 2000interface ethernet0ip address 172.21.14.64ipx network AC150E00ipx encapsulation SAPinterface async 3ip unnumbered ethernet0encapsulation pppasync mode interactiveasync default ip address 172.18.1.128ipx ppp-client loopback0ipx sap-interval 0Related Commands
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interface loopback
ipx networkpeer default ip address
Use the peer default ip address interface configuration command to specify an IP address, an address from a specific IP address pool, or an address from the DHCP mechanism to be returned to a remote peer connecting to this interface. This command sets the address used on the remote (PC) side. Use the no form of this command to disable a prior peer IP address pooling configuration on an interface.
To remove the default address from your configuration, use the no form of this command also.
peer default ip address {ip-address | dhcp | pool [pool-name]}
no peer default ip addressSyntax Description
Default
pool
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.0.
This command applies to point-to-point interfaces that support the PPP or SLIP encapsulation.
Note
This command allows an administrator to configure all possible address pooling mechanisms on a interface-by-interface basis. The peer default ip address command can be used to override the Global Default Mechanism defined by the ip address-pool command on an interface-by-interface basis.
For all interfaces not configured with a peer default IP address mechanism (equivalent to selecting the peer default ip address pool command), the router uses the Global Default Mechanism that is defined by the ip address-pool command.
If you select the peer default ip address pool pool-name command, then the router uses the locally configured pool on this interface and does not follow the Global Default Mechanism.
If you select the peer default ip address ip-address form of this command, the specified IP address is assigned to any peer connecting to this interface and any Global Default Mechanism is overridden for this interface.
If you select the peer default ip address dhcp form of this command, the DHCP proxy-client mechanism is used by default on this interface and any Global Default Mechanism is overridden for this interface.
Example
The following example specifies address 192.31.7.51 for async interface 6:
line 20speed 115200interface async 6peer default ip address 192.31.7.51Related Commands
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async dynamic address
ppp
To start an asynchronous connection using PPP, use the ppp EXEC command.
ppp {/default | {remote-ip-address | remote-name} [@tacacs-server]} [/routing]
Syntax Description
Command Mode
EXEC
Usage Guidelines
This command first appeared in a release prior to Cisco IOS Release 10.0.
When you connect from a remote node computer to an EXEC session on the access server and want to connect from the access server to a device on the network, issue the ppp command.
If you specify an address for the TACACS server (either /default or tacacs-server), the address must be the first parameter in the command after you type ppp. If you do not specify an address or enter default, you are prompted for an IP address or host name. You can enter default at this point.
To terminate a session, disconnect from the device on the network using the command specific to that device. Then, exit from the EXEC by using the exit command.
Example
The following example shows a line that is in asynchronous mode using PPP encapsulation (see ). The PC's name is ntpc—assuming that the name ntpc is in the Domain Naming System (DNS) so that it can be resolved to a real IP address). The PC must be running a terminal emulator program.
router> ppp ntpc@server1Figure 4 Using the PPP EXEC Command
ppp caller name
To set the caller option when no Calling Line Identification (CLID) is available, use the ppp caller name command in interface configuration mode. To remove the name, use the no form of this command.
ppp caller name name
no ppp caller name name
Syntax Description
Defaults
Command is disabled by default.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
This command sets the username used when the CLID is not available. This username is used only in the case where the ppp dnis command is configured and the CLID is not available.
Example
The following example shows how to configure a call to user1:
interface Serial0:15description "PRI D channel"ip unnumbered Loopback0encapsulation pppno keepalivedialer pool-member 1 max-link 1isdn switch-type primary-net5isdn incoming-voice modemno fair-queueno cdp enableppp caller name user1ppp authentication pap chap callin USERS&TUNNELSppp chap hostname oshRelated Commands
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ppp dnis
ppp dnis
To configure a set of dialed number identification service (DNIS) numbers to check an incoming call against to automatically authenticate and authorize a user, use the ppp dnis command in interface configuration mode. To remove the numbers, use the no form of this command.
ppp dnis DNIS-numbers
no ppp dnis DNIS-numbers
Syntax Description
Defaults
Command is disabled by default.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
This command enables a method of authenticating and authorizing a user based on the DNIS. The DNIS is the number dialed by the user. If the dialed number for this session matches one of the numbers configured in the ppp dnis command, the user is automatically authenticated and authorized for the session. Any other configured PPP authentication is not performed. In the case of DNIS authentication, the Calling Line Identification (CLID) is used as the username. If the CLID is unavailable, the username is the name configured with the ppp caller name command. If neither the CLID nor a caller name is configured, the username will automatically be set to "no-clid."
