- Introduction
- A through C
- D through E
- fdl through frame-relay lapf n200
- frame-relay lapf n201 through fr-atm connect dlci
- H through L
- M through R
- sequencing through show rgf statistics
- show smds addresses through waas export
- x25 accept-reverse through x25 pvc (XOT)
- x25 pvc rbp local through xot access-group
- hello
- hidden
- hostname (L2TP)
- inarp (Frame Relay VC-bundle-member)
- interface fr-atm
- interface mfr
- interface serial multipoint
- interworking
- ip dfbit set
- ip local interface
- ip pmtu
- ip protocol
- ip tos (L2TP)
- ip ttl
- keepalive (LMI)
- l2 router-id
- l2 vfi autodiscovery
- l2tp cookie local
- l2tp cookie remote
- l2tp hello
- l2tp id
- l2tp-class
- lapb interface-outage
- lapb k
- lapb modulo
- lapb n1
- lapb n2
- lapb protocol
- lapb t1
- lapb t2
- lapb t4
- logging event frame-relay x25
- lz entropy-check
hello
To configure the interval used to exchange hello keepalive packets in a Layer 2 control channel, use the hello command in L2TP class configuration mode. To disable the sending of hello keepalive packets, use the no form of this command.
hello seconds
no hello seconds
Syntax Description
Command Default
The router sends hello keepalive packets at 60 second intervals.
Command Default
L2TP class configuration
Command History
Usage Guidelines
You can configure different values with the hello command on the router at each end of a Layer 2 control channel.
Examples
The following example sets an interval of 120 seconds between sending of hello keepalive messages in pseudowires that have been configured using the L2TP class configuration named "l2tp class1":
Router(config)# l2tp-class l2tp-class1
Router(config-l2tp-class)# hello 120
Related Commands
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l2tp-class |
Creates a template of L2TP control plane configuration settings that can be inherited by different pseudowire classes and enters L2TP class configuration mode. |
hidden
To hide the attribute-value (AV) pair values in Layer 2 Tunneling Protocol (L2TP) control messages, use the hidden command in L2TP class configuration mode. To unhide AV pairs, use the no form of this command.
hidden
no hidden
Syntax Description
This command has no arguments or keywords.
Command Default
L2TP AV pair hiding is disabled.
Command Modes
L2TP class configuration
Command History
Usage Guidelines
Use the hidden command to provide additional security for the exchange of control messages between provider edge routers in a Layer 2 Tunnel Protocol Version 3 (L2TPv3) control channel. Because username and password information is exchanged between devices in clear text, it is useful to encrypt L2TP AVP values with the hidden command.
In Cisco IOS Release 12.0(29)S and Cisco IOS Release 12.2(27)SBC, only the hiding of the cookie AVP is supported.
In Cisco IOS Release 12.0(29)S and Cisco IOS Release 12.2(27)SBC, this command was modified to function only with the authentication method configured using the digest secret command and keyword combination. AVP hiding is enabled only when both the digest secret command and keyword combination and the hidden command have been issued. If another method of authentication is also configured, such as Challenge Handshake Authentication Protocol (CHAP) style authentication configured with the L2TP class command authentication, AVP hiding will not be enabled.
If AVP hiding is configured, the session local cookie will be hidden when sent in incoming-call-request (ICRQ) and incoming-call-reply (ICRP) messages.
Whether or not AVP hiding is enabled, if a hidden AVP is received the AVP will be unhidden using the shared secret configured with the digest secret command and keyword combination. If no shared secret is configured, the AVP will not be unhidden and an error will be reported. If the M-bit is set in the received hidden AVP, the control channel or tunnel will be torn down.
Examples
The following example enables AVP hiding and encrypts AVPs in control messages in L2TPv3 pseudowires configured using the L2TP class configuration named l2tp class1:
Router(config)# l2tp-class l2tp-class1
Router(config-l2tp-class)# digest secret cisco hash sha
Router(config-l2tp-class)# hidden
Related Commands
hostname (L2TP)
To configure the hostname that the router will use to identify itself during Layer 2 Tunnel Protocol Version 3 (L2TPv3) authentication, use the hostname command in L2TP class configuration mode. To remove the hostname, use the no form of this command.
hostname name
no hostname name
Syntax Description
name |
Name used to identify the router during authentication. |
Command Default
No hostname is specified for L2TPv3 authentication.
Command Modes
L2TP class configuration
Command History
Usage Guidelines
If you do not use the hostname command, the hostname of the router is used for L2TPv3 authentication.
Examples
The following example configures the hostname yb2 for a provider edge router used at one end of an L2TPv3 control channel in an L2TPv3 pseudowire that has been configured using the L2TP class configuration named l2tp class1:
Router(config)# l2tp-class l2tp-class1
Router(config-l2tp-class)# hostname yb2
Related Commands
inarp (Frame Relay VC-bundle-member)
To override the default permanent virtual circuit (PVC) bundle member used for Inverse Address Resolution Protocol (ARP) and specify a different PVC bundle member to handle the Inverse ARP packets, use the inarp command in Frame Relay VC-bundle-member configuration mode. To disable Inverse ARP on the PVC bundle member, use the no form of this command.
inarp
no inarp
Syntax Description
This command has no arguments or keywords.
