Active Directory Authentication for Cisco Devices – Routers and Switches

Cisco, AAA, Radius, Active Directory, Windows Server 2012 R2, NAP role, NPS its all going on!

Active Directory Authentication for Cisco DevicesJust a quick note to reference the following video on YouTube. This video demonstrates setting up Active Directory Authentication for Cisco Devices, such as Routers and Switches etc. This is using AAA on the router and RADIUS through the Network Access Policy (NAP) role in Windows Server 2012 R2, this in turn enables a Network Policy Server (NPS). The Windows server (the Radius Server) is registered in Active Directory which allows it to query the domain it is connected too for authenticating users in Active Directory to the Cisco IOS devices. You can control who has access to various network devices through rules created on the NPS. This can in turn be achieved in Active Directory via groups, binding those groups to privilege levels to pass through to deifferent devices.

For example you could have a group in AD called Network Admins which is tied to a prilivelge level 15 group rule in the NPS configuration. This rule would pass through the privilege level 15  setting through to the IOS configuration. Members of this AD group upon succesful authentication would then be granted privilege level 15 access on the router or switch.

 

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Cisco Access Control List Guidelines to follow when creating rules.

Cisco Access Control List Guidelines

Just a quick post to remind myself and others ofCisco Access Control List Guidelines. the following Cisco Access Control List Guidelines that we should be aware of. I thought this would be good to post as a quick reference/lookup. This just gives a basic run down of how ACL’s should be implemented as per Cisco CCNA Security.

  • Ensure the last ACE that is processed has a ‘deny any’ or ‘deny any any’
  • ACLs are processed top down, as soon as as an ACE is matched the processing is stopped.
  • Make sure the most specific ACEs are at the top of the list.
  • One ACL per interface, per protocol, per direction.
  • Any new ACE’s that are added to an ACL are added to the bottom by default, unless specified.
  • Router generated traffic is not filtered by outbound ACLs
  • Standard ACLs should be placed as close to the destination as possible.
  • Extended ACLs should be placed as close to the source as possible.
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Cisco Router Password Recovery

Cisco Router Password Recovery Steps.

Cisco Router Password Recovery

As a mental note to myself more than anything however some one may also find this useful. These are the steps you need to take in order to recover or reset a Cisco Router Password. This was performed on 2800 series router. This may be different for other router models and the break key sequence may also be different for your favorite terminal software, however these are the outline steps required in order to re-gain access to you Cisco Router.

  1. Connect via the console port.
  2. Power cycle the router.
  3. Issue the break sequence command on startup within 60 seconds of power up to put into ROMmon – ‘Ctrl-Break’ or ‘Break’
  4. Change the config register with ‘confreg 0x2142’ command.
  5. Power cycle the router.
  6. skip the initial startup/setup procedure
  7. move into privilege EXEC mode.
  8. Copy the startup configuration to the running configuration.
  9. Check the config with a show run – and change the password.
  10. Change the config register back to the original setting (usually 0x2102) in Global Configuration mode with ‘config-register 0x2102’.
  11. Save your changes and reboot to set the new config register.

Issue a ‘Show version’ to verify you have the correct config register:

Router Configuration register 0x2102

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Mitigating VLAN Hopping Attacks

Ways to mitigate VLAN Hopping Attacks on a Cisco Switch.

Cisco Switch mitigating VLAN Hopping Attacks

The ways in which we can prevent basic vlan hopping attacks on a Cisco Switch are more best practice security configurations. Vlan hopping attacks can occur in one of two ways. The first by an attacker spoofing DTP messages directly to a switch, if the switchport has Dynamic Trunking Protocol (DTP) enabled it can then negotiate a vlan and receive tagged packets for that vlan. The second is by introducing a rogue switch and again taking advantage of DTP and negotiating a trunk with the switch and then allowing it to receive all vlans. Not good!

We can do the following to prevent this:

  • Disable Dynamic Trunking Protocol (DTP) for non-trunked ports with switchport mode access – this should always be done for all ports straight out of the box!
  • Disable Dynamic Trunking Protocol (DTP) for all trunked ports with switchport non-negotiate.
  • Manually enable trunk ports with switchport mode trunk.
  • Set the native vlan to an unused vlan rather than just leaving it on vlan1 with switchport trunk native vlan (your vlan number)
  • Put all unused ports into an unused vlan and then disable all unused ports – again disabling all unused ports should be done straight out the box.
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Cisco AAA Authentication with RADIUS against Active Directory 2012 NPS

AAA and RADIUS through the Network Policy Server (NPS) role in Windows Server 2012 R2

I thought I would cover a quick post to demonstrate setting up Active Directory authentication for a Cisco router or switch IOS login. This will be using AAA and RADIUS through the Network Policy Server (NPS) role in Windows Server 2012 R2 to authenticate users in Active Directory on Cisco IOS devices.

