# LAC Service Configuration Mode Commands

The LAC Service Configuration Mode is used to create and manage L2TP services within contexts on the system. L2TP Access Concentrator (LAC) services facilitate tunneling to peer L2TP Network Servers (LNSs).

IMPORTANT:

The commands or keywords/variables that are available are dependent on platform type, product version, and installed license(s).
allow

This command configure the system to allow different attributes in the LAC Hostname Attribute Value Pair (AVP) and Called-Number AVP for L2TP messages exchanged between LAC and LNS.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    allow { aaa-assigned-hostname | called-number value
    apn }

    [ default | no ] allow { aaa-assigned-hostname | called-number
    value apn }

no

Disable the configured attribute and returns to the behavior that uses the LAC-Service name as the HostName AVP.
aaa-assigned-hostname

When enabled if AAA assigns a valid Tunnel-Client-Auth-ID attribute for the tunnel, it is used as the HostName AVP in the L2TP tunnel setup message.

This keyword works in conjunction with the local-hostname hostname keyword applied via the tunnel l2tp command in APN Configuration mode.

When Tunnel parameters are not received from the RADIUS Server, Tunnel parameters configured in an APN are considered for the LNS peer selection. When APN configuration is selected, the local-hostname configured with the tunnel l2tp command in the APN for the LNS peer will be used as an LAC Hostname.
called-number value apn

Configures the system to send the APN name in the Called-Number AVP as a part of ICRQ message sent to the LNS. If this keyword is not configured, Called-Number AVP will not be included in ICRQ message sent to the LNS.
Usage:

Use this command to configure the attribute for the HostName AVP for L2TP messages exchanged between LAC and LNS.

LAC Hostname will be different for the subscribers corresponding to the different corporate APNs. In the absence of a AAA assigned HostName, the LAC-Service name is used as HostName. By default the LAC-Service name is used as the HostName AVP.
Example:
The following command enables the use of the value of Tunnel-Client-Auth-ID attribute for the HostName AVP:

    allow aaa-assigned-hostname

Use the following command to reset the behavior so that the LAC-Service uses the LAC-Service name as the HostName AVP:

    no allow aaa-assigned-hostname

bind

This command assigns a local end point address to the LAC service in the current context.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    bind ip_address [ max-subscribers ]

    no bind ip_address

no

Unassign, or unbind, the local end point to the LAC service.
ip_address

This must be a valid IP address entered using IPv4 dotted-decimal notation.
max-subscribers

The maximum number of subscribers that can use the endpoint for this LAC service. Must be an integer from 1 to 2500000.
Usage:

Use this command to bind a local end point IP address to the LAC service.
Example:
The following command binds the local end point IP address 10.10.10.100 to the LAC service in the current context:

    bind 10.10.10.100

The following command removes the binding of the local end point to the LAC service:

    no bind

data sequence-number

Enables data sequence numbering for sessions that use the current LAC service. Data sequence numbering is enabled by default.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    [ no ] data
    sequence-number

no

Disables data sequence numbering for sessions.
Usage:

An L2TP data packet header has an optional data sequence numbers field. The data sequence number may be used to ensure ordered delivery of data packets. This command is used to re-enable or disable the use of the data sequence numbers for data packets.
Example:
Use the following command to disable the use of data sequence numbering:

    no data sequence-number

Use the following command to re-enable data sequence numbering:

    data sequence-number

default

This command sets the specified LAC service parameter to its default value or setting.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    default { data
    sequence-number | hide-attributes | keepalive-interval | load-balancing | local-receive-window | max-retransmission | max-session-per-tunnel | max-tunnel-challenge-length | max-tunnels | proxy-lcp-authentication | retransmission-timeout-first | retransmission-timeout-max | trap
    all | tunnel-authentication }

data sequence-number

Enables data sequence numbering for sessions.
hide-attributes

Disables hiding attributes in control messages sent from the LAC to the LNS.
keepalive-interval

Sets the interval for send L2TP Hello keepalive if there is no control or data transactions to the default value of 60 seconds.
load-balancing

Sets the load balancing algorithm to be used when many LNS peers have been configured to the default of round robin.
local-receive-window

