RADIUS Vendor-Specific Attributes and RADIUS Disconnect-Cause Attribute Values

The Internet Engineering Task Force (IETF) draft standard specifies a method for communicating vendor-specific information between the network access server and the RADIUS server by using the vendor-specific attribute (attribute 26). Attribute 26 encapsulates vendor specific attributes, thereby, allowing vendors to support their own extended attributes otherwise not suitable for general use.

Information About RADIUS Vendor-Specific Attributes and RADIUS Disconnect-Cause Attribute Values

The Cisco RADIUS implementation supports one vendor-specific option using the format recommended in the specification. Cisco’s vendor-ID is 9, and the supported option has vendor-type 1, which is named “cisco-avpair.” The value is a string of the following format: 


protocol : attribute sep value *

“Protocol” is a value of the Cisco “protocol” attribute for a particular type of authorization; protocols that can be used include IP, IPX, VPDN, VOIP, SHELL, RSVP, SIP, AIRNET, OUTBOUND. “Attribute” and “value” are an appropriate attribute-value (AV) pair defined in the Cisco TACACS+ specification, and “sep” is “=” for mandatory attributes and “*” for optional attributes. This allows the full set of features available for TACACS+ authorization to also be used for RADIUS.

For example, the following AV pair causes Cisco’s “multiple named ip address pools” feature to be activated during IP authorization (during PPP’s IPCP address assignment): 


cisco-avpair= ”ip:addr-pool=first“

If you insert an “*”, the AV pair “ip:addr-pool=first” becomes optional. Note that any AV pair can be made optional. 


cisco-avpair= ”ip:addr-pool*first“

The following example shows how to cause a user logging in from a network access server to have immediate access to EXEC commands: 


cisco-avpair= ”shell:priv-lvl=15“

Attribute 26 contains the following three elements:

  • Type

  • Length

  • String (also known as data)
    • Vendor-Id
    • Vendor-Type
    • Vendor-Length
    • Vendor-Data

The figure below shows the packet format for a VSA encapsulated “behind” attribute 26.

Figure 1. VSA Encapsulated Behind Attribute 26

Note

It is up to the vendor to specify the format of their VSA. The Attribute-Specific field (also known as Vendor-Data) is dependent on the vendor's definition of that attribute.

The table below describes significant fields listed in the Vendor-Specific RADIUS IETF Attributes table (second table below), which lists supported vendor-specific RADIUS attributes (IETF attribute 26).

Table 1. Vendor-Specific Attributes Table Field Descriptions

Field

Description

Number

All attributes listed in the following table are extensions of IETF attribute 26.

Vendor-Specific Command Codes

A defined code used to identify a particular vendor. Code 9 defines Cisco VSAs, 311 defines Microsoft VSAs, and 529 defines Ascend VSAs.

Sub-Type Number

The attribute ID number. This number is much like the ID numbers of IETF attributes, except it is a “second layer” ID number encapsulated behind attribute 26.

Attribute

The ASCII string name of the attribute.

Description

Description of the attribute.

Table 2. Vendor-Specific RADIUS IETF Attributes

Number

Vendor-Specific Company Code

Sub-Type Number

Attribute

Description

MS-CHAP Attributes

26

311

1

MSCHAP-Response

Contains the response value provided by a PPP MS-CHAP user in response to the challenge. It is only used in Access-Request packets. This attribute is identical to the PPP CHAP Identifier. (RFC 2548 )

26

311

11

MSCHAP-Challenge

Contains the challenge sent by a network access server to an MS-CHAP user. It can be used in both Access-Request and Access-Challenge packets. (RFC 2548 )

VPDN Attributes

26

9

1

l2tp-busy-disconnect

If a vpdn-group on an LNS uses a virtual-template that is configured to be pre-cloned, this attribute will control the disposition of a new L2TP session that finds no pre-cloned interface to which to connect. If the attribute is true (the default), the session will be disconnected by the LNS. Otherwise, a new interface will be cloned from the virtual-template.

26

9

1

l2tp-cm-local-window-size

Specifies the maximum receive window size for L2TP control messages. This value is advertised to the peer during tunnel establishment.

26

9

1

l2tp-drop-out-of-order

Respects sequence numbers on data packets by dropping those that are received out of order. This does not ensure that sequence numbers will be sent on data packets, just how to handle them if they are received.

26

9

1

l2tp-hello-interval

Specifies the number of seconds for the hello keepalive interval. Hello packets are sent when no data has been sent on a tunnel for the number of seconds configured here.

26

9

1

l2tp-hidden-avp

When enabled, sensitive AVPs in L2TP control messages are scrambled or hidden.

26

9

1

l2tp-nosession-timeout

Specifies the number of seconds that a tunnel will stay active with no sessions before timing out and shutting down.

26

9

1

tunnel-tos-reflect

Copies the IP ToS field from the IP header of each payload packet to the IP header of the tunnel packet for packets entering the tunnel at the LNS.

