Cisco + RADIUS + Windows Server 2008 NPS

One of my latest projects has been to change all the login / enable passwords for our various Cisco routers and switches. We've had some turnover, and frankly, they haven't been changed in many many years.

So, I had one of three options:

• simply change the login passwords and enable passwords. easy.
• move to local database user(s) instead. easy too.
• move to AAA / RADIUS authentication based on Windows 2008 NPS. a little tricky.

I chose the third option.

Why? I like a challenge. No, not really. I chose that because it will make it easier to adjust/change access to the devices whenever we have staffing changes, or whatever. Using Windows 2008 NPS will utilize an Active Directory group - just like all of the other RADIUS stuff we do. It's something we're familiar with.

Let's get going...

First of all - giant shout to @hezetation for this. Hez & I are friends and we worked together at a previous employer AND he's a very sharp Cisco / Apple guy (what? you can like both Cisco & Apple at the same time?). As I got going, and then eventually stuck (more on that later) - Hez was a great resource. Two thumbs up. Thanks dude!

Cisco Config
So - let's get going on the config changes needed for the Cisco gear. The below is the example from my home router - a Cisco 871W that gives me internet access and also VPN acces back to the "home office" in Oklahoma.

First of all, we need a local username - so we can still get to the devices incase RADIUS goes down

#username privilege 15 password 7 013B072C5A26070B2475411C350A18192218313A6A671F1A1B

Next we need to add the actual AAA (Radius) stuff.

aaa new-model
aaa authentication login group radius local
aaa authorization exec group radius local

Next we'll adjust the radius access itself

ip radius source-interface bvi1
radius-server host key 7 013B072C5A26070B2475411C350A18192218313A6A671F1A1B

Finally we'll change the config for the con / vty ports

line con 0
authorization exec
login authentication
line vty 0 4
authorization exec
login authentication

That's it. Seriously. You're done on the Cisco side.

Windows Server 2008 NPS Config
This was the trickier part. In our environment, we're already using Windows Server 2008 NPS for our Cisco VPN & Ruckus Wireless setup. All I'm doing here is adding additional functionality. No problem. Let's get going.

Let's start by creating some clients - these will be our various Cisco Devices - routers & switches and such. Head over to NPS - Network Policy Server applet, expand on RADIUS Clients and Servers, Right-click on RADIUS Clients and choose New.

Yup, just like that. Now, let's enter useful information.

Notice that I'm starting my "Friendly name" with "Cisco-" (more on that later). The shared secret is the same shared secret that I entered above in the Cisco config section under radius-server key. They need to match. Click on the Advanced tab.

Let's choose the Vendor Name of Cisco. This DOES work with "RADIUS Standard" - but - for fun - let's choose Cisco. We're done. Click OK.

Now, head back to the NPS. Right-click on Network Policies, and choose New.

Alrighty, here some screen shot galore. Follow along.

Give your new policy a name - something useful to you so you know which one it is - especially if you have several different policies. Unspecified is fine for the type of NAS. Click Next.

Okay, let's add some conditions. Click Add.

We'll restrict login to people based on AD membership - so - choose Windows Groups, and click Add.

Click Add Groups

We want RADIUS Admins - Click OK. Click OK again.

Good. Now, we also want to apply this to the various RADIUS Clients that are important to us - you know, the ones that start with "Cisco-" - click Add.

What we want is "Client Friendly Name" - Click Add.

And we want any RADIUS client that starts with "Cisco-" - so - enter "Cisco-?" and click OK.

Looks good so far. Click Next.

Access Granted. Yes please. Click Next.

Make sure PAP is checked. Click Next. No need to read the "help" if you don't want.

No constraints to deal with. Click Next.

Here comes the fun. Remove both the PPP & Framed attributes. Then click Add.

Choose Service-Type. Click Add.

Choose "Others" and "Login" - Click OK & Close.

That's all for Standard. Now, click on Vendor Specific.

Great. Click Add.

Choose Vendor-Specific and click Add.

Choose "Cisco" as your vendor. Yes, this conforms to RADIUS RFC. Click Configure Attribute.

This string is what gives successful authentication "enable" or "privilege 15" access on the Cisco gear. Make the appropriate changes. Click OK. Click OK again.

Looks good. Click OK again. Click Close.

I used the defaults for all the rest of the NAP / RRA stuff above. Click Next.

All that looks good. Notice my name here is "CiscoDevicesAdmins2" - this is the 2nd time I did this and I cannot find my first screen shot. Pay no attention to that. Oopsie! :) Click Finish

Let's Test
Great! Now, let's test this sucker. We're going to telnet to my 871W router - 10.3.20.1 is the IP address. Let's go do it! Drop to terminal...

What? "This line may not run PPP." What does that mean? Let's go check out the logs on NPS first.

Here's the log entry. As I look at it more closely, I'm granted full access. NPS did it's job. What in the world? Why can I not get access to my router? Time for some Google-fu...

So, as you google for the phrase "This line may not run PPP." as it relates to Cisco / RADIUS, you'll find a ton of people with the same problem. And, all of them have this issue on Server 2008 NPS. Why is that?

Well, this is where @hezetation becomes a hero! He lets me screen share his setup and poke through each and every window and session and attribute. Our Network Policies are identical (minus the name). So, we then talk about "global" policies and Hez has an "ah ha!" moment...

The Fix
So, I have a single Connection Request "global" policy - let's go to NPS and look at that.

The "WindowsAuthentication" policy overrides the others with certain settings... so... go to properties, Settings...

Check that out. PPP. Right there under RADIUS Attributes -> Standard. I don't need that. I have specific Network Policies to handle VPN/RADIUS and such. Let's remove both of those - the PPP / Framed settings and click OK to apply the changes.

Test Again
Right - now - let's test again... drop to terminal...

SUCCESS! YAY!

Okay - so - that's that. I had the policy and Cisco configs right. What I missed was the fact that under Server 2008 NPS, the Connection Request Policy settings could override (globally) individual Network Policies. Good info to know.

Next step - figuring this out for our various Dell PowerConnect switches (random 3000 and 5000 and 6000 series) that we have in production... won't THAT be fun...

//Update 9-15-2010 - I have added our various Cisco 1100 series APs into our AAA / RADIUS (admin) setup and these instructions worked the same way as they did for routers / switches / etc. This works just fine.

Hope this helps someone.

Refer to http://www.darylhunter.me/blog/2010/06/cisco-ios-fu-7-cisco-radius-windows-server-2008-nps.html