Defaults
Inverse ARP is handled by the PVC that handles precedence or EXP level 6 or DSCP level 63.
Command Modes
Frame Relay VC-bundle-member configuration
Command History
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|---|---|
12.2(13)T |
This command was introduced. |
12.2(28)SB |
This command was integrated into Cisco IOS Release 12.2(28)SB. |
Usage Guidelines
In each Frame Relay PVC bundle, Inverse ARP by default is handled by the PVC that handles precedence or EXP level 6 or DSCP level 63. In the default case, if the PVC handling Inverse ARP traffic goes down, the Inverse ARP packets are diverted to the PVC that has been configured to handle the bumped traffic for precedence level 6 or DSCP level 63.
Inverse ARP packets arriving on PVCs that are not configured to handle Inverse ARP will be dropped.
If you override the default packet service levels and enable Inverse ARP on a PVC that handles a different precedence or DSCP level, and that PVC goes down, the Inverse ARP packets will be dropped even if another PVC accepts the bumped traffic from the failed PVC.
If the inarp command is entered on two different PVC bundle members, Inverse ARP traffic will be handled by the second entry.
Examples
The following example shows Inverse ARP enabled on PVC 250, which handles DSCP level 60:
interface serial 1/4.1 multipoint
frame-relay vc-bundle MP-4-dynamic
match dscp
pvc 100
dscp other
pvc 250
dscp 60
inarp
Related Commands
interface fr-atm
To create a Frame Relay-ATM Interworking interface on the Cisco MC3810 and to enter Frame Relay-ATM Interworking configuration mode, use the interface fr-atm command in global configuration mode. To delete the Frame Relay-ATM Interworking interface, use the no form of this command.
interface fr-atm number
no interface fr-atm number
Syntax Description
number |
The Frame Relay-ATM Interworking interface number. Range is from 0 to 20. |
Defaults
Frame Relay-ATM Interworking interface 20 is configured by default.
Command Modes
Global configuration
Command History
Usage Guidelines
This command applies to Frame Relay-ATM Interworking on the Cisco MC3810 only.
Use the interface fr-atm command to enter Frame Relay-ATM interworking interface configuration mode. When you issue this command for the first time, an interface number is created dynamically. You can configure up to 21 Frame Relay-ATM interworking interfaces.
Note 
The Cisco MC3810 provides only network interworking (FRF.5). The Cisco MC3810 can be used with service interworking (FRF.8), which is provided by the carrier's ATM network equipment.
Examples
The following example configures Frame Relay-ATM Interworking interface number 20:
interface fr-atm 20
Related Commands
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fr-atm connect dlci |
Maps a Frame Relay DLCI to an ATM virtual circuit descriptor for FRF.5 Frame Relay-ATM internetworking. |
interface mfr
To configure a multilink Frame Relay (MFR) bundle interface, use the interface mfr command in global configuration mode. To remove the bundle interface, use the no form of this command.
interface mfr number
no interface mfr number
Syntax Description
number |
Number that will uniquely identify this bundle interface. Range: 0 to 2147483647. |
Command Default
A Frame Relay bundle interface is not configured.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
Frame Relay encapsulation is the default encapsulation type for multilink Frame Relay bundle interfaces.
A bundle interface is a virtual interface that serves as the Frame Relay data link and performs the same functions as a physical interface. The bundle is made up of physical serial links, called bundle links. The bundle links within a bundle function as one physical link and one pool of bandwidth. Functionality that you want to apply to the bundle links must be configured on the bundle interface.
The no interface mfr command will work only if all bundle links have been removed from the bundle by using the no encapsulation frame-relay mfr command.
Examples
The following example shows the configuration of a bundle interface called "mfr0." The bundle identification (BID) name "BUNDLE-A" is assigned to the bundle. Serial interfaces 0 and 1 are assigned to the bundle as bundle links.
interface MFR0
frame-relay multilink bid BUNDLE-A
!
interface serial0
encapsulation frame-relay MFR0
!
interface serial1
encapsulation frame-relay MFR0
Related Commands
interface serial multipoint
To define a logical subinterface on a serial interface to support multiple logical IP subnetworks over Switched Multimegabit Data Service (SMDS), use the interface serial multipoint interface configuration command.
interface serial {interface | slot/port}.subinterface multipoint
Syntax Description
Defaults
This command has no default values.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command only for routers that need knowledge of multiple IP networks. Other routers can be configured with information only about their own networks. A period must be used to separate the interface or slot/port from the subinterface.
Examples
The following example configures serial interface 2 with multipoint logical subinterface 1:
interface serial 2.1 multipoint
The following example configures slot 2 port 0 with multipoint logical subinterface 1:
interface serial 2/0.1 multipoint
Related Commands
interworking
To enable the L2VPN Interworking feature, use the interworking command in pseudowire class configuration mode. To disable the L2VPN Interworking feature, use the no form of this command.
interworking {ethernet | ip | vlan}
no interworking {ethernet | ip | vlan}
Syntax Description
Defaults
L2VPN interworking is not enabled.