Sets the window size to be used for the local side for the reliable control transport to the default of 16.
max-retransmission

Sets the maximum number of retransmissions to the default of 5.
max-session-per-tunnel

Sets the maximum number of sessions per tunnel at any point in time to the default of 512.
max-tunnel-challenge-length

Sets the maximum length of the tunnel challenge to the default of 16 bytes.
max-tunnels

Sets the maximum number of tunnels for this service to the default of 32000.
proxy-lcp-authentication

Sets sending of proxy LCP authentication parameters to the LNS to the default state of enabled.
retransmission-timeout-first

Sets the first retransmit interval to the default of 1 second.
retransmission-timeout-max

Sets the maximum retransmit interval to the default of 8 seconds.
trap all

Generates all supported SNMP traps.
tunnel-authentication

Sets tunnel authentication to the default state of enabled.
Usage:

Use the default command to set LAC service parameters to their default states.
Example:
Use the following command to set the keep alive interval to the default value of 60 seconds:

    default

    keepalive-interval

Use the following command to set the maximum number of sessions per tunnel to the default value of 512:

    default max-session-per-tunnel

end

Exits the current configuration mode and returns to the Exec mode.
Product:

All
Privilege:

Security Administrator, Administrator
Syntax

    end

Usage:

Use this command to return to the Exec mode.
exit

Exits the current mode and returns to the parent configuration mode.
Product:

All
Privilege:

Security Administrator, Administrator
Syntax

    exit

Usage:

Use this command to return to the parent configuration mode.
hide-attributes

Enables hiding certain attributes (such as proxy-auth-name and proxy-auth-rsp) in control messages sent from the LAC to the LNS. The LAC hides such attributes only if tunnel authentication is enabled between the LAC and the LNS.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    [ no ] hide-attributes

no

Disable hiding attributes.
Usage:

Use this command to hide certain attributes from control messages when tunnel authentication is enabled between the LAC and the LNS.
Example:
The following command enables hiding attributes:

    hide-attributes

keepalive-interval

This command specifies the amount of time to wait before sending a Hello keep alive message.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    keepalive-interval seconds

    no keepalive-interval

no

Disables the generation of Hello keepalive messages on the tunnel.
seconds

Default: 60

The number of seconds to wait before sending a Hello keepalive message. The number can be configured to an integer from 30 to 2147483648.
Usage:

Use this command to set the amount of time to wait before sending a Hello keepalive message or disable the generation of Hello keep alive messages completely. A keepalive mechanism is employed by L2TP in order to differentiate tunnel outages from extended periods of no control or data activity on a tunnel. This is accomplished by injecting Hello control messages after a specified period of time has elapsed since the last data or control message was received on a tunnel. As for any other control message, if the Hello message is not reliably delivered then the tunnel is declared down and is reset. The transport reset mechanism along with the injection of Hello messages ensures that a connectivity failure between the LNS and the LAC is detected at both ends of a tunnel.
Example:
Use the following command to set the Hello keepalive message interval to 120 seconds:

    keepalive-interval 120

Use the following command to disable the generation of Hello keepalive messages:

    no keepalive-interval

load-balancing

Configures how LNSs are selected for this LAC service.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    load-balancing { balanced | prioritized | random }

balanced

LNS selection is made without regard to prioritization, but in a sequential order that balances the load across the total number of LNS nodes available.
prioritized

LNS selection is made based on the priority assigned in the Tunnel-Preference attribute. An example of this method is three LNS nodes, with preferences of 1, 2, and 3 respectively. In this example, the RADIUS server always tries the tunnel with a preference of 1 before using any of the other LNS nodes.
random

Default: Enabled

LNS selection is random in order, wherein the RADIUS server does not use the Tunnel-Preference attribute in determining which LNS to select.
Usage:

