Table Of Contents
RADIUS Tunnel Attribute Extensions
Last Updated: July 31, 2009
The RADIUS Tunnel Attribute Extensions feature introduces RADIUS attribute 90 (Tunnel-Client-Auth-ID) and RADIUS attribute 91 (Tunnel-Server-Auth-ID). Both attributes help support the provision of compulsory tunneling in virtual private networks (VPNs) by allowing the user to specify authentication names for the network access server (NAS) and the RADIUS server.
Finding Feature Information
For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for RADIUS Tunnel Attribute Extensions" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.
This feature module describes the RADIUS Tunnel Attribute Extensions feature. It includes the following sections:
To use RADIUS attributes 90 and 91, you must complete the following tasks:
•Configure your NAS to support AAA.
•Configure your NAS to support RADIUS.
•Configure your NAS to support VPN.
Your RADIUS server must support tagged attributes to use RADIUS tunnel attributes 90 and 91.
Information About RADIUS Tunnel Attribute Extensions
This section includes the following concepts:
RADIUS Tunnel Attribute Extension Benefits
The RADIUS Tunnel Attribute Extensions feature allows you to specify a name (other than the default) of the tunnel initiator and the tunnel terminator. Thus, you can establish a higher level of security when setting up VPN tunneling.
RADIUS Tunnel Attribute Extension Description
Once a NAS has set up communication with a RADIUS server, you can enable a tunneling protocol. Some applications of tunneling protocols are voluntary, but others involve compulsory tunneling; that is, a tunnel is created without any action from the user and without allowing the user any choice in the matter. In those cases, new RADIUS attributes are needed to carry the tunneling information from the NAS to the RADIUS server to establish authentication. These new RADIUS attributes are listed in Table 1.
Note In compulsory tunneling, any security measures in place apply only to traffic between the tunnel endpoints. Encryption or integrity protection of tunneled traffic must not be considered as a replacement for end-to-end security.
Table 1 RADIUS Tunnel Attributes
Number IETF RADIUS Tunnel Attribute Equivalent TACACS+ Attribute Supported Protocols Description
Layer 2 Tunneling Protocol (L2TP)
Specifies the name used by the tunnel initiator (also known as the NAS1 ) when authenticating tunnel setup with the tunnel terminator.
Layer 2 Tunneling Protocol (L2TP)
Specifies the name used by the tunnel terminator (also known as the Home Gateway2 ) when authenticating tunnel setup with the tunnel initiator.
1 When L2TP is used, the NAS is referred to as an L2TP access concentrator (LAC).
2 When L2TP is used, the Home Gateway is referred to as an L2TP network server (LNS).
RADIUS attribute 90 and RADIUS attribute 91 are included in the following situations:
•If the RADIUS server accepts the request and the desired authentication name is different from the default, they must be included it.
•If an accounting request contains Acct-Status-Type attributes with values of either start or stop and pertains to a tunneled session, they should be included in.
How to Configure RADIUS Tunnel Attribute Extensions
There are no configuration tasks associated with this feature.
Verifying RADIUS Attribute 90 and RADIUS Attribute 91
To verify that RADIUS attribute 90 and RADIUS attribute 91 are being sent in access accepts and accounting requests, use the following command in privileged EXEC mode:
Router# debug radius
Displays information associated with RADIUS. The output of this command shows whether attribute 90 and attribute 91 are being sent in access accepts and accounting requests.
This section provides the following configuration examples:
L2TP Network Server (LNS) Configuration Example
The following example shows how to configure the LNS with a basic L2F and L2TP configuration using RADIUS tunneling attributes 90 and 91:aaa new-modelaaa authentication login default noneaaa authentication login console noneaaa authentication ppp default local group radiusaaa authorization network default group radius if-authenticated!username l2tp-svr-auth-id password 0 l2tp-tnl-pass!vpdn enablevpdn search-order domain!vpdn-group 1accept-dialinprotocol l2tpvirtual-template 1terminate-from hostname l2tp-cli-auth-idlocal name l2tp-svr-auth-id!interface loopback0ip address 10.0.0.3 255.255.255.0no ip route-cacheno ip mroute-cache!interface Virtual-Template1ip unnumbered loopback0ppp authentication pap!radius-server host 184.108.40.206 auth-port 1645 acct-port 1646radius-server key <deleted>!
RADIUS User Profile with RADIUS Tunneling Attributes 90 and 91 Example
The following is an example of a RADIUS user profile that includes RADIUS tunneling attributes 90 and 91 for an L2TP tunnel.cisco.com Password = "cisco", Service-Type = OutboundService-Type = Outbound,Tunnel-Type = :1:L2TP,Tunnel-Medium-Type = :1:IP,Tunnel-Client-Endpoint = :1:"10.0.0.2",Tunnel-Server-Endpoint = :1:"10.0.0.3",Tunnel-Client-Auth-Id = :1:"l2tp-cli-auth-id",Tunnel-Server-Auth-Id = :1:"l2tp-svr-auth-id",Tunnel-Assignment-Id = :1:"l2tp-assignment-id",Cisco-Avpair = "vpdn:l2tp-tunnel-password=l2tp-tnl-pass",Tunnel-Preference = :1:1
The following sections provide references related to the RADIUS Tunnel Attribute Extensions feature.
Related Topic Document Title
Overview of RADIUS attributes
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
Feature Information for RADIUS Tunnel Attribute Extensions
Table 2 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.
Note Table 2 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE software release train also support that feature.
Layer 2 Tunnel Protocol (L2TP)—A Layer 2 tunneling protocol that enables an ISP or other access service to create a virtual tunnel to link customer remote sites or remote users with corporate home networks. In particular, a network access server (NAS) at the ISP point of presence (POP) exchanges PPP messages with the remote users and communicates by L2F or L2TP requests and responses with the customer tunnel server to set up tunnels.
L2TP access concentrator (LAC)—A network access server (NAS) to which the client directly connects and through which PPP frames are tunneled to the L2TP network server (LNS). The LAC need only implement the media over which L2TP is to operate to pass traffic to one or more LNSs. The LAC may tunnel any protocol carried within PPP. The LAC initiates incoming calls and receives outgoing calls. A LAC is analogous to an L2F network access server.
L2TP network server (LNS)—A termination point for L2TP tunnels, and an access point where PPP frames are processed and passed to higher-layer protocols. An LNS can operate on any platform that terminates PPP. The LNS handles the server side of the L2TP protocol. L2TP relies only on the single medium over which L2TP tunnels arrive. The LNS initiates outgoing calls and receives incoming calls. An LNS is analogous to a home gateway in L2F technology.
network access server (NAS)—A Cisco platform, or collection of platforms, such as an AccessPath system, that interfaces between the packet world (such as the Internet) and the circuit-switched world (such as the PSTN).
tunnel—A virtual pipe between the L2TP access concentrator (LAC) and L2TP network server (LNS) that can carry multiple PPP sessions.
virtual private network (VPN)—A system that permits dial-in networks to exist remotely to home networks, while giving the appearance of being directly connected. VPNs use L2TP and L2F to terminate the Layer 2 and higher parts of the network connection at the L2TP network server (LNS) instead of the L2TP access concentrator (LAC).
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