Command Modes
Pseudowire class configuration (config-pw)
Command History
Usage Guidelines
Table 17 shows which L2VPN Interworking features support Ethernet, IP, and VLAN types of interworking.
Examples
The following example shows a pseudowire class configuration that enables the L2VPN Interworking feature:
pseudowire-class ip-interworking
encapsulation mpls
interworking ip
Related Commands
ip dfbit set
To enable the Don't Fragment (DF) bit in the outer Layer 2 header, use the ip dfbit set command in pseudowire class configuration mode. To disable the DF bit setting, use the no form of this command.
ip dfbit set
no ip dfbit set
Syntax Description
This command has no arguments or keywords.
Command Default
On the Cisco 10720 Internet router and Cisco 12000 series Internet routers, the DF bit is on (enabled) by default. On other platforms, the DF bit is off (disabled) by default.
Command Modes
Pseudowire class configuration
Command History
Usage Guidelines
Use this command to set the DF bit on if, for performance reasons, you do not want tunneled packet reassembly to be performed on the router.
Note The no ip dfbit set command is not supported on the Cisco 10720 Internet router and Cisco 12000 series Internet routers.
Examples
The following example shows how to enable the DF bit in the outer Layer 2 header in pseudowires that were created from the pseudowire class named "ether-pw":
Router(config)# pseudowire-class ether-pw
Router(config-pw)# ip dfbit set
Related Commands
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ip pmtu (L2TP) |
Enables the discovery of a PMTU for Layer 2 traffic. |
pseudowire-class |
Specifies the name of an L2TP pseudowire class and enters pseudowire class configuration mode. |
ip local interface
To configure the IP address of the provider edge (PE) router interface to be used as the source IP address for sending tunneled packets, use the ip local interface command in pseudowire class configuration mode. To remove the IP address, use the no form of this command.
ip local interface interface-name
no ip local interface interface-name
Syntax Description
interface-name |
Name of the PE interface whose IP address is used as the source IP address for sending tunneled packets over a Layer 2 pseudowire. |
Command Default
No IP address is configured.
Command Modes
Pseudowire class configuration
Command History
Usage Guidelines
Use the same local interface name for all pseudowire classes configured between a pair of PE routers. It is highly recommended that you configure a loopback interface with this command. If you do not configure a loopback interface, the router will choose the "best available local address," which could be any IP address configured on a core-facing interface. This configuration could prevent a control channel from being established.
Note The interface configured with the ip local interface command must be a loopback interface on Cisco 12000 series Internet routers.
Note This command must be configured for pseudowire class configurations using Layer 2 Tunnel Protocol version 3 (L2TPv3) as the data encapsulation method.
Examples
The following example shows how to configure the IP address of the local Ethernet interface 0/0 as the source IP address for sending Ethernet packets through an L2TPv3 session:
Router(config)# pseudowire-class ether-pw
Router(config-pw)# ip local interface ethernet 0/0
Related Commands
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pseudowire-class |
Specifies the name of an L2TP pseudowire class and enters pseudowire class configuration mode. |
ip pmtu
To enable the discovery of the path maximum transmission unit (MTU) for Layer 2 traffic, use the ip pmtu command in VPDN group, VPDN template, or pseudowire class configuration mode. To disable path MTU discovery, use the no form of this command.
ip pmtu
no ip pmtu
Syntax Description
This command has no arguments or keywords.
Command Default
Path MTU discovery is disabled.
Command Modes
VPDN group configuration (config-vpdn)
VPDN template configuration (config-vpdn-templ)
Pseudowire class configuration (config-pw)
Command History
Usage Guidelines
When the ip pmtu command is enabled, the Don't Fragment (DF) bit is copied from the inner IP header to the Layer 2 encapsulation header.
Enabling the ip pmtu command triggers Internet Control Message Protocol (ICMP) unreachable messages that indicate fragmentation errors in the IP backbone network carrying the tunneled traffic. If an IP packet is larger than the MTU of any interface, it must pass through and the DF bit is set, the packet is dropped and an ICMP unreachable message is returned. The ICMP unreachable message indicates the MTU of the interface that was unable to forward the packet without fragmentation. This information allows the source host to reduce the size of the packet before retransmission, allowing it to fit through that interface.
Note When path MTU discovery (PMTUD) is enabled, VPDN deployments are vulnerable to Denial of Service (DoS) attacks that use crafted Internet Control Message Protocol (ICMP) "fragmentation needed and Don't Fragment (DF) bit set" (code 4) messages, also known as PMTUD attacks.
Crafted code 4 ICMP messages can be used to set the path MTU to an impractically low value. This will cause higher layer protocols to time out because of a very low throughput, even though the connection is still in the established state. This type of attack is classified as a throughput-reduction attack. When PMTUD is enabled, it is highly recommended that you use the vpdn pmtu command to configure a range of acceptable values for the path MTU to block PMTUD attacks.