Use this command to configure the load-balancing algorithm that defines how the LNS node is selected by the LAC when there are multiple peer LNSs configured in the LAC service.
Example:
The following command sets the LAC service to connect to LNSs in a sequential order;

    load-balancing balanced

The following command sets the LAC service to connect to LNSs according to the priority assigned through the Tunnel-Preference attribute:

    load-balancing prioritized

local-receive-window

Specifies the number of control messages the remote peer LNS can send before waiting for an acknowledgement.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    local-receive-window integer

integer

Default: 4

Specifies the number of control messages to send before waiting for an acknowledgement. The number can be configured to an integer from 1 to 256.
Usage:

Use this command to set the size of the control message receive window being offered to the remote peer LNS. The remote peer LNS may send the specified number of control messages before it must wait for an acknowledgment.
Example:
The following command sets the local receive window to 10 control messages:

    local-receive-window 10

max-retransmission

Sets the maximum number of retransmissions of a control message to a peer before the tunnel and all sessions within it are cleared.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    max-retransmission integer

integer

Default: 5

Specifies the maximum number of retransmissions of a control message to a peer. This value must be an integer from1 through 10.
Usage:

Each tunnel maintains a queue of control messages to be transmitted to its peer. After a period of time passes without acknowledgement, a message is retransmitted. Each subsequent retransmission of a message employs an exponential backoff interval. For example; if the first retransmission occurs after 1 second, the next retransmission occurs after 2 seconds has elapsed, then the next after 4 seconds. If no peer response is detected after the number of retransmissions set by this command, the tunnel and all sessions within are cleared.

Use this command to set the maximum number of retransmissions that the LAC service sends before closing the tunnel and all sessions within. it.
Example:
The following command sets the maximum number of retransmissions of a control message to a peer to 7:

    max-retransmissions 7

max-session-per-tunnel

Sets the maximum number of sessions that can be facilitated by a single a tunnel at any time.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    max-sessions-per-tunnel integer

integer

Default: 512

The maximum number of sessions expressed as an integer from 1 through 65535.
Usage:

Use this command to set the maximum number of sessions you want to allow in a tunnel.
Example:
The following command sets the maximum number of sessions in a tunnel to 5000:

    max-sessions-per-tunnel 5000

max-tunnel-challenge-length

Sets the maximum length of the tunnel challenge in bytes.The challenge is used for tunnel authentication purposes during tunnel creation.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    max-tunnel-challenge-length bytes

bytes

Default: 16

Specifies the maximum length (in bytes of the tunnel challenge. This must be an integer from 4 through 32.
Usage:

Use this command to set the maximum length (in bytes) for the tunnel challenge that is used during tunnel creation.
Example:
The following command sets the maximum length of the tunnel challenge to 32 bytes:

    max-tunnel-challenge-length
    32

max-tunnels

The maximum number of tunnels that the current LAC service can support.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    max-tunnels integer

integer

Default: 32000

The maximum number of tunnels expressed as an integer from 1 through 32000.
Usage:

Use this command to set the maximum number tunnels that this LAC service can support at any on time.
Example:

Use the following command to set the maximum number of tunnels for the current LAC service to 20000:

    max-tunnels 20000

peer-lns

Adds a peer LNS address for the current LAC service. Up to eight peer LNSs can be configured for each LAC service.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    peer-lns ip_address [ encrypted ] secret secret [ crypto-map map_name { [ encrypted ] isakmp-secret secret } ] [ description text ] [ preference integer ]

    no peer-lns ip_address

no peer-lns ip_address

Deletes the peer LNS at the IP address specified by ip_address. ip_address must be entered in IPv4 dotted-decimal notation.
ip_address

The IP address of the peer LNS for the current LAC service. ip_address must be entered in IPv4 dotted-decimal notation.
[ encrypted ] secret secret

Designates the secret which is shared between the current LAC service and the peer LNS. secret must be an alphanumeric string of 1 through 256 characters that is case sensitive.

encrypted secret secret: Specifies that encryption should be used when communicating the secret with the peer LNS.
crypto-map map_name { [ encrypted ] isakmp-secret secret }

map_name is the name of a crypto map that has been configured in the current context. map_name must be an alphanumeric string of 1 through 127 characters that is case sensitive.

isakmp-secret secret: The pre-shared key for IKE. secret must be an alphanumeric string of 1 through 127 characters that is case sensitive.