26

9

1

l2tp-tunnel-authen

If this attribute is set, it performs L2TP tunnel authentication.

26

9

1

l2tp-tunnel-password

Shared secret used for L2TP tunnel authentication and AVP hiding.

26

9

1

l2tp-udp-checksum

This is an authorization attribute and defines whether L2TP should perform UDP checksums for data packets. Valid values are “yes” and “no.” The default is no.

H323 Attributes

26

9

23

Remote-Gateway-ID

(h323-remote-address)

Indicates the IP address of the remote gateway.

26

9

24

Connection-ID

(h323-conf-id)

Identifies the conference ID.

26

9

25

Setup-Time

(h323-setup-time)

Indicates the setup time for this connection in Coordinated Universal Time (UTC) formerly known as Greenwich Mean Time (GMT) and Zulu time.

26

9

26

Call-Origin

(h323-call-origin)

Indicates the origin of the call relative to the gateway. Possible values are originating and terminating (answer).

26

9

27

Call-Type

(h323-call-type)

Indicates call leg type. Possible values are telephony and VoIP .

26

9

28

Connect-Time

(h323-connect-time)

Indicates the connection time for this call leg in UTC.

26

9

29

Disconnect-Time

(h323-disconnect-time)

Indicates the time this call leg was disconnected in UTC.

26

9

30

Disconnect-Cause

(h323-disconnect-caus)e

Specifies the reason a connection was taken offline per Q.931 specification.

26

9

31

Voice-Quality

(h323-voice-quality)

Specifies the impairment factor (ICPIF) affecting voice quality for a call.

26

9

33

Gateway-ID

(h323-gw-id)

Indicates the name of the underlying gateway.

Large Scale Dialout Attributes

26

9

1

callback-dialstring

Defines a dialing string to be used for callback.

26

9

1

data-service

No description available.

26

9

1

dial-number

Defines the number to dial.

26

9

1

force-56

Determines whether the network access server uses only the 56 K portion of a channel, even when all 64 K appear to be available.

26

9

1

map-class

Allows the user profile to reference information configured in a map class of the same name on the network access server that dials out.

26

9

1

send-auth

Defines the protocol to use (PAP or CHAP) for username-password authentication following CLID authentication.

Miscellaneous Attributes

26

9

2

Cisco-NAS-Port

Specifies additional vendor specific attribute (VSA) information for NAS-Port accounting. To specify additional NAS-Port information in the form an Attribute-Value Pair (AVPair) string, use the radius-server vsa send global configuration command.

Note

 

This VSA is typically used in Accounting, but may also be used in Authentication (Access-Request) packets.

26

9

1

min-links

Sets the minimum number of links for MLP.

26

9

1

proxyacl#<n>

Allows users to configure the downloadable user profiles (dynamic ACLs) by using the authentication proxy feature so that users can have the configured authorization to permit traffic going through the configured interfaces.

26

9

1

spi

Carries the authentication information needed by the home agent to authenticate a mobile node during registration. The information is in the same syntax as the ip mobile secure host <addr> configuration command. Basically it contains the rest of the configuration command that follows that string, verbatim. It provides the Security Parameter Index (SPI), key, authentication algorithm, authentication mode, and replay protection timestamp range.

26

9

1

client-mac-address

Contains the MAC address of the PPPoE client.

Note

 

This attribute is applicable only to PPP over Ethernet (PPPoE) or to PPP over ATM (PPPoA).

See “Configuring Router to Use Vendor-Specific RADIUS Attributes” section of t he Configuring RADIUS feature module for more information on configuring your NAS to recognize and use VSAs.

RADIUS Disconnect-Cause Attribute Values

Disconnect-cause attribute values specify the reason a connection was taken offline. The attribute values are sent in Accounting request packets. These values are sent at the end of a session, even if the session fails to be authenticated. If the session is not authenticated, the attribute can cause stop records to be generated without first generating start records.

The table below lists the cause codes, values, and descriptions for the Disconnect-Cause (195) attribute.


Note

The Disconnect-Cause is incremented by 1000 when it is used in RADIUS AVPairs; for example, disc-cause 4 becomes 1004.

Table 3. Disconnect-Cause Attribute Values

Cause Code

Value

Description

2

Unknown

Reason unknown.

4

CLID-Authentication-Failure

Failure to authenticate number of the calling-party.

10

No-Carrier

No carrier detected.

Note

 

Codes 10, 11, and 12 can be sent if there is a disconnection during initial modem connection.

11

Lost-Carrier

Loss of carrier.

12

No-Detected-Result-Codes

Failure to detect modem result codes.

20

User-Ends-Session

User terminates a session.

Note

 

Codes 20, 22, 23, 24, 25, 26, 27, and 28 apply to EXEC sessions.

21

Idle-Timeout

Timeout waiting for user input.