Enabling PMTUD will decrease switching performance.
When issued in VPDN group configuration mode, the ip pmtu command enables any tunnel associated with the specified virtual private dial-up network (VPDN) group to participate in path MTU discovery.
When issued in VPDN template configuration mode, the ip pmtu command enables any tunnel associated with the specified VPDN template to participate in path MTU discovery.
When issued in pseudowire class configuration mode, the ip pmtu command enables any Layer 2 Tunnel Protocol Version 3 (L2TPv3) session derived from the specified pseudowire class configuration to participate in path MTU discovery.
Examples
The following example configures a VPDN group named dial-in on a Layer 2 Tunnel Protocol (L2TP) tunnel server and uses the ip pmtu command to specify that tunnels associated with this VPDN group will participate in path MTU discovery. The vpdn pmtu command is used to configure the device to accept only path MTU values ranging from 576 to 1460 bytes. The device will ignore code 4 ICMP messages that specify a path MTU outside of this range.
Router(config)# vpdn-group dial-in
Router(config-vpdn)# request-dialin
Router(config-vpdn-acc-in)# protocol l2tp
Router(config-vpdn-acc-in)# virtual-template 1
!
Router(config-vpdn)# l2tp security crypto-profile l2tp
Router(config-vpdn)# no l2tp tunnel authentication
Router(config-vpdn)# lcp renegotiation on-mismatch
Router(config-vpdn)# ip pmtu
!
Router(config)# vpdn pmtu maximum 1460
Router(config)# vpdn pmtu minimum 576
The following example shows how to enable the discovery of the path MTU for pseudowires that are created from the pseudowire class named ether-pw. The vpdn pmtu command is used to configure the device to accept only path MTU values ranging from 576 to 1460 bytes. The device will ignore code 4 ICMP messages that specify a path MTU outside of this range.
Router(config)# pseudowire-class ether-pw
Router(config-pw)# ip pmtu
!
Router(config)# vpdn pmtu maximum 1460
Router(config)# vpdn pmtu minimum 576
Related Commands
ip protocol
To configure the Layer 2 Tunnel Protocol (L2TP) or Universal Tunnel Interface (UTI) as the IP protocol used for tunneling packets in a Layer 2 pseudowire, use the ip protocol command in pseudowire class configuration mode. To remove the IP protocol configuration, use the no form of this command.
ip protocol {l2tp | uti | protocol-number}
no ip protocol {l2tp | uti | protocol-number}
Syntax Description
Command Default
The default IP protocol is L2TP.
Command Modes
Pseudowire class configuration
Command History
Usage Guidelines
Use the ip protocol command to ensure backward compatibility with routers running UTI. This command allows you to configure an L2TPv3 pseudowire between a router running L2TPv3 and a peer router running UTI.
Note You can use the ip protocol command only if you have already entered the encapsulation l2tpv3 command.
To configure L2TP as the IP protocol that is used to tunnel packets in an L2TPv3 pseudowire, you may enter 115, the IP protocol number assigned to L2TPv3, instead of l2tp in the ip protocol command.
To configure UTI as the IP protocol that is used to tunnel packets in an L2TPv3 pseudowire, you may enter 120, the IP protocol number assigned to UTI, instead of uti in the ip protocol command.
Note Interoperability in an L2TPv3 control channel between a router running UTI and a router configured for L2TPv3 encapsulation is supported only if you disable signaling using the protocol none command.
Examples
The following example shows how to configure UTI as the IP protocol used to tunnel packets in an L2TPv3 pseudowire created from the pseudowire class named "ether-pw":
Router(config)# pseudowire-class ether-pw
Router(config-pw)# encapsulation l2tpv3
Router(config-pw)# ip protocol uti
Related Commands
ip tos (L2TP)
To configure the Type of Service (ToS) byte in the header of Layer 2 tunneled packets, use the ip tos command in pseudowire class configuration mode. To disable a configured ToS value or IP ToS reflection, use the no form of this command.
ip tos {value value | reflect}
no ip tos {value value | reflect}
Syntax Description
Command Default
The default ToS value is 0.
Command Modes
Pseudowire class configuration
Command History
Usage Guidelines
The ip tos command allows you to manually configure the value of the ToS byte used in the headers of Layer 2 tunneled packets or to have the ToS value reflected from the IP header of the encapsulated packet.
Note The reflect option is not supported on the Cisco 10720 and Cisco 12000 series Internet routers.
Note IP ToS byte reflection functions only if traffic in an L2TPv3 session carries IP packets as its payload.
In addition, you can configure both IP ToS reflection and a ToS priority level (from 0 to 255) for a pseudowire class. In this case, the ToS value in the tunnel header defaults to the value you specify with the ip tos value value command. IP packets received on the Layer 2 interface and encapsulated into the L2TPv3 session have their ToS byte reflected into the outer IP session, overriding the default value configured with the ip tos value value command.
