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Ask the Expert- SD-WAN

Cisco - Configuration RADIUS PROXY with Cisco ACS 5.1

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Cisco ACS 5.1 can act as  radius proxy server, it accepts the authentication, accounting, authorization request from the NAS and forwards it to external radius server. It accepts the failure or success results of the requests and sends back to NAS.

 

ACS can simultaneously act as a proxy server to multiple external RADIUS servers.

 

Steps to create proxy server:-

 

Go to Network Resources > External RADIUS Servers> create > click the external radius server name and edit Name----external radius server

Ip address: x.x.x.x

Shared secret key: cisxx123

Advance options:

Authentication port:1812

Acct port:1813

Server timeout: default is 5 sec (can vary from 1 to 120 sec)

Connection attempts: default is 3 (can vary from 1 to 10)

Go to access policy> create a new service  using (User Selected Service Type—RADIUS Proxy) (don't user predefined template) >  Select the external RADIUS servers to be used for proxy and move them to the Selected External RADIUS Servers list.

 

 

Before you do above mentioned steps, please do verify that you can ping tp external radius server through ACS 5.1. Go to launch monitoring and reports > connectivity > type in ip address of radius server and ping.

 

Scenario 2:

Problem:

The basic Summary is that User want to have TACACS+ and local login to the router over the vty lines.  So I made the two groups below.  Goody obviously is what is going to use TACACS and Console uses the local logins.  I split them between 0-4 and 5-15.  It seems that whichever one is higher get the first priority for authentication.  If I move Console to 0-4, then local users work and TACACS do not.   If I have 

Goody at 0 4, then TACACS works, but local does not.  I know I'm probably missing something simple.  Having two TACACS servers, I doubt both will ever be down, but in the event I would like Local 

usernames to work.   If I apply an access list to 0 4 and use SSH,  and a different access list to 5 15 and use telnet it seems to work that way but doesn't help me if the internet goes down and I am onsite trying to 

access the router via SSH. 

aaa authentication login Goody group tacacs+ local
aaa authentication login Console local

line con 0
 login authentication Console
line aux 0
line vty 0 4
 session-timeout 7
 exec-timeout 5 0
 login authentication Goody
 transport input ssh
line vty 5 15
 session-timeout 7
 exec-timeout 5 0
 login authentication Console
 transport input ssh

 

Solution:

Correct me if I not understanding this correctly but you want to use TACACS servers for ssh/console type authentication and if they fail, you want the network device to use its local database. If that is correct then 

you should not need to split the lines and assign them different authentication lists. The first commend that you have: 

aaa authentication login Goody group tacacs+ local

Lists both the tacacs+ and the local database as possible authentication methods. They will be processed in the order they are configured, so the device will:

1. Utilize your TACACS+ servers

2. If the TACACS+ servers become unreachable then the local data base will be used

You can test this by assigning "Goody" to all of your vty lines and then make your TACACS+ servers unavailable. To make that possible you can:

  • Reboot the server
  • Shutdown the server interface
  • Disconnect the network device from its uplink
  • Create an access-list on the uplink interface and block connection to the IP addresses of the TACACS+ servers

 

Comments

I just want to thank you for the doc Venay.

I am glad to be the first one to comment after about 3 years of posting the doc. :)

Beginner

and i want to be the second. your articles helped me with machine+user auth and with remote vpn access with external radius server.

thx mate.