As with all my labs a picture paints a thousand words so here is the GNS3 Network topology we will be using, this is also being used for 802.1x which will be covered in later post:

Cisco AAA Authentication with RADIUS against Active Directory GNS3 Topology

So here is quick run down on the gear we will be using just for this lab:

R1: Cisco IOS (C7200-ADVENTERPRISEk9-M), Version 15.2(4)S4

Server 2012 DC: Windows Server 2012 R2 ( Active Directory Domain Services and Network Policy Server role.

Just to demonstrate a lab as simple as the below could also be used to test this:

radius lab

Active Directory Configuration:

I will be assuming that AD and the NPS role have already been installed. Prior to jumping into the NPS configuration you will need to create an AD group for the users that will be logging into the Cisco equipment, add a couple of test users to this group. In my case I have simply created a group called ‘Radius’ and have added the user ‘Adam’.

Open the NPS console.

Right click on the NPS(Local) tree node and select ‘Register server in Active Directory’:

Now create the Radius clients, in our this case this is R1:

Radius Clients, New

New Radius Client Settings

New Radius Client Advanced Screen

 

Now we need to configure the Network policy:

New Network Policy

New Network Policy name

Add our ‘Radius’ AD group. You can tighten the control here by specifying further conditions such as the ‘friendly name’ (R1)  or the local IPV4 address of the radius client, in a production environment you would want to lock this down further for now we are just going to add the the user group to authenticate:

New Network Policy - Add

Grant Access for this group:

New Network Policy Access Granted

Configure the appropriate authentication methods:

New Network Policy - Configure Authentication Methods

Change the Standard Radius Attributes by removing ‘Framed-Protocol – PPP’. Edit the ‘Service-Type’ value to ‘Login’:

New Network Policy - Standard Radius Attributes

Add a Vendor specific attribute, this allows the radius server to pass the privilege level though the cisco router which we shall see later in the debugging. The value needs to read ‘shell:priv-lvl=15′.

You can create several policies for the different privilege levels. For example you could create a group in AD called ‘Cisco Users Priv 1’, associate this group to a policy and in the below option use the value ‘shell:priv-lvl=1′. When that user logs in the policy will match that user and the NPS use the matched policy passing privilege level 1 through to the router or switch.

New Network Policy - Vendor Specific Radius Attributes

Then Finish:

New Network Policy - Finish

Cisco IOS configuration

Create a a user with privilege level 15, we wil use this as our fall back should the router not be able to contact the radius server it will use the local AAA database.

Enable AAA:

Now we will setup the main parts to the radius configuration, tell the switch we would like to use radius and the group RAD_SERVERS:

Specify the radius server that we would like to use in our case 10.0.0.2 is our NPS, the auth and acc ports and also the secure key we used:

Specify that for  the default login  for authentication an authorization that we want to use the group called RAD_SERVERS that we have just created and if that fails we use the local database. This is particularly important so we do not lock ourselves out on the router:

All together this looks like the below:

We can test simply by logging out and back in.

Troubleshooting

It obviously goes without saying you need to test the authentication to the Radius server, exit right out of the console and log back in using your AD credentials.

If all has been configured correctly you should be able to login. its also worth testing the fall back option configured for local AAA authentication. We can do this just simply stopping the NPS service then try the local credentials, again all being configured correctly you should be able to login.

There are a few useful debugging commands we can use  to monitor and troubleshoot the authentication these being:

This time when we login we can see the debug information for an attempted login, it should look similar to this, note the highlighted area’s:

radterm

I hope this has been informative.

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IPV6 and RIP GNS3 Lab

I decided to to look into configuring a quick simple IPV6 lab in GNS3 using RIP. I put together the following lab using the RIP routing protocol for ease of use. The lab consists of  3 routers multiple interfaces, 3 subnets, 3 PC’s and switches for endpoint connectivity, I find its easier to use the virtual switches if I want to expand the lab later. The routers are the using the c7200-adventerprisek9-mz.152-4.S4 image and the PC’s are simply the virtual PCs (VPCS) from GNS3 again for ease of use. I do normally prefer to connect an actual operating system as PC’s as I find it more realistic however as we are just testing connectivity and routing the VPCS option is a good fit here and light on system resources.

Below is the simple topology:

RIP and IPV6 lab
RIP and IPV6 lab

Some of the basic configuration for RIP and IPV6 is show below for R1. This can then be replicated across the other routers and interfaces changing the IPV6 subnet ID and Interface ID as you go along. Using Global IPV6 addresses with a made up subnet ID.

Straight in the configuration starting in global configuration mode on R1:

R1(config)#ipv6 unicast-routing
R1(config)#int fa0/0
R1(config-if)#ipv6 address 2001:db8:6783:120::1/64
R1(config-if)#no shutdown

Verify the interface:

verify the ipv6 interface configuration.
verify the ipv6 interface configuration.