Examples
In the following example, the ToS byte in the headers of tunneled packets in Layer 2 tunnels created from the pseudowire class named "ether-pw" will be reflected from the ToS value in the header of each encapsulated IP packet:
Router(config)# pseudowire-class ether-pw
Router(config-pw)# ip tos reflect
Related Commands
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pseudowire-class |
Specifies the name of an L2TP pseudowire class and enters pseudowire class configuration mode. |
ip ttl
To configure the time-to-live (TTL) byte in the IP headers of Layer 2 tunneled packets, use the ip ttl command in pseudowire class configuration mode. To remove the configured TTL value, use the no form of this command.
ip ttl value
no ip ttl value
Syntax Description
value |
Value of the TTL byte in the IP headers of L2TPv3 tunneled packets. The valid values range from 1 to 255. The default value is 255. |
Command Default
The default value of the TTL byte is 255.
Command Modes
Pseudowire class configuration
Command History
Usage Guidelines
Use this command to set the Don't Fragment (DF) bit on if, for performance reasons, you do not want tunneled packet reassembly to be performed on the router.
Examples
The following example shows how to set the TTL byte to 100 in the IP header of Layer 2 tunneled packets in pseudowires that were created from the pseudowire class named "ether-pw":
Router(config)# pseudowire-class ether-pw
Router(config-pw)# ip ttl 100
Related Commands
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pseudowire-class |
Specifies the name of an L2TP pseudowire class and enters pseudowire class configuration mode. |
keepalive (LMI)
To enable the Local Management Interface (LMI) mechanism for serial lines using Frame Relay encapsulation, use the keepalive command in interface configuration mode. To disable this capability, use the no form of this command.
keepalive number
no keepalive
Syntax Description
Defaults
10 seconds
Command Modes
Interface configuration
Command History
Usage Guidelines
The keepalive command enables the keepalive sequence, which is part of the LMI protocol.
Note When booting from a network server over Frame Relay, you might need to disable keepalives.
Examples
The following example sets the keepalive timer on the server for a period that is two or three seconds faster (has a shorter interval) than the interval set on the keepalive timer of the Frame Relay switch. The difference in keepalive intervals ensures proper synchronization between the Cisco server and the Frame Relay switch.
interface serial 3
keepalive 8
Related Commands
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frame-relay lmi-t392dce |
Sets the polling verification timer on a DCE or NNI interface. |
l2 router-id
To specify a router ID for the provider edge (PE) router to use with Virtual Private LAN Services (VPLS) Autodiscovery pseudowires, use the l2 router-id command in L2 VFI configuration mode. To revert to the MPLS global router ID, use the no form of this command.
l2 router-id ip-address
no l2 router-id ip-address
Syntax Description
ip-address |
Router ID in IP address format. |
Defaults
The Layer 2 router ID is set to the Multiprotocol Label Switching (MPLS) global router ID.
Command Modes
L2 VFI configuration
Command History
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|---|---|
12.2(33)SRB |
This command was introduced. |
Usage Guidelines
You can configure an arbitrary value in the IP address format for each router. However, each router ID must be unique.
The Layer 2 router ID is used in the forward equivalence class (FEC) 129 encoding for pseudowire signaling It is also used in the network layer reachability information (NLRI) for peer discovery.
Examples
The following example specifies a Layer 2 router ID:
l2 router-id 10.1.1.1
Related Commands
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l2 vfi autodiscovery |
Enables the VPLS PE router to automatically discover other PE routers that are part of the same VPLS domain. |
l2 vfi autodiscovery
To enable the Virtual Private LAN Service (VPLS) provider edge (PE) router to automatically discover other PE routers that are part of the same VPLS domain, use the l2 vfi autodiscovery command in global configuration mode. To disable VPLS autodiscovery, use the no form of this command.
l2 vfi vfi-name autodiscovery
no l2 vfi vfi-name autodiscovery
Syntax Description
vfi-name |
Specifies the name of the virtual forwarding instance. The virtual forwarding instance (VFI) identifies a group of pseudowires that are associated with a virtual switching instance (VSI). |
Command Default
Layer 2 VFI autodiscovery is not enabled.
Command Modes
Global configuration
Command History
|
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|---|---|
12.2(33)SRB |
This command was introduced. |
Usage Guidelines
VPLS Autodiscovery enables each VPLS PE router to discover other PE routers that are part of the same VPLS domain. VPLS Autodiscovery also automatically detects when PE routers are added to or removed from the VPLS domain. Beginning with Cisco IOS Release 12.2(33)SRB, you no longer need to manually configure the VPLS neighbors and maintain the configuration when a PE router is added or deleted. However, you can still perform manual VPLS configuration even when you enable VPLS Autodiscovery.
Examples
The following example enables VPLS Autodiscovery on a PE router:
l2 vfi vfi2 autodiscovery
Related Commands
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l2 vfi manual |
Manually creates a Layer 2 VFI. |
l2tp cookie local
To configure the size of the cookie field used in the Layer 2 Tunnel Protocol Version 3 (L2TPv3) headers of incoming packets received from the remote provider edge (PE) peer router, use the l2tp cookie local command in xconnect configuration mode. To remove the configured cookie field parameters, use the no form of this command.
l2tp cookie local size low-value [high-value]
no l2tp cookie local size low-value [high-value]
Syntax Description
Command Default
No cookie value is included in the header of L2TP packets.