Example
The following example shows how to set the DNIS for a call:
interface Serial0:15description "PRI D channel"ip unnumbered Loopback0encapsulation pppno keepalivedialer pool-member 1 max-link 1isdn switch-type primary-net5isdn incoming-voice modemno fair-queueno cdp enableppp dnis 13693 132ppp authentication pap chap callin USERS&TUNNELSppp chap hostname oshRelated Commands
You can use the master indexes or search online to find documentation of related commands.
ppp caller name
ppp iphc max-header
To set the maximum size of the largest IP header that may be compressed when configuring Internet Protocol Header Compression (IPHC) control options over PPP, use the ppp iphc max-header command in interface configuration mode. To change the configuration, use the no form of this command.
ppp iphc max-header bytes
no ppp iphc max-header bytes
Syntax Description
bytes
Maximum size, in bytes, of the largest IP header that may be compressed. The range is from 60 to 168 bytes, and the default is 168 bytes.
Defaults
168 bytes
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
There are two types of IP header compression used over PPP: Van Jacobsen header compression defined in RFC 1332 and enabled with the ip tcp header-compression command, and IPHC defined in RFC 2509 and enabled with the ip rtp header-compression command. The ppp iphc set of commands controls parameters that pertain to the form of IPHC described in RFC 2509.
The IPHC specification allows low speed links to run more efficiently by reducing the size of the IP headers as transmitted on the link. IPHC supports compressed Real-Time Transport Protocol (cRTP), compressed User Datagram Protocol (cUDP), and compressed Transaction Control Protocol (cTCP).
An IPHC-enabled interface sends only changes to the header instead of sending the entire header with every packet. At the beginning of a transmission, the transmitting end (the compressor) sends a full header packet to the receiving end (the decompressor). After the initial packet is sent, the compressor sends all other packets with headers that contain only the differences between them and the original full header. The decompressor maintains a copy of the original full header and reconstructs all the other packet headers by adding the changes to them.
The header data that is different with each packet is referred to as the session state, and is identified by a session ID or connection ID.
When the decompressor receives a compressed packet, it reconstructs the packet header by adding the difference to the saved uncompressed header. Typically, IPHC enables the header to be compressed to two bytes (four bytes if UDP checksums are used).
The following fields in a packet header usually remain the same throughout a transmission:
•
•
•
The following fields in a packet header usually change during a transmission:
•
•
•
•
•
Example
The following example shows how to change the maximum size of the largest IP header that may be compressed from the default of 168 bytes to 114 bytes:
interface Multilink1ip address 10.100.253.1 255.255.255.0no ip directed-broadcastno ip route-cacheip tcp header-compression iphc-formatno ip mroute-cachefair-queue 64 256 1000no cdp enableppp multilinkppp multilink fragment-delay 20ppp multilink interleavemultilink-group 1ip rtp header-compression iphc-formatip rtp priority 16384 50 64ppp iphc max-header 114ppp iphc max-time 10ppp iphc max-period 512Related Commands
You can use the master indexes or search online to find documentation of related commands.
ip rtp header-compression
ip tcp header-compression
ppp iphc max-period
ppp iphc max-timeppp iphc max-period
To set the maximum number of compressed packets that can be sent before a full header when configuring Internet Protocol Header Compression (IPHC) control options over PPP, use the ppp iphc max-period command in interface configuration mode. To change the configuration, use the no form of this command.
ppp iphc max-period packets
no ppp iphc max-period packets
Syntax Description
packets
Maximum number of compressed packets that can be sent before a full header. The range is from 1 to 65,535 packets, and the default is 256 packets.
Defaults
256 packets
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
There are two types of IP header compression used over PPP: Van Jacobsen header compression, which is defined in RFC 1332, and a newer compression type described in RFC 2509. The ppp iphc set of commands controls parameters that pertain to the form of IPHC described in RFC 2509.