Note the new IPV6 Link Local address that has been automatically assigned to the interface when it was brought up, the closest thing to explaining for now is the 169.254.x.x/16 address asinged by APIPA. The Link Local address is made of the first 10 bits (identifiable as the Link Local FE80) the other 54 bits being Zeros (::) and the remaining 64 bits being made up of the MAC address and FFFE slotted in the middle. 🙂

Onto the routing:

R1(config)#ipv6 router rip RIP1
R1(config)#int fa0/0
R1(config-if)#ipv6 rip RIP1 enable

The router will then advertise its routes through the enabled interface for RIP1 using rip and likewise for R2 and  R3. Once R3 has been configured 30 seconds later a quick check of the routing table from R1 should display:

IPV6 rip routing table
IPV6 rip routing table

We can see the advertised routes for rip, also notice that the advertised route is via its IPV6 Link Local address starting with FE80.

A quick check from PC3 to R1 and PC4 further verifies  connectivity through IPV6 and rip configuration:

Checking IPv6 endpoint connectivity from PC3 to PC1.
Checking endpoint connectivity from PC3 to PC1.

Interesting, more to come from IPV6 in the future for sure.

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CCNA Security – Implementing Cisco Network Security Lab

I thought I would share with you the Lab I have been mostly working with for CCNA  Security (CCNAS) – Implementing Cisco Network Security (210-260) exam that I have recently took and passed. I have also used several smaller lab setups for specific testing however this is the main lab to piece everything together.

CCNAS - Implementing Cisco Network Security Lab
CCNAS – Implementing Cisco Network Security Lab

The lab has been built to accommodate the many elements on the exam and covers off most of the practical procedures that you need to be comfortable with. Using GNS3 and VirtualBox we are able to lab most of the practical exercises bar the L2 switching portions which I achieved through physical equipment (Catalyst 3750, 3550 x2 and 2950 switches). The exam does cover many topics in theory that you must know, these aren’t covered here, however can be found on the Cisco website.

The lab contains several client machines for managing the routers and ASA firewalls from putty, cisco configuration professional and ASDM as well as testing PAT through the ASA with a breakout to the internet. There is an Active Directory Domain Controller with the Network Access Protection role installed for use with AAA/radius and NTP. A separate syslog server. A DMZ with web server for testing NAT and outside firewall rules. There is also an ASA 5520 at each of the three sites for testing VPN site-to-site Ipsec connections, clients at all sites for testing end to end connectivity. There is also an outside remote client for testing the Anyconnect and client-less vpn options which takes advantage of the AAA radius service.

Using this lab we are able to address the following practical elements for the CCNAS exam:

2.0 Secure Access

2.1   Secure management

  • 2.1.b Configure secure network management
  • 2.1.c Configure and verify secure access through SNMP v3 using an ACL
  • 2.1.d Configure and verify security for NTP
  • 2.1.e Use SCP for file transfer

2.2 AAA concepts

  • 2.2.b Configure administrative access on a Cisco router and ASA using RADIUS
  • 2.2.c Verify connectivity on a Cisco router and ASA to a RADIUS server
3.0 VPN

3.2 Remote access VPN

  • 3.2.a Implement basic clientless SSL VPN using ASDM
  • 3.2.b Verify clientless connection
  • 3.2.c Implement basic AnyConnect SSL VPN using ASDM
  • 3.2.d Verify AnyConnect connection
  • 3.2.e Identify endpoint posture assessment

3.3 Site-to-site VPN

  • 3.3.a Implement an IPsec site-to-site VPN with pre-shared key authentication on Cisco routers and ASA firewalls
  • 3.3.b Verify an IPsec site-to-site VPN
4.0 Secure Routing and Switching

4.1 Security on Cisco routers

  • 4.1.a Configure multiple privilege levels
  • 4.1.b Configure Cisco IOS role-based CLI access
  • 4.1.c Implement Cisco IOS resilient configuration

4.2 Securing routing protocols

  • 4.2.a Implement routing update authentication on OSPF
5.0 Cisco Firewall Technologies

5.3 Implement NAT on Cisco ASA 9.x

  • 5.3.a Static
  • 5.3.b Dynamic
  • 5.3.c PAT
  • 5.3.d Policy NAT
  • 5.3 e Verify NAT operations

5.4 Implement zone-based firewall

  • 5.4.a Zone to zone
  • 5.4.b Self zone

5.5 Firewall features on the Cisco Adaptive Security Appliance (ASA) 9.x

  • 5.5.a Configure ASA access management
  • 5.5.b Configure security access policies
  • 5.5.c Configure Cisco ASA interface security levels
  • 5.5.d Configure default Cisco Modular Policy Framework (MPF)

Well what next, CCNP Security of course.

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