Cisco IOS and Radius

0.  INTRODUCTION

Cisco NAS equipment has become quite popular of late, but being Cisco
equipment running IOS, the configuration can be a bit non-obvious to the
unfamiliar.  This document aims to describe the most common configuration
options to make your Ciscos interoperate with radius as you would expect a
well-behaved NAS to do.

1.  IOS 12.x

For Cisco 12.x ( 12.0 and 12.1 ), the following AAA configuration directives
are suggested:

    aaa new-model
    aaa authentication login default group radius local
    aaa authentication login localauth local
    aaa authentication ppp default if-needed group radius local
    aaa authorization exec default group radius local
    aaa authorization network default group radius local
    aaa accounting delay-start
    aaa accounting exec default start-stop group radius
    aaa accounting network default start-stop group radius
    aaa processes 6

this configuration works very well with most radius servers.  One of the more
important configurations is:

    aaa accounting delay-start

This directive will delay the sending of the Accounting Start packet until
after an IP address has been assigned during the PPP negotiation process.
This will supersede the need to enable the sending of "Alive" packets as
described below for IOS versions 11.x

*NOTE* with the above it will use the radius server to authenticate
your inbound 'telnet' connections.  You will need to create an entry
in your users file similar to the following to allow access:

   !root   Password == "somepass"
           Service-Type = NAS-Prompt-User

This will let a user in for the first level of access to your Cisco.  You
will still need to 'enable' ( using the locally configured enable secret )
to perform any configuration changes or anything requiring a higher level
of access.  The username '!root' was used as an example here, you can make
this any username you want, of course.

2.  IOS 11.x

For Cisco 11.1, you normally use

    aaa new-model
    aaa authentication ppp radppp if-needed radius
    aaa authorization network radius none
    aaa accounting network wait-start radius

to get the Cisco to talk to a radius server.

With IOS 11.3, you need to add:

    aaa accounting update newinfo

If you want the IP address of the user to show up in the radutmp file
(and thus, the output of "radwho").

This is because with IOS 11.3, the Cisco first sends a "Start" accounting
packet without the IP address included. By setting "update newinfo" it
will send an account "Alive" packet which updates the information. Cistron
Radius understands the "Alive" packet since 1.5.4.3-beta7.


Also you might see a lot of "duplicates" in the logfile. That can be
fixed by

    aaa accounting network wait radius
    radius-server timeout 3


4.  CREDITS

Original  - Alan DeKok <aland@ox.org>
12.x Info - Chris Parker <cparker@starnetusa.net>  2000-10-12