Codes 21, 100, 101, 102, and 120 apply to all session types.

22

Exit-Telnet-Session

Disconnect due to exiting Telnet session.

23

No-Remote-IP-Addr

Could not switch to SLIP/PPP; the remote end has no IP address.

24

Exit-Raw-TCP

Disconnect due to exiting raw TCP.

25

Password-Fail

Bad passwords.

26

Raw-TCP-Disabled

Raw TCP disabled.

27

Control-C-Detected

Control-C detected.

28

EXEC-Process-Destroyed

EXEC process destroyed.

40

Timeout-PPP-LCP

PPP LCP negotiation timed out.

Note

 

Codes 40, 41, 42, 43, 44, 45, and 46 apply to PPP sessions.

41

Failed-PPP-LCP-Negotiation

PPP LCP negotiation failed.

42

Failed-PPP-PAP-Auth-Fail

PPP PAP authentication failed.

43

Failed-PPP-CHAP-Auth

PPP CHAP authentication failed.

44

Failed-PPP-Remote-Auth

PPP remote authentication failed.

45

PPP-Remote-Terminate

PPP received a Terminate Request from remote end.

46

PPP-Closed-Event

Upper layer requested that the session be closed.

63

PPP-Echo-Replies

TCP connection has been closed.

100

Session-Timeout

Session timed out.

101

Session-Failed-Security

Session failed for security reasons.

102

Session-End-Callback

Session terminated due to callback.

120

Invalid-Protocol

Call refused because the detected protocol is disabled.

600

VPN-User-Disconnect

Call disconnected by client (through PPP).

Code is sent if the LNS receives a PPP terminate request from the client.

601

VPN-Carrier-Loss

Loss of carrier. This can be the result of a physical line going dead.

Code is sent when a client is unable to dial out using a dialer.

602

VPN-No-Resources

No resources available to handle the call.

Code is sent when the client is unable to allocate memory (running low on memory).

603

VPN-Bad-Control-Packet

Bad L2TP or L2F control packets.

This code is sent when an invalid control packet, such as missing mandatory Attribute-Value pairs (AVP), from the peer is received. When using L2TP, the code will be sent after six retransmits; when using L2F, the number of retransmits is user configurable.

Note

 

VPN-Tunnel-Shut will be sent if there are active sessions in the tunnel.

604

VPN-Admin-Disconnect

Administrative disconnect. This can be the result of a VPN soft shutdown, which is when a client reaches maximum session limit or exceeds maximum hopcount.

Code is sent when a tunnel is brought down by issuing the clear vpdn tunnel command.

605

VPN-Tunnel-Shut

Tunnel teardown or tunnel setup has failed.

Code is sent when there are active sessions in a tunnel and the tunnel goes down.

Note

 

This code is not sent when tunnel authentication fails.

606

VPN-Local-Disconnect

Call is disconnected by LNS PPP module.

Code is sent when the LNS sends a PPP terminate request to the client. It indicates a normal PPP disconnection initiated by the LNS.

607

VPN-Session-Limit

VPN soft shutdown is enabled.

Code is sent when a call has been refused due to any of the soft shutdown restrictions previously mentioned.

611

VPDN-Tunnel-In-Resync

VPDN tunnel is in HA resync.

Additional References

The following sections provide references related to RADIUS Vendor-Specific Attributes (VSA) and RADIUS Disconnect-Cause Attribute Values.

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Security commands

Cisco IOS Security Command Reference

Security Features

Cisco IOS XE Security Configuration Guide: Securing User Services , Release 2

Security Server Protocols

Security Server Protocols section of the Cisco IOS XE Security Configuration Guide: Securing User Services , Release 2

RADIUS Configuration

Configuring RADIUS feature module.

Standards

Standard

Title

Internet Engineering Task Force (IETF) Internet Draft: Network Access Servers Requirements

Network Access Servers Requirements: Extended RADIUS Practices

MIBs

MIB

MIBs Link

None.

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

RFC 2865

Remote Authentication Dial In User Service (RADIUS)

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for RADIUS Vendor-Specific Attributes and RADIUS Disconnect-Cause Attribute Values

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 4. Feature Information for RADIUS Vendor-Specific Attributes (VSA) and RADIUS Disconnect-Cause Attribute Values

Feature Name

Releases

Feature Information

Accounting of VPDN Disconnect Cause

Cisco IOS XE Release 2.1

This feature was introduced on Cisco ASR 1000 Series Routers.

Vendor-Specific RADIUS Attributes

Cisco IOS XE Release 2.1

This document discusses the Internet Engineering Task Force (IETF) draft standard, which specifies a method for communicating vendor-specific information between the network access server and the RADIUS server by using the vendor-specific attribute (attribute 26). Attribute 26 encapsulates vendor specific attributes, thereby, allowing vendors to support their own extended attributes otherwise not suitable for general use.

In Cisco IOS XE Release 2.1, this feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers.