Installing and Configuring Windows Server 2003 RADIUS Support for VPN Clients – Including Support for EAP/TLS Authentication
Some organizations may prefer to not join the ISA Server firewall/VPN server to their internal network domain. The primary reason for not joining the ISA Server firewall/VPN server to the internal network domain is to prevent potential intruders from using the firewall as a launch point for an attack on the internal network domain. While the probability of the firewall being compromised is very small, it is a fact that the ISA Server firewall is a bastion host and it is exposed to direct attack from the Internet.
The only user accounts available to the machine are those configured in the local user database when the ISA Server firewall/VPN server is not joined to the internal network domain,. In this scenario, all user accounts need to be input into the local user database on the ISA Server firewall/VPN server machine. There is a lot administrative overhead when you mirror your internal network user database, including both user names and passwords, onto the ISA Server firewall/VPN server's local SAM database.
A better solution is to use the Microsoft Windows Server 2003 Internet Authentication Service (IAS). The Microsoft IAS Server is a Remote Authentication Dial In User Service (RADIUS) server. A RADIUS server accepts authentication requests from the ISA Server firewall/VPN server and forwards them to an authentication server. In a Windows Server 2003 domain, the domain controller represents the authentication server. The authentication server confirms or denies the authentication request and forwards the result to the RADIUS server. The RADIUS server forwards it to the ISA Server firewall/VPN server.
The Microsoft IAS Server can also be used to centralize the management of Routing and Remote Access Policy. You may wish to apply the same remote access policies to each server if you have two or more ISA Server firewall/VPN servers. You could manually configure Remote Access Policy on each server using the graphical interface or the netsh command. A better way is to the Microsoft IAS Server. You create Remote Access Policy on the IAS Server and then configure the ISA Server firewall/VPN servers to use the IAS Server of your choice. The policies configured on the IAS Server are applied to incoming VPN connections to the ISA Server firewall/VPN server.
You can also use the IAS Server to support advanced authentication, such as EAP-TLS authentication for PPTP and L2TP/IPSec clients. Advanced authentication methods using EAP enhance the security of your ISA Server firewall/VPN server configuration.
We discuss the following procedures in this ISA Server 2000 VPN Deployment Kit Document:
Installing the Windows Server 2003 IAS Server
Configuring a VPN client Remote Access Policy on the IAS Server
Configuring the ISA Server firewall/VPN server to use the IAS Server for authentication and accounting
Configuring the ISA Server firewall/VPN server to support EAP-TLS authentication for PPTP and L2TP/IPSec clients
Installing and Configuringthe Windows Server 2003 IAS Server
Perform the following steps to install and configure the IAS Server:
1.Click Start, point to Control Panel and click on Add or Remove Programs.
2.Click the Add/Remove Windows Components button in the Add or Remove Programs window.
3.In the Windows Components dialog box (figure 1), select the Networking Services entry and click the Details button.
Figure 1 (1712)
4.In the Networking Services dialog box (figure 2), put a checkmark in the Internet Authentication Service checkbox and then click OK. Click Next in the Windows Components dialog box.
Figure 2 (1713)
5.Click the Finish button on the Completing the Windows Components Wizard page.
Now we'll make some basic configuration changes to the IAS Server.
1.Click Start, point to Administrative Tools and click on Internet Authentication Services.
2.In the Internet Authentication Services console, right click on the Internet Authentication Service (Local) node in the left pane of the console. Click the Register Server in Active Directory command (figure 3).
This setting allows the IAS Server to authenticate users in the Active Directory domain. Click OK in the Register Internet Authentication Server in Active Directory dialog box (figure 4).
Click OK in the Server registered: dialog box (figure 5). This dialog box informs you that the IAS Server was registered in a specific domain and if you want this IAS Server to read users' dial-in properties from other domains, you'll need to enter this server into the RAS/IAS Server Group in that domain.
Figure 3 (1714)
Figure 4 (1715)
Figure 5 (1716)
3.Right click on the RADIUS Clients node in the left pane of the console and click the New RADIUS Client command (figure 6).
Figure 6 (1717)
4.In the New RADIUS Client dialog box, type in a Friendly name for the the ISA Server firewall/VPN server (figure 7). You can use any name you like. In this example we'll use the DNS host name of the ISA Server firewall/VPN server, which is MSFIREWALL1.
Type in either the FQDN or the IP address of the ISA Server firewall/VPN server in the Client address (IP or DNS) dialog box. Do not enter a FQDN if your ISA Server firewall/VPN server has not registered its internal interface IP address with your internal DNS server. You can use the Verify button to test whether the IAS Server can resolve the FQDN (figure 8). Click Next.
Figure 7 (1718)
Figure 8 (1719)
5.On the Addition Information page (figure 9), leave the RADIUS Standard entry in the Client-Vendor drop down list box. Your ISA Server firewall/VPN server will use this setting. Type in a complex shared secret in the Shared secret text both and confirm it in the Confirm shared secret text box.
The shared secret should be a complex string consisting of upper and lower case letters, numbers and symbols. Put a checkmark in the Request must contain the Message Authenticator attribute checkbox. This option enhances the security of the RADIUS messages passed between the ISA Server firewall/VPN and IAS servers. Click Finish.
Figure 9 (1720)
Configuring a VPN Client Remote Access Policy on the IAS Server
You are ready to create a Remote Access Policy on the IAS Server. Remote Access Policies configured on the IAS Server are enforced against VPN clients calling the ISA Server firewall/VPN server. The Windows Server 2003 IAS server has a Remote Access Policy Wizard that makes it easy to create a secure VPN client Remote Access Policy.
Perform the following steps to create a VPN client Remote Access Policy on the IAS Server:
1.In the Internet Authentication Service console, right click on the Remote Access Policies node and click the New Remote Access Policy command (figure 10).
Figure 10 (1721)
2.Click Next on the Welcome to the New Remote Access Policy Wizard page (figure 11).
Figure 11 (1722)
3.On the Policy Configuration Method page (figure 12), select the Use the wizard to set up a typical policy for a common scenario option. In the Policy name text box, type in a name for the policy. In this example, we'll call it VPN Access Policy. Click Next.
Figure 12 (1723)
4.Select the VPN option on the Access Method page (figure 13). This policy is used for all VPN connections. You also have the option to create separate policies for PPTP and L2TP/IPSec VPN links. However, to create separate policies for PPTP and L2TP/IPSec connections, you need to go backwards in the Wizard and create two custom policies. In this example we apply the same policy to all VPN connections. Click Next.
Figure 13 (1724)
5.You can grant access to the VPN server based on user or group (figure 14). The best access control method is on a per-group basis because it confers less administrative overhead. You can create a group such as VPN Users and allow them access, or all your users access. It depends on who you want to give VPN access to the network.
In this example, we will select the Group option and click the Add button. This brings up the Select Groups dialog box. Type in the name of the group in the Enter the object name to select text box and click the Check names button to confirm that you entered the name correctly. Click OK in the Select Groups dialog box and then click Nextin the User or Group Access dialog box.
Figure 14 (1725)
6.You can select the user authentication methods to allow on the Authentication Methods page (figure 15).
You may wish to allow both Microsoft Encrypted Authentication version 2 and Extensible Authentication Protocol (EAP). Both EAP and MS-CHAP version 2 authentication are secure, so we'll select both the Extensible Authentication Protocol (EAP) and Microsoft Encrypted Authentication version 2 (MS-CHAPv2) checkboxes.
Click the down arrow in the Type (based on method of access and network configuration) drop down list box and select the Smart Card or other certificate option then click the Configure button. In the Smart Card or other Certificate Properties dialog box, select the certificate you want the server to use to identify itself to VPN clients. The self-signed certificate appears in the Certificate issued to drop down list box. This certificate is used to identify the server when VPN client are configured to confirm the server's validity. Click OK in the Smart Card or other Certificate Properties dialog box and then click Next.
Note: If you do not see the certificate in the Smart Card or other Certificate Properties dialog box, then restart the RADIUS server and start over. The certificate will then appear in the dialog box after the restart.
Figure 15 (1726)
7.Select the level(s) of encryption you want to enforce on VPN connections (figure 17). All Microsoft clients support the strongest level of encryption. If you have clients that don't support 128 bit encryption, select lower levels, but realize that you lower the level of security provided by the encryption method used by the VPN protocol. In this example we'll select only the Strongest encryption (IPSec Triple DES or MPPE 128-bit) Click Next.
Figure 16 (1727)
8.Review your settings on the Completing the New Remote Access Policy Wizard page and click Finish.
Figure 17 (1728)
Configuring Remote Access Permissions
The new Remote Access Policy requires the connection be a "virtual" or VPN connection. The VPN protocol can be either PPTP or L2TP/IPSec. MS-CHAP v2 or EAP-TLS must be used to authenticate and the client must support the highest level of encryption available for the VPN protocol they use to connect. The user must belong to the Domain Users group in the domain specified in the Remote Access Policy.
The next step is to configure Remote Access Permissions. Remote Access Permissions are different than Remote Access Policies. When a user calls the ISA Server firewall/VPN server, the parameters of the connection are compared against Remote Access Policy or Policies defined on the IAS Server. Remote Access Policies are a hierarchical list The policy on top of the list is evaluated first, then the second listed policy is applied, then the third and so forth.
VPN connection parameters are compared to the conditions of the policy. In the policy we created above, there were two conditions: the connection type is a virtual connection and the user is a member of the Domain Users group. If the connection request matches both of those conditions, then the Remote Access Permission of the account logging in is determined. Remote access permissions are determined differently depending on the type of domain the user account belongs to.
Windows Server 2003 domains do not use the Mixed and Native Mode designations you might be familiar with in Windows 2000 domains. Windows Server 2003 supports domains of varying functional levels. If all the domain controllers in your domain run Windows Server 2003, the default functional level is Windows 2000 mixed. All user accounts are denied VPN (Dial up) access by default in Windows 2000 Mixed Mode functional level. In Windows 2000 Mixed Mode, you must configure each user account to have permission to log on to the VPN server. The reason is that user account permissions override Remote Access Policy permissions in Mixed Mode domains.
If you want to control Remote Access Permissions via Remote Access Policy, you must raise the domain functional level of Windows 2000 Native or Windows Server 2003. The default Remote Access Permission in Windows 2000 and Windows Server 2003 domains is Control access through Remote Access Policy. Once you are able to use Remote Access Policy to assign VPN access permission, you can take advantage of group membership to allow or deny access to the VPN server.
When a connection request matches the conditions in the Remote Access Policy and the user is granted access via either the user account Dial-in settings or Remote Access Policy, the connection parameters are compared a number of settings defined by the Remote Access Profile. If the incoming connection does not comply with the settings in the Remote Access Profile, then the next Remote Access Policy is applied to the connection. If no policy matches the incoming connection's parameters, the connection request to the ISA Server firewall/VPN server is dropped.
The VPN Remote Access Policy you created earlier includes all the parameters required for a secure VPN connection. Your decision now centers on how you want to control Remote Access Permissions:
Allow Remote Access on a per group basis: this requires that you run in Windows 2000 Native or Windows Server 2003 functional level
Allow Remote Access on a per user basis: supported by Windows 2000 Native, Windows 2000 Mixed and Windows Server 2003 functional levels
Allow Remote Access on both a per user and per group basis: this requires Windows 2000 Native or Windows Server 2003 functional level; granular user based access control overriding group based access control is done on a per user basis
Procedures required to allow per user and per group access include:
Change the Dial-in permissions on the user account in the Active Directory to control Remote Access Permission on a per user basis
Change the domain functional level to support Dial-in permissions based on Remote Access Policy
Change the Permissions settings on the Remote Access Policy
Changing the User Account Dial-in Permissions
Perform the following steps if you want to control access on a per user basis:
Click Start, point to Administrative Tools and click on Active Directory Users and Computers.
In the Active Directory Users and Computers console (figure 18), expand your domain name and click on the User node.
Figure 18 (1729)
Double click on a user account in the right pane of the console. In the user account Properties dialog box, click on the Dial-in tab (figure 19). The default setting on the account is Denyaccess. You can allow VPN access for the account by selecting the Allow access option. Per user account setting override permissions set on the Remote Access Policy. Notice the Control access through Remote Access Policy option is disabled. This option is available only when the domain is at the Windows 2000 or Windows Server 2003 functional level.
Figure 19 (1730)
Click Apply and then click OK to commit the Dial-in permission changes you've made to the account.
Changing the Domain Functional Level
If you want to control access on a per group basis, then you will need to change the default domain functional level. Perform the following steps to change the domain functional level:
On a domain controller in your domain, open the Active Directory Domains and Trusts console. Click Start, point to Administrative Tools and click on Active Directory Domains and Trusts (figure 20).
Figure 20 (1731)
In the Active Directory Domains and Trusts console, right click on your domain and click on the Raise Domain Functional Level command (figure 21).
Figure 21 (1732)
In the Raise Domain Functional Level dialog box (figure 22), click the down arrow in the Select an available domain functional level drop down list, select either Windows 2000 native or Windows Server 2003, depending on the type of domain functional level your network can support. Click the Raise button after making your selection.
Figure 22 (1733)
Click OK in the Raise Domain Functional Level dialog box (figure 23). This dialog box explains the change affects the entire domain and after the change is made, it cannot be reversed.
Figure 23 (1734)
Click OK in the Raise Domain Functional Level dialog box (figure 24) informing you that the functional level was raised successfully. Note that you do not need to restart the computer for the changes to take effect. However, the default Remote Access Permission will not change for user accounts until Active Directory replication and completed.
Figure 24 (1735)
Return to the Active Directory Users and Computers console and double click on a user account. Click on the Dial-in tab in the user's Properties dialog box (figure 25). Notice how the Control access through Remote Access Policy option is enabled and selected by default.
Figure 25 (1736)
Controlling Remote Access Permission via Remote Access Policy
Now that you have the option to control access via Remote Access Policy, let's see how VPN access control via Remote Access Policy is performed:
Click Start, point to Administrative Tools and click on Internet Authentication Service.
Click on the Remote Access Policies node in the left pane of the console (figure 26). You will see the VPN Access Policy you created and two other, built-in Remote Access Policies. You can delete these other Remote Access Policies if you require only VPN connections to your ISA Server firewall/VPN server. Right click on the Connections to other access servers Remote Access Policy and click Delete. Repeat with the Connections to Microsoft Routing and Remote Access server Remote Access Policy.
Figure 26 (1737)
Double click on the VPN Access Policy in the right pane of the console. In the VPN Access Policy Properties dialog box (figure 27) there are two options that control access permissions based on Remote Access Policy:
·Deny remote access permission
·Grant remote access permission
Notice that this dialog box does inform you that the user account settings override the Remote Access Permission settings: Unless individual access permissions are specified in the user profile, this policy controls access to the network. Select the Grant remote access permission to allow members of the Domain Users group access to the VPN server.
Figure 27 (1738)
Click Apply and then click OK in the VPN Access Policy Properties dialog box to save the changes.
Configuring the ISA Server firewall/VPN Server to Support RADIUS and EAP-TLS Authentication for PPTP and L2TP/IPSec VPN Clients
The next step is to configure the ISA Server firewall/VPN server to support RADIUS and EAP/TLS authentication. Perform the following steps to configure the ISA Server firewall/VPN server:
Confirm that you have enabled the ISA Server firewall as a VPN Server. Please refer to ISA Server 2000 VPN Deployment Kit document Configuring the Windows Server 2003 ISA Server 2000/VPN Server for details on how to configure the ISA Server firewall as a VPN server.
Click Start, point to Administrative Tools and click on Routing and Remote Access. In the Routing and Remote Access console, right click on your server name and click the Properties command.
Click on the Security tab in the server's Properties dialog box.
Click the Configure button that lies to the right of the Authentication provider drop down list box. In the RADIUS Authentication dialog box (figure 28), click the Add button.
In the Add RADIUS Server dialog box, type in the FQDN or IP address of your IAS Server. Make sure that your ISA Server firewall/VPN server can resolve the FQDN of the IAS Server to the correct IP address. If you are not sure if the ISA Server firewall/VPN server can correctly resolve the FQDN of the IAS Server, use the IP address instead. Click the Change button.
Type in the shared secret you configured on the IAS Server and then confirm the shared secret. Put a checkmark in the Always use message authenticator checkbox.Click OK in the Change Secret dialog box, then click OK in the Add RADIUS Server dialog box, then click OK in the RADIUS Authentication dialog box. Click Apply in the server's Properties dialog box.
Note You do not need to click on the Authentication Methods button that lies just under the Authentication Provider drop down list. This button allows you to configure authentication methods used by the ISA Server firewall/VPN server when using Windows Authentication instead of RADIUS Authentication.
Figure 28 (1739)
Click No in the Routing and Remote Access dialog box that informs you that you selected one or more authentication methods and would you like to view the Help topic.
Click OK in the Routing and Remote Access dialog box (figure 29) informing that you must restart the Routing and Remote Access.
Figure 29 (1740)
Click OK in the Routing and Remote Access Properties dialog box.
Right click on the Routing and Remote Access node in the left pane of the console, point to the All Tasks command and click the Restart command.
Figure 30 (1741)
The ISA Server firewall/VPN server is now ready to support VPN PPTP VPN connections using either MS-CHAP version 2 or certificate based EAP/TLS authentication. Note that while we have configured RADIUS policy to support certificate based EAP/TLS authentication, the certificate used in this policy does not support L2TP/IPSec. You must assign a machine certificate to the ISA Server firewall/VPN server, and the VPN client making the L2TP/IPSec connection request must trust that certificate.
User Service (RADIUS) has been around for what seems like forever, RADIUS has long been the authentication mechanism of choice for Internet Service Providers. Even so, RADIUS is capable of so much more than just being a gatekeeper for ISPs. In this article, I want to discuss some of the lesser known uses for RADIUS. As I do, I also I also want to show you some ways that RADIUS can be integrated into larger networks.
Before I begin
Before I get started, there are a couple of things that I want to get out of the way. First of all, as you probably know, there are a lot of different types of RADIUS servers, as well as a lot of different ways of configuring a RADIUS server to provide authentication to remote users. For the purposes of this article, all of my examples will assume that the RADIUS server is a Windows 2003 Server running Internet Authentication Service (IAS). IAS is Microsoft's version of RADIUS. I am also assuming that the RADIUS servers in my examples later on are using Windows Server 2003domain controllers as their source of user account information.
The other thing that I want to mention is that in some of the examples that I will give later on, I have "dumbed down" some networking concepts in order to be able to focus primarily on RADIUS. For example, later on I will be talking a lot about using wireless networks. In the real world, it is common for wireless networks to be setup similarly to a VPN. However, I am going to simplify my discussions of wireless networks so that I can stay focused on RADIUS rather than getting hung up on the details of wireless security.
Internet service providers
As I mentioned earlier, RADIUS has been around for a long time, but Internet Service Providers were the ones that really made RADIUS famous. That being the case, I want to start out by examining a RADIUS deployment that might be used by an ISP. I know that I said that I wanted to talk about some of the less common types of RADIUS deployments, but looking at an ISP style deployment allows me to start out simple with something that I can build on later on.
If you look at Figure A, you will see a diagram that shows four dial up users connecting to a remote network. As you can see in the figure, each dial up user is dialing into a modem bank that is connected to a Routing and Remote Access (RRAS) server. In this example, the RRAS servers are acting as network access servers for the remote users. However, the RRAS servers are not able to authenticate the user's connections on their own. Instead, the RRAS servers forward the remote access requests to the RADIUS server using the RADIUS protocol.
Figure A
This diagram shows how RADIUS might be used in a typical ISP environment.
The RADIUS server receives the request for authentication and initiates communications with a domain controller. The domain controller contains the user account, just as it would if the user were logging into a workstation that was physically connected to the network.
After the user is authenticated, remote access policies that are defined on the RADIUS server are applied to the user's connection. Assuming that the policies authorize the remote connection, then the RADIUS server tells the RRAS server to allow the connection.
Those of you who are new to RADIUS might be wondering why RADIUS is even necessary in this scenario. After all, the RADIUS server is acting as an intermediary between the RRAS server and the domain controller, so why doesn't the RRAS server just go directly to the domain controller for authentication? There are several reasons why the RRAS server doesn't talk directly to the domain controller, but the most important has to do with security.
It's easy to assume that legitimate users are going to be dialing into the network, but in reality you have absolutely no idea who is dialing into the RRAS server until the user is authenticated. The person who is dialing in might be a legitimate remote user, or it could be someone evil who is out to do your network harm.
If there is a chance that someone with malicious intent could be dialing into the RRAS server, then you have to assume that there is at least some chance (albeit a small one) that the malicious user could compromise the RRAS server. If there is a slim possibility that a hacker could gain control over your RRAS server, do you really want that RRAS server to be able to directly talk to your domain controllers? Of course not. Your domain controllers contain account information for every user on your entire network. You want your domain controllers to be as far from a hacker's reach as possible. This is one of the reasons why the RRAS server does not communicate directly with a domain controller.
Corporate RADIUS deployments
Now that I have shown you how an ISP might use RADIUS, I want to show you how RADIUS might be used in a corporate environment. Larger corporations often have remote users who connect to the network in a variety of ways. If you look at Figure B, you will see that in this diagram, remote users are connecting to a corporate network via dial up, Virtual Private Network (VPN), and wireless network links.
Figure B
In a corporate environment, remote users may connect in a variety of ways.
If you look at the top row in this diagram, you will see that it is exactly the same as the ISP scenario that I discussed earlier. A user dials into a modem bank that is connected to a RRAS server. The RRAS server looks to the RADIUS server for authentication, and the RADIUS server in turn checks the user's credentials against a domain controller. Assuming that the credentials that the user entered were valid, the domain controller validates the credentials, and then the RADIUS server looks at the remote access policy for the user and approves the connection. This approval is passed on to the RRAS server, and the remote user is allowed to access network resources.
If you look at the middle row of computers in Figure B, you can see that the same RADIUS server can also service VPN clients. In a VPN environment, the remote user tunnels through the Internet to the corporate VPN server. Before the VPN server will allow the remote user to access any network resources though, the remote user's identity must be validated.The user enters their credentials, which are then passed to the RADIUS server.The RADIUS server in turn checks the user's credentials against a domain controller. Assuming that the credentials that the user entered were valid, the domain controller validates the credentials, and then the RADIUS server looks at the remote access policy for the user and approves the connection. This approval is passed back to the VPN server, and the remote user is allowed to access network resources.
If this procedure sounds familiar, it's no coincidence. There are lots of VPN solutions on the market, but the Windows Server 2003 based VPN solution is built in to RRAS.In this particular diagram, I am using two different servers to provide access to dial in users and VPN users. I did this for both clarity, and because in larger environments, multiple servers would usually be used. In a small environment though, there is no reason why a single server could not function as both a remote access server and a VPN server.
The bottom row of the diagram shown in Figure B shows a wireless user authenticating through a RADIUS server. In this particular diagram, the wireless access point is acting as a wireless gateway and is connected directly to the RADIUS server. It is not uncommon though for a wireless access point to be connected to a VPN server and for wireless clients to be treated as VPN clients.
Performing double duty
The next thing that I want to show you is that it is possible for a Windows Server 2003 based RADIUS server to be schizophrenic. If you look at Figure C, you will see that the RADIUS server in the diagram is simultaneously functioning as both a RADIUS server and as a RRAS server (in this case an RRAS based VPN server).
Figure C
It is possible for a Windows Server 2003 based RADIUS server to also act as a RRAS server.
Unfortunately, this diagram is probably not as clear as it should be. When I created the diagram, I wanted to show that the RADIUS server contained two different NICs, but I could not find any icons that looked like network cards. Instead, I drew a vertical line down the middle of the server to show that the server is split into two sections.
In this particular deployment, the RADIUS server is multihomed. The RRAS service is bound to one NIC, and RADIUS is bound to another NIC. In this way, the server is acting similarly to a router.
In this particular diagram, the RRAS portion of the server is servicing VPN clients, but it could really be performing any remote access duty. In this case though, the remote users tunnel through the Internet and establish a remote connection to the RRAS / VPN server. As was the case before, the user's identity needs to be authenticated before the VPN server will give the remote user access to any network resources. The VPN server hands the authentication responsibility off to the RADIUS server, which happens to be running on the same box.
You will notice in the diagram that RADIUS is bound to a separate network interface than RRAS. This prevents a domain controller from being directly accessible over the Internet. Instead, the RADIUS server contacts the domain controller over its own interface and validates the user's credentials. After the credentials have been validated and the user's remote access policy is confirmed, the VPN server is informed, and the remote user is given access to network resources.
There is one more thing that I want to show you about this diagram before I move on. Notice that the dial-up and wireless interfaces are both connected to their own RRAS servers. These RRAS servers are multihomed, and one of the interfaces connects to the same network as the RADIUS server. They are not connected to the same interface as the RRAS portion of the RADIUS server.
A RADIUS proxy
In the last three diagrams that I have shown you, the organization has had remote users connecting through dial-up, VPN, and wireless links. In real life, if a company has that many remote users, then there is a good chance that the RADIUS server could become overloaded, and have trouble processing all of the authentication requests in a timely manner.
If you look at Figure D, you will see that the various remote access servers are now connecting to a RADIUS proxy rather than directly to a RADIUS server. The RADIUS proxy's job is to provide RADIUS load balancing services. As authentication requests come in to the RADIUS proxy, the requests are evenly distributed to the back end RADIUS servers for processing. This prevents any one individual RADIUS server from becoming a bottleneck due to an excessive workload.
Figure D
A RADIUS proxy can distribute the authentication workload.
The domain controllers are not shown in this diagram, but most networks include multiple domain controllers. In this type of deployment, the multiple RADIUS servers would be able to check user's credentials against multiple domain controllers. Again, this would prevent a single network component (with the possible exception of the RADIUS proxy itself) from becoming a bottleneck
Today i am dicussing with you guys a trick through which you can share files and folders between Linux and windows. For this purpose you have to enable SAMBA server configuration to allow sharing between windows and Linux. You can share file.folder in a workgroup as RHEL5WORKGROUP or browseable also yes, and now share from folder/ common/ folder. Firstly install the samba server then on the service type chkcongig smb on and then append the following configuration file
root@rhel5 ~]# vim /etc/samba/smb. conf Go to line 74: change workgroup as RHEL5WORKGROUP workgroup = RHEL5WORKGROUP server string = Samba Server Version %v
Edit the last seven lines in /etc/smb.conf Before edit configuration file in last seven lines ; [public] ; comment = Public Stuff ; path = /home/samba ; public = yes ; writable = yes ; printable = no ; write list = +staff Remove the semicolon by through removing these semicolons the disabled lines gets enabled.
After edit [change public as common and path is equal to /common/folder and browseable as yes] [common] path = /common/folder public = no writable = no printable = no browseable = yes
IP address Classes | IP Address Classes With Network Id And Host Id Class A,B,C,D
IP address is 32 bit number. 32 bit number has two portion network portion & host portion. 32 bits number are divided into four octets so each octets has 8bits.Binary digit can converted into decimal and they are represented into dotted decimal format. The value of each octet can vary from 0 to 255. Class A:Class A IP address structure. NNNNNNNN: HHHHHHHH: HHHHHHHH: HHHHHHHH N-network H-Host Ex IP : 10.0.0.1 subnetMask:255. 0.0.0 Value of the first bytes: 1 to 126 No of the network: 126 No of the Host: (256*256*256) -2=16,777, 216-2=16,777,214 Because two hosts we are not using so we reduce 2. X.0.0.0 and x.255.255.255 Purpose: we can use class A with large network with many devices because it contains too many host on the same network 16,777,214-host.
Class B: Class B IP address structure. NNNNNNNN: NNNNNNNN: HHHHHHHH: HHHHHHHH N-network H-Host Ex IP: 130.10.0.1 subnetMask:255. 255.0.0 Value of the first bytes: 128-191 No of the network: (191-127)*256=16,384 No of the Host: (256*256)-2= 65,536-2=65,534 Because two hosts we are not using so we reduce 2. X.X.0.0 and x.x.255.255 Purpose: we can use class B with Medium network with many devices because it contains host on the same network 65,534-host.
Class C: Class C IP address structure. NNNNNNNN: NNNNNNNN: NNNNNNNN: HHHHHHHH N-network H-Host Ex IP: 192.168.5.1 subnetMask:255. 255.255.0 Value of the first bytes: 223-192 No of the network: (223-191)*256* 256=2,097,152 No of the Host: (256)-2=254 Because two hosts we are not using so we reduce 2. X.X.0.0 and x.x.255.255 Purpose: we can use class c with small network because it contains very low no of host on the same network 254-host.
Class D: Range:224-239 Purpose: it is used for multicasting Class E: Range: 240-254 Purpose: now it is not using .Reserved for Future use.
New edition of the world famous Concise Oxford English Dictionary provides an authoritative description of the English language. With instant access to over 240,000 words, phrases, and definitions, this program is ideal for anyone needing an up-to-date dictionary of current English on their PC for study, work, or home.
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