The IPHC specification allows low speed links to run more efficiently when IP headers are extremely large. IPHC supports compressed Real-Time Transport Protocol (cRTP), compressed User Datagram Protocol (cUDP), and compressed Transaction Control Protocol (cTCP).
An IPHC-enabled interface sends only changes to the header instead of sending the entire header with every packet. At the beginning of a transmission, the transmitting end (the compressor) sends a full header packet to the receiving end (the decompressor). After the initial packet is sent, the compressor sends all other packets with headers that contain only the differences between them and the original full header. The decompressor maintains a copy of the original full header and reconstructs all the other packet headers by adding the changes to them.
The header data that is different with each packet is referred to as the session state, and is identified by a session ID or connection ID.
When the decompressor receives a compressed packet, it reconstructs the packet header by adding the difference to the saved uncompressed header. Typically, IPHC enables the header to be compressed to two bytes (four bytes if UDP checksums are used).
The following fields in a packet header usually remain the same throughout a transmission:
•
•
•
The following fields in a packet header usually change during a transmission:
•
•
•
•
•
The ppp iphc max-period command is specifically related to an IPHC frame format known as compressed_non_TCP. The recovery of lost compressed_non_TCP frames on lossy links is much improved by allowing more full headers to flow and by configuring less compression.
Example
The following example shows how to increase the maximum number of compressed packets that can be sent before a full header from 256 to 512 packets when configuring IPHC control options over PPP:
interface Multilink1ip address 10.100.253.1 255.255.255.0no ip directed-broadcastno ip route-cacheip tcp header-compression iphc-formatno ip mroute-cachefair-queue 64 256 1000no cdp enableppp multilinkppp multilink fragment-delay 20ppp multilink interleavemultilink-group 1ip rtp header-compression iphc-formatip rtp priority 16384 50 64ppp iphc max-header 114ppp iphc max-time 10ppp iphc max-period 512Related Commands
You can use the master indexes or search online to find documentation of related commands.
ip rtp header-compression
ip tcp header-compression
ppp iphc max-header
ppp iphc max-timeppp iphc max-time
To set the maximum time allowed between full headers when configuring Internet Protocol Header Compression (IPHC) control options over PPP, use the ppp iphc max-time command in interface configuration mode. To change the configuration, use the no form of this command.
ppp iphc max-time seconds
no ppp iphc max-time seconds
Syntax Description
seconds
Maximum time, in seconds, allowed between full headers. The range is from 1 to 255 seconds, and the default is 5 seconds.
Defaults
5 seconds
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
There are two forms of IP header compression used over PPP: Van Jacobsen header compression, which is defined in RFC 1332, and a newer form of compression described in RFC 2509. The ppp iphc set of commands controls parameters that pertain to the form of IPHC described in RFC 2509.
The IPHC specification allows low speed links to run more efficiently by reducing the size of IP headers as transmitted on the link. IPHC supports compressed Real-Time Transport Protocol (cRTP), compressed User Datagram Protocol (cUDP), and compressed Transaction Control Protocol (cTCP).
An IPHC-enabled interface sends only changes to the header instead of sending the entire header with every packet. At the beginning of a transmission, the transmitting end (the compressor) sends a full header packet to the receiving end (the decompressor). After the initial packet is sent, the compressor sends all other packets with headers that contain only the differences between them and the original full header. The decompressor maintains a copy of the original full header and reconstructs all the other packet headers by adding the changes to them.
The header data that is different with each packet is referred to as the session state, and is identified by a session ID or connection ID.
When the decompressor receives a compressed packet, it reconstructs the packet header by adding the difference to the saved uncompressed header. Typically, IPHC enables the header to be compressed to two bytes (four bytes if UDP checksums are used).
The following fields in a packet header usually remain the same throughout a transmission:
•
•
•
The following fields in a packet header usually change during a transmission:
•
•
•
•
•
The ppp iphc max-time command is specifically related to an IPHC frame format known as compressed_non_TCP. The recovery of lost compressed_non_TCP frames on lossy links is much improved by allowing more full headers to flow and by configuring less compression.
