The IETF 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). Vendor-specific attributes (VSAs) allow vendors to
support their own extended attributes not suitable for general use. 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 with this 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, Internetwork Packet Exchange (IPX), VPDN, VoIP, Secure Shell (SSH), Resource Reservation Protocol (RSVP), Serial
Interface Processor (SIP), AirNet, and Outbound. “Attribute” and “value” are an appropriate AV pair defined in the Cisco TACACS+
specification, and “sep” is “=” for mandatory attributes and “*” for optional attributes, allowing 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 Internet Protocol Control Protocol (IPCP) address assignment):
If you insert an “*”, the AV pair “ip:addr-pool=first” becomes optional. Note that any AV pair can be made optional:
The following example shows how to cause a user logging in from a network access server to have immediate access to EXEC
Other vendors have their own unique vendor IDs, options, and associated VSAs.