encrypted isakmp-secret secret: The pre-shared key for IKE. Encryption must be used when sending the key. secret must be an alphanumeric string of 1 through 127 characters.
description text

Specifies the descriptive text to use to describe the specified peer LNS. text must be an alphanumeric string of 0 through 79 characters.
preference integer

This sets the priority of the peer LNS if multiple peer LNSs are configured. integer must be an integer from 1 through 128.
Usage:

Use this command to add a peer LNS address for the current LAC service.
Example:
The following command adds a peer LNS to the current LAC service with the IP address of 10.10.10.100, sets encryption on, specifies the shared secret to be 1b34nnf5d, and sets the preference to 3:

    peer-lns 10.10.10.100
    encrypted secret 1b34nnf5d preference 3

The following command removes the peer LNS with the IP address of 10.10.10.200 for the current LAC service:

    no peer-lns 10.10.10.200

proxy-lcp-authentication

Enables and disables the sending of proxy LCP authentication parameters to the LNS.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    [ no ] proxy-lcp-authentication

no

Disables the sending of proxy LCP authentication parameters to the LNS.
proxy-lcp-authentication

Default: Enabled

Enables the sending of proxy LCP authentication parameters to the LNS.
Usage:

Use this feature in situations where the peer LNS does not understand the proxy LCP Auth AVPs that the system sends and does not do an LCP renegotiation and tears down the call.
Example:
Use the following command to disable the sending of proxy LCP authentication parameters to the LNS;

    no proxy-lcp-authentication

Use the following command to re-enable the sending of proxy LCP authentication parameters to the LNS:

    proxy-lcp-authentication

retransmission-timeout-first

Each tunnel maintains a queue of control messages to transmit to its peer. After a period of time passes without acknowledgement, a message is retransmitted. This command sets the initial timeout for retransmission of control messages.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    retransmission-timeout-first integer

integer

Default: 1

The amount of time to wait (in seconds) before sending the first control message retransmission. This must be an integer from 1 through 100.
Usage:

Use this command to set the initial timeout before retransmitting control messages to the peer.
Example:
The following command sets the initial retransmission timeout to 3 seconds:

    retransmission-timeout-first 3

retransmission-timeout-max

Configures maximum amount of time between two retransmission of control messages.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    retransmission-timeout-max integer

integer

Default: 8

integer is the maximum time (in seconds) to wait before retransmitting control messages expressed as e an integer from 1 through 100.
Usage:

Use this command to set the maximum amount of time that can elapse before retransmitting control messages.

Each tunnel maintains a queue of control messages to transmit to its peer. After a period of time passes without acknowledgement, a message is retransmitted. Each subsequent retransmission of a message employs an exponential backoff interval.
Example:
The following command sets the maximum retransmission time-out to 10 seconds:

    retransmission-timeout-max 10

single-port-mode

This command enables/disables the L2TP LAC service always to use standard L2TP port 1701 as source port for all L2TP control and data packets originated from LAC node.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    [ default | no ] single-port-mode

default

Default: Enabled

Sets this command to its default state of disabled. By default single source port configuration for L2TP LAC packets is disabled.
no

Disables the configured single source port configuration from this LAC service.
Usage:

Use this command to enable or disable the single port mode for L2TP LAC service.

If this feature is enabled, then L2TP LAC service will always use standard L2TP port 1701 as source port for all L2TP control/data packets originated from LAC (instead of the default scheme in which each L2TPMgr uses a dynamic source port). L2TPMgr instance 1 will handle all L2TP calls for the service.

CAUTION:

Changing this configuration, while the service is already running, will cause restart of the service.
Example:

The following command enables the LAC service to use port 1701 as source port for all L2TP control and data packets:

    single-port-mode

snoop framed-ip-address

When enabled, this feature allows the LAC to detect IP Control Protocol (IPCP) packets exchanged between the mobile node and the LNS and extract the framed-ip-address assigned to the mobile node. The address will be reported in accounting start/stop messages and displayed for subscriber sessions.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    [ default | no ] snoop
    framed-ip-address

default

Disabled.
no

Disables the feature. Accounting start/stop will occur before the PPP session is established and the framed IP address field will be reported as 0.0.0.0.
Usage:

This feature is available to address simple IP roaming scenarios. If this feature is enabled, the Accounting Start will be sent only after the framed-ip-address is detected. If the framed-ip-address is not detected within 16 seconds, an Accounting Start will be sent for the session with the 0.0.0.0 address. If the session is disconnected during the detection attempt, Accounting Start/Stop will be sent for the session. If the session renegotiates IPCP, an Accounting Stop will be generated with a framed-ip-address from the old session, and an Accounting Start will be generated with an IP address for the new session. IPv6 address detection is not supported.

IMPORTANT:

When this feature is enabled and the show subscribers all command is invoked, the framed-IP-address is displayed for the PDSN Simple IP subscriber in the output display.
trap

This command generates SNMP traps.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    [ no ] trap all

no

Disables SNMP traps.
Usage:

Use this command to enable/disable all supported SNMP traps.
Example:
To enable all supported SNMP traps, enter the following command:

    trap all

tunnel selection-key

Enables the creation of tunnels between an L2TP service and an LNS server on the basis of a key received from AAA server.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    tunnel selection-key
     { none | tunnel-client-auth-id | tunnel-server-auth-id }

    default tunnel selection-key

default

Disables the creation of tunnel between LAC service and LNS based on a key value received from AAA server.
none

Default: Enabled

This keyword disables the creation of multiple tunnels between a pair of LAC service and LNS server. LAC will not make use of the key to choose a tunnel with LNS in this setup.
tunnel-client-auth-id

Default: Disabled

This keyword enables the creation of tunnels between LAC service and an LNS server on the basis of domain attribute “Tunnel-Client-Auth-ID” value received from AAA server.
tunnel-server-auth-id

Default: Disabled

This keyword enables the creation of tunnels between LAC service and an LNS server on the basis of domain attribute “Tunnel-Server-Auth-ID” value received from AAA server.
Usage:

Use this command to enable or disable the creation of additional L2TP tunnels between LAC service and LNS server on the basis of “Tunnel-Client-Auth-ID” or “Tunnel-Server-Auth-ID” attribute value received from AAA Server in Access-Accept message. This value of attribute is treated as a key for tunnel selection and creation.

When the LAC needs to establish a new L2TP session, it first checks for an existing L2TP tunnel with the peer LNS based on the value of the key configured. If no such tunnel exists for the key, it will create a new tunnel with the LNS.

The default configuration has the selection-key as none. Hence, LAC will not make use of key to choose a tunnel with LNS in default setup.

The maximum number of sessions, as configured via the max-sessions-per-tunnel command, is applicable for each tunnel created through this command. By default, each tunnel supports 512 sessions.

If the LAC service needs to establish a new tunnel for a new L2TP session with LNS and the tunnel create request fails because maximum tunnel creation limit is reached, LAC will try other LNS addresses received from AAA server in Access-Accept message for the APN/subscriber. If all available peer-LNS are exhausted, LAC service will reject the call.
Example:
The following command enables the use of “Tunnel-Server-Auth-ID” attribute value received from AAA Server in Access-Accept message as a key for tunnel selection and creation:

    tunnel selection-key
    tunnel-server-auth-id

tunnel-authentication

Enables tunnel authentication. When tunnel authentication is enabled, a configured shared secret is used to ensure that the LAC service is communicating with an authorized peer LNS. The shared secret is configured by the peer-lns command in the LAC Service Configuration mode, the tunnel l2tp command in the Subscriber Configuration mode, or the Tunnel-Password attribute in the subscribers RADIUS profile.
Platform:

ASR 5000

ASR 5500
Product:

GGSN, PDSN, P-GW, SAEGW
Privilege:

Security Administrator, Administrator
Syntax

    [ no ] tunnel-authentication

no

Disables tunnel authentication.

Tunnel authentication is enabled by default.
Usage:

Disable or enable the usage of secrets to authenticate a peer LNS when setting up a tunnel.
Example:
To disable tunnel authentication, use the following command:

    no tunnel-authentication

To re-enable tunnel authentication, use the following command:

    tunnel-authentication