Command Modes
Xconnect configuration (config-if-xconn)
Command History
Usage Guidelines
The l2tp cookie local command specifies the values that the peer PE router includes in the cookie field in L2TPv3 headers of the packets it sends to the local PE router through an L2TPv3 session. These values are required in a static L2TPv3 session.
The cookie field is an optional part of an L2TPv3 header with a length of either 4 or 8 bytes. If you specify an 8-byte length, you must also enter a value for the high-value argument.
Note For the Cisco 10720 and Cisco 12000 series Internet routers, an 8-byte cookie must be configured with this command.
Examples
The following example shows how to configure the cookie field of 4 bytes starting at 54321 for the L2TPv3 headers in incoming tunneled packets that were sent from the remote PE peer:
Router(config)# interface Ethernet 0/0
Router(config-if)# xconnect 10.0.3.201 123 encapsulation l2tpv3 manual pw-class ether-pw
Router(config-if-xconn)# l2tp cookie local 4 54321
Related Commands
l2tp cookie remote
To configure the size of the cookie field used in the Layer 2 Tunnel Protocol Version 3 (L2TPv3) headers of outgoing packets sent from the local provider edge (PE) peer router, use the l2tp cookie remote command in xconnect configuration mode. To remove the configured cookie field parameters, use the no form of this command.
l2tp cookie remote size low-value [high-value]
no l2tp cookie remote size low-value [high-value]
Syntax Description
Command Default
No cookie value is included in the header of L2TP packets.
Command Modes
Xconnect configuration (config-if-xconn)
Command History
Usage Guidelines
The l2tp cookie remote command specifies the values that the local PE router includes in the cookie field in L2TPv3 headers of the packets it sends to the remote PE router through an L2TPv3 session. These values are required in a static L2TPv3 session.
The cookie field is an optional part of an L2TPv3 header with a length of either 4 or 8 bytes. If you specify an 8-byte length, you must also enter a value for the high-value argument.
Examples
The following example shows how to configure the cookie field of 4 bytes starting at 12345 for the L2TPv3 headers in outgoing tunneled packets sent to the remote PE peer:
Router(config)# interface Ethernet 0/0
Router(config-if)# xconnect 10.0.3.201 123 encapsulation l2tpv3 manual pw-class ether-pw
Router(config-if-xconn)# l2tp cookie remote 4 12345
Related Commands
l2tp hello
To specify the use of a hello keepalive setting contained in a specified Layer 2 Tunneling Protocol class configuration for a static Layer 2 Tunnel Protocol Version 3 (L2TPv3) session, use the l2tp hello command in xconnect configuration mode. To disable the sending of hello keepalive messages, use the no form of this command.
l2tp hello l2tp-class-name
no l2tp hello l2tp-class-name
Syntax Description
l2tp-class-name |
Specifies the L2TP class configuration in which the hello keepalive interval to be used for the L2TPv3 session is stored. |
Command Default
No hello keepalive messages are sent.
Command Modes
Xconnect configuration (config-if-xconn)
Command History
Usage Guidelines
Because a static L2TPv3 session does not use a control plane to dynamically negotiate control channel parameters, you must use the l2tp hello command to specify an L2TP class configuration that contains the interval for sending hello keepalive messages.
Examples
The following example shows how to configure the time interval for hello keepalive messages stored in the L2TP class configuration named l2tp-default for an Ethernet interface using the configuration settings stored in the pseudowire class named ether-pw:
Router(config)# interface Ethernet 0/0
Router(config-if)# xconnect 10.0.3.201 123 encapsulation l2tpv3 manual pw-class ether-pw
Router(config-if-xconn)# l2tp hello lt2p-defaults
Related Commands
l2tp id
To configure the identifiers used by the local and remote provider edge (PE) routers at each end of a Layer 2 Tunnel Protocol Version 3 (L2TPv3) session, use the l2tp id command in xconnect configuration mode. To remove the configured identifiers for local and remote sessions, use the no form of this command.
l2tp id local-session-id remote-session-id
no l2tp id local-session-ID remote-session-ID
Syntax Description
local-session-id |
The identifier used by the local PE router as its local session identifier. |
remote-session-id |
The identifier used by the remote PE router as its local session identifier. |
Command Default
No session identifiers are configured.
Command Modes
Xconnect configuration (config-if-xconn)
Command History
Usage Guidelines
The xconnect configuration that binds an attachment circuit to an L2TPv3 pseudowire is not complete without configured values for the local-session-id and remote-session-id arguments.
Examples
The following example shows how to configure the identifiers named 222 for the local PE router and 111 for the remote peer in an L2TPv3 session bound to an Ethernet circuit using the L2TPv3 configuration settings stored in the pseudowire class names ether-pw:
Router(config)# interface Ethernet 0/0
Router(config-if)# xconnect 10.0.3.201 123 encapsulation l2tpv3 manual pw-class ether-pw
Router(config-if-xconn)# l2tp id 222 111
Related Commands
l2tp-class
To create a template of Layer 2 Tunnel Protocol (L2TP) control plane configuration settings, which can be inherited by different pseudowire classes, and to enter L2TP class configuration mode, use the l2tp-class command in global configuration mode. To remove a specific L2TP class configuration, use the no form of this command.
l2tp-class [l2tp-class-name]
no l2tp-class l2tp-class-name
Syntax Description
l2tp-class-name |
(Optional) Name of the L2TP class. The name argument must be specified if you want to configure multiple sets of L2TP control parameters. |
Command Default
No L2TP classes are defined.
Command Modes
Global configuration (config)
Command History
Usage Guidelines
The l2tp-class l2tp-class-name command lets you configure an L2TP class template that consists of configuration settings used by different pseudowire classes. An L2TP class includes the following configuration settings:
•Hostname of local router used during Layer 2 authentication
•Authentication enabled
•Time interval used for exchange of hello packets
•Password used for control channel authentication
•Packet size of receive window
•Retransmission settings for control packets
•Time allowed to set up a control channel
The l2tp-class command enters L2TP class configuration mode, where L2TP control plane parameters are configured.
You must use the same L2TP class in the pseudowire configuration at both ends of a Layer 2 control channel.
Note For Cisco IOS Release 12.2(33)SCC and Cisco IOS Release 12.2(50)SQ, the commands listed under the Related Commands section are not valid.
Examples
The following example shows how to enter L2TP class configuration mode to create an L2TP class configuration template for a class named ether-pw:
Router(config)# l2tp-class ether-pw
Router(config-l2tp-class)#
Related Commands
lapb interface-outage
To specify the period for which a link will remain connected, even if a brief hardware outage occurs (partial Link Access Procedure, Balanced [LAPB] T3 timer functionality), use the lapb interface-outage interface configuration command.
lapb interface-outage milliseconds
Syntax Description
milliseconds |
Number of milliseconds (ms) a hardware outage can last without the protocol disconnecting the service. |
Defaults
0 ms, which disables this feature.
Command Modes
Interface configuration
Command History
Usage Guidelines
If a hardware outage lasts longer than the LAPB hardware outage period you select, normal protocol operations will occur. The link will be declared down, and when it is restored, a link setup will be initiated.
Examples
The following example sets the interface outage period to 100 ms. The link remains connected for outages equal to or shorter than that period.
encapsulation lapb dte ip
lapb interface-outage 100
Related Commands
lapb k
To specify the maximum permissible number of outstanding frames, called the window size, use the lapb k interface configuration command.
lapb k window-size
Syntax Description
window-size |
Frame count. Range: 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). |
Defaults
7 frames
Command Modes
Interface configuration
Command History
Usage Guidelines
If the window size is changed while the protocol is up, the new value takes effect only when the protocol is reset. You will be informed that the new value will not take effect immediately.
When using the Link Access Procedure, Balanced (LAPB) modulo 128 mode (extended mode), you must increase the window parameter k to send a larger number of frames before acknowledgment is required. This increase is the basis for the router's ability to achieve greater throughput on high-speed links that have a low error rate.
This configured value must match the value configured in the peer X.25 switch. Nonmatching values will cause repeated LAPB reject (REJ) frames.
Examples
The following example sets the LAPB window size (the k parameter) to 10 frames:
interface serial 0
lapb modulo
lapb k 10
Related Commands
|
|
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|---|---|
lapb modulo |
Specifies the LAPB basic (modulo 8) or extended (modulo 128) protocol mode. |
lapb modulo
To specify the Link Access Procedure, Balanced (LAPB) basic (modulo 8) or extended (modulo 128) protocol mode, use the lapb modulo interface configuration command.
lapb modulo modulus
Syntax Description
modulus |
Either 8 or 128. The value 8 specifies LAPB's basic mode; the value 128 specifies LAPB's extended mode. |
Defaults
Modulo 8
Command Modes
Interface configuration
Command History
Usage Guidelines
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, you must increase the window parameter k to send a larger number of frames before acknowledgment is required. This increase is the basis for the router's 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 takes effect only when the protocol is reset. You will be informed that the new value will not take effect immediately.
Examples
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
Related Commands
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|---|---|
lapb k |
Specifies the maximum permissible number of outstanding frames, called the window size. |
lapb n1
To specify the maximum number of bits a frame can hold (the Link Access Procedure, Balanced [LAPB] N1 parameter), use the lapb n1 interface configuration command.
lapb n1 bits
Syntax Description
bits |
Maximum number of bits in multiples of eight. The minimum and maximum range is dynamically set. Use the question mark (?) to view the range. |
Defaults
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.
Command Modes
Interface configuration
Command History
Usage Guidelines
The Cisco IOS software uses the following formula to determine the minimum N1 value:
(128 (default packet size) + LAPB overhead + X.25 overhead + 2 bytes of CRC) * 8
The Cisco IOS software uses the following formula to determine for the maximum N1 value:
(hardware MTU + LAPB overhead + X.25 overhead + 2 bytes of CRC) * 8
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 accepts default packet sizes and calls that specify maximum packet sizes greater than those the LAPB layer supports, but negotiates 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 router so the call will not have a maximum packet size that exceeds the capability of either of the two interfaces involved.
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.
Examples
The following example shows how to use the question mark (?) 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.
router(config)# interface serial 1
router(config-if)# lapb n1 ?
<1080-12056> LAPB N1 parameter (bits; multiple of 8)
The following example sets the N1 bits to 16440:
router(config)# interface serial 0
router(config-if)# lapb n1 16440
router(config-if)# mtu 2048
Related Commands
lapb n2
To specify the maximum number of times a data frame can be sent (the Link Access Procedure, Balanced [LAPB] N2 parameter), use the lapb n2 interface configuration command.
lapb n2 tries
Syntax Description
tries |
Transmission count. Range: 1 to 255. |
Defaults
20 transmissions
Command Modes
Interface configuration
Command History
Examples
The following example sets the N2 tries to 50:
interface serial 0
lapb n2 50
Related Commands
lapb protocol
The lapb protocol command has been replaced by the [protocol | multi] option of the encapsulation lapb command. See the description of the [protocol | multi] option of the encapsulation lapb command earlier in this chapter for more information.
lapb t1
To set the retransmission timer period (the Link Access Procedure, Balanced [LAPB] T1 parameter), use the lapb t1 interface configuration command.
lapb t1 milliseconds
Syntax Description
milliseconds |
Time in milliseconds. Range: 1 to 64000. |
Defaults
3000 ms
Command Modes
Interface configuration
Command History
Usage Guidelines
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 ping privileged EXEC command 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.
Examples
The following example sets the T1 retransmission timer to 2000 ms:
interface serial 0
lapb t1 2000
Related Commands
lapb t2
To set the explicit acknowledge deferral timer (the Link Access Procedure, Balanced [LAPB] T2 parameter), use the lapb t2 interface configuration command.
lapb t2 milliseconds
Syntax Description
milliseconds |
Time in milliseconds. Range: 1 to 32000. Default is 0 ms (disabled) and the recommended setting. |
Defaults
0 ms (disabled), which means that the software will send an acknowledgement as quickly as possible.
Command Modes
Interface configuration
Command History
Usage Guidelines
The explicit acknowledge deferral timer determines the time that the software waits before sending an explicit acknowledgement. The acknowledgement is piggybacked with the data, unless there is no data and then an explicit acknowledgement is sent when the timer expires.
It is usually not necessary (or recommended) to set the LAPB T2 timer, but if there is a requirement, it must be set to a value smaller than that set for the LAPB T1 timer; see the ITU X.25 specifications for details.
Related Commands
lapb t4
To set the T4 idle timer, after which the Cisco IOS software 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
Syntax Description
seconds |
Number of seconds between receipt of the last frame and transmission of the outgoing poll. |
Defaults
0 seconds
Command Modes
Interface configuration
Command History
Usage Guidelines
Any non-zero T4 duration must be greater than T1, the Link Access Procedure, Balanced (LAPB) retransmission timer period.
Examples
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
Related Commands
logging event frame-relay x25
To enable notification of X.25 Annex G session status changes to be displayed on a console or system log, use the logging event frame-relay x25 command in interface configuration mode. To disable notification, use the no form of this command.
logging event frame-relay x25
no logging event frame-relay x25
Syntax Description
This command has no arguments or keywords.
Defaults
X.25 Annex G session status change notifications are not enabled.
Command Modes
Interface configuration
Command History
|
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|---|---|
12.2(2)T |
This command was introduced. |
Examples
The following example shows how to enable notification of X.25 Annex G session status changes to be displayed on a console or system log using the logging event frame-relay x25 interface configuration command:
Router(config-if)# logging event frame-relay x25
The following is an example of the Annex G status change notifications:
%X25-5-UPDOWN: Interface <interface> - DLCI <dlci number> X.25 packet layer changed state
to DOWN
%X25-5-UPDOWN: Interface <interface> - DLCI <dlci number> X25 packet layer changed state
to UP
lz entropy-check
To enable adaptive Lempel-Ziv (LZ) compression through entropy checking, use the lz entropy-check command in parameter-map configuration mode. To disable the LZ entropy checking, use the no form of this command.
lz entropy-check
no lz entropy-check
Syntax Description
This command has no arguments or keywords.
Command Default
Entropy checking is disabled.
Command Modes
Parameter-map configuration (config-profile)
Command History
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|---|---|
15.1(2)T |
This command was introduced. |
Usage Guidelines
Use this command to enable adaptive LZ compression through entropy checking.
Examples
The following example shows how to enable LZ entropy checking:
Router(config)# parameter-map type waas waas_global
Router(config-profile) lz entropy-check
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