Example
The following example shows how to change the number of compressed packets that can be sent before a full header from the default 5 seconds to 10 seconds:
interface Multilink1ip address 10.100.253.1 255.255.255.0no ip directed-broadcastno ip route-cacheip tcp header-compression iphc-formatno ip mroute-cachefair-queue 64 256 1000no cdp enableppp multilinkppp multilink fragment-delay 20ppp multilink interleavemultilink-group 1ip rtp header-compression iphc-formatip rtp priority 16384 50 64ppp iphc max-header 114ppp iphc max-time 10ppp iphc max-period 512Related Commands
You can use the master indexes or search online to find documentation of related commands.
ip rtp header-compression
ip tcp header-compression
ppp iphc max-header
ppp iphc max-timeppp lcp fast-start
To allow a Point-to-Point (PPP) interface to respond immediately to incoming packets once a connection is established, use the ppp lcp fast-start interface configuration command. To specify that PPP delay before responding, use the no form of this command.
ppp lcp fast-start
no ppp lcp fast-start
Syntax Description
This command has no arguments or keywords.
Default
Default is enabled.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
Some systems, typically those with external modems, may have problems with slow or electrically noisy hardware. If the no ppp lcp fast-start command is specified, PPP starts a debounce timer and waits for it to expire before attempting to communicate with the peer system, thereby reducing the probability of a false start on the interface.
If the no ppp lcp fast-start command is not specified, PPP will not use a debounce timer and will respond immediately to incoming packets once a connection is made.
The default fast-start enabled state should not be disabled unless there is a problem with slow or electronically noisy hardware. This setting prevents PPP from waiting for a debounce timer to expire before responding to inbound frames.
Example
The following example disables fast start:
no ppp lcp fast-startppp ms-chap refuse
To refuse Microsoft Challenge Handshake Authentication Protocol (MS-CHAP) authentication from peers requesting it, use the ppp ms-chap refuse command in interface configuration mode. To allow MS-CHAP authentication, use the no form of this command.
ppp ms-chap refuse [callin]
no ppp ms-chap refuse [callin]
Syntax Description
Defaults
This command is disabled by default.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
This command specifies that MS-CHAP authentication is disabled for all calls, meaning that all attempts by the peer to force the user to authenticate using MS-CHAP will be refused. If the callin keyword is used, MS-CHAP authentication is disabled for incoming calls from the peer, but will still be performed on outgoing calls to the peer.
If outbound Password Authentication Protocol (PAP) has been enabled (using the ppp pap sent-username command), PAP will be suggested as the authentication method in the refusal packet.
Example
The following example shows how to disable MS-CHAP authentication if a peer calls in requesting MS-CHAP authentication. The method of encapsulation on interface ISDN BRI number 0 is PPP.
interface bri 0encapsulation pppppp ms-chap refuseRelated Commands
You can use the master indexes or search online to find documentation of related commands.
aaa authentication ppp
ppp authentication
ppp authentication ms-chap-v2
ppp chap password
ppp chap wait
ppp pap sent-usernameppp ms-chap-v2 refuse
To refuse Microsoft Challenge Handshake Authentication Protocol (MS-CHAP) version 2 authentication from peers requesting it, use the ppp ms-chap-v2 refuse command in interface configuration mode. To allow MS-CHAP version 2 authentication, use the no form of this command.
ppp ms-chap-v2 refuse [callin]
no ppp ms-chap-v2 refuse [callin]
Syntax Description
Defaults
This command is disabled by default.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
This command specifies that MS-CHAP version 2 authentication is disabled for all calls, meaning that all attempts by the peer to force the user to authenticate using MS-CHAP version 2 will be refused. If the callin keyword is used, MS-CHAP version 2 authentication is disabled for incoming calls from the peer, but will still be performed on outgoing calls to the peer.
If outbound Password Authentication Protocol (PAP) has been enabled (using the ppp pap sent-username command), PAP will be suggested as the authentication method in the refusal packet.
Example
The following example shows how to disable MS-CHAP version 2 authentication if a peer calls in requesting MS-CHAP version 2 authentication. The method of encapsulation on interface ISDN BRI number 0 is PPP.
interface bri 0encapsulation pppppp ms-chap-v2 refuseRelated Commands
You can use the master indexes or search online to find documentation of related commands.
aaa authentication ppp
ppp authentication
ppp authentication ms-chap
ppp chap password
ppp chap wait
ppp pap sent-usernameservice old-slip-prompts
To provide backward compatibility for client software scripts expecting SLIP and PPP dialogs to be formatted with software release 9.1 or earlier, use the service old-slip-prompts global configuration command. Use the no form of this command to disable this function.
service old-slip-prompts
no service old-slip-promptsSyntax Description
This command has no arguments or keywords.
Default
The prompts and information transmitted by SLIP and PPP are formatted with the current release of Cisco IOS software.
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1.
Example
The following example shows the output of a SLIP command after service old-slip-prompts is enabled:
router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.router(config)# service old-slip-promptsrouter(config)# exitrouter# slipIP address or hostname: 2.2.2.2Entering SLIP mode.Your IP address is 2.2.2.2. MTU is 1500 bytesshow ipx compression
To show the current status and statistics of IPX header compression during PPP sessions, use the show ipx compression EXEC command.
show ipx compression detail int-spec
Syntax Description
Table 113
Async
Asynchronous interface.
Ethernet
Ethernet IEEE 802.3 interface.
Null
Null interface.
Serial
WAN serial interface.
Interface Types
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1.
Related Commands
You can use the master indexes or search online to find documentation of related commands.
ipx compression cipx
show ipx interfaceslip
To start a serial connection to a remote host by using SLIP, use the slip EXEC command.
slip [/default] {remote-ip-address | remote-name} [@tacacs-server] [/routing]} [/compressed]
Syntax Description
Command Mode
EXEC
Usage Guidelines
This command first appeared in a release prior to Cisco IOS Release 10.0.
When you connect from a remote node computer to the EXEC facility on a router and want to connect from the router to a device on the network, issue the slip command.
If you specify an address for the TACACS server by using /default or tacacs-server, the address must be the first parameter in the command after you enter slip. If you do not specify an address or enter /default, you are prompted for an IP address or host name. You can enter /default at this point.
If you do not use the tacacs-server argument to specify a TACACS server for SLIP address authentication, the TACACS server specified at login (if any) is used for the SLIP address query.
To optimize bandwidth on a line, SLIP enables compression of the SLIP packets using Van Jacobson TCP header compression as defined in RFC 1144.
Your system administrator must configure the system with the ip tcp header-compression passive command for the /compressed command option to be valid in EXEC mode. The ip tcp header-compression command forces header compression on or off. The default is to not compress the packets. The configuration file must have header compression on and the slip /compressed EXEC command must be entered for header compression to occur.
To terminate a session initiated with the slip command, disconnect from the device on the network using the command specific to that device. Then, exit from the EXEC by using the exit command.
Examples
The following example makes a connection when a default IP address is assigned. Once a correct password is entered, you are placed in SLIP mode, and the IP address is displayed.
router> slip Password:Entering SLIP mode.Your IP address is 192.31.7.28, MTU is 1524 bytesThe following example illustrates the prompts displayed and the response required when you use dynamic addressing to assign the SLIP address:
router> slip IP address or hostname? 192.31.6.15Password:Entering SLIP modeYour IP address is 192.31.6.15, MTU is 1524 bytesIn the preceding example, the address 192.31.6.15 has been assigned as the default. Password verification is still required before SLIP mode can be enabled.
router> slip /default Password:Entering SLIP modeYour IP address is 192.31.6.15, MTU is 1524 bytesThe following example illustrates the implementation of header compression on the interface with the IP address 128.66.2.1:
router> slip 128.66.2.1 /compressedPassword:Entering SLIP mode.Interface IP address is 128.66.2.1, MTU is 1500 bytes.Header compression will match your system.In the preceding example, the interface is configured for ip tcp header-compression passive, which permits the user to enter the /compressed keyword at the EXEC mode prompt. The message "Header compression will match your system" indicates that the user specified compression. If the line was configured for ip tcp header-compression on, this line would read "Header compression is On."
The following example specifies a TACACS server named server1 for address authentication:
router> slip 1.0.0.1@server1Password:Entering SLIP mode.Interface IP address is 1.0.0.1, MTU is 1500 bytesHeader compression will match your system.
