Lesson 3: Configuring IPSec

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After IPSec is configured on a computer, IPSec’s behavior is determined by the policies that you configure. An IPSec policy consists of IP filter lists, filter actions, and authentication requirements. Combined, these components enable an IPSec policy to identify traffic that should be blocked or permitted, or that requires authentication. Figure 8.6 shows how IP filters, IP filter lists, filter actions, and rules define an IP security policy.

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Figure 8.6: IP security policy components

After this lesson, you will be able to

  • Describe the components that make up an IPSec policy: IP filters, filter actions, and IP security rules.

  • Configure IPSec security policies using graphical or command-line tools.

  • Configure CRL checking on Windows 2000–based computers that use IPSec public key certificates authentication.

Estimated lesson time: 60 minutes

IP Filters

IP filters describe network traffic and are used by IPSec policies to determine whether an IP security rule should apply to an individual packet. IP filters can specify traffic to or from a set of IP addresses, WINS servers, DNS servers, DHCP servers, or a default gateway. You can also configure an IP filter to match a packet’s source or destination port number, or even a packet’s IP protocol number. Each of the following examples can be specified by either a single IPSec IP filter or a combination of multiple filters:

  • All traffic to or from IP address 10.4.22.17

  • All Internet Control Message Protocol (ICMP) traffic to or from the default gateway

  • All traffic sent to TCP port 80, except traffic sent from the internal network

  • All outbound connections, except those to specific servers

Multiple IP filters can be combined into an IP filter list. In fact, adding an IP filter to an IP filter list is the only thing you can do with an IP filter, because IPSec policies only allow you to specify IP filter lists. If your needs are simple, you can make an IP filter list that consists of a single IP filter. However, most IP filter lists will consist of multiple IP filters.

To add, remove, or modify an IP filter list, right-click the applicable IP Security Policies node in the Group Policy Object Editor or IP Security Policy Management snap-in, and then click Manage IP Filter Lists And Filter Actions. This opens the Manage IP Filter Lists And Filter Actions dialog box. Click the Manage IP Filter Lists tab. You can then click the Add, Edit, or Remove buttons, as shown in Figure 8.7.

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Figure 8.7: The Manage IP Filter Lists And Filter Actions dialog box

Clicking Add in the Manage IP Filter Lists And Filter Actions dialog box opens the IP Filter List dialog box. Clicking Add in this dialog box, in turn, allows you to create IP filters. You have the option of using a wizard to create the IP filter, but the configuration options are so simple that the wizard is not very useful. Regardless of how you configure the filter, the configuration options are the same: Source Address, Destination Address, Mirrored, and Protocol Type.

The source and destination addresses provide identical options. Selecting My IP Address specifies any of the IP addresses configured on the computer. You should use this option in all filters except those for which traffic is passing through the computer. In other words, you should choose My IP Address instead of Any IP Address unless the computer is acting as a firewall, a router, or an IPSec tunnel endpoint. The A Specific IP Subnet and A Specific IP Address options are self-explanatory. They should be used to create IP filters that specify the intranet, the extranet, or specific computers. For example, if you plan to host a Web server that is accessible from the public Internet but requires encryption for traffic originating on the intranet, you should create an IPSec policy with a filter list specifying the IP subnets on your intranet.

If you select the Mirrored check box, it does not matter which addresses you specify for source or destination, because the IP filter will also match traffic where the packet’s source IP address matches the filter’s destination IP address, and vice versa. You should not select the Mirrored option if creating a filter for an IPSec tunnel, however.

The A Specific DNS Name option is misleading; it does not store the host name in the IP filter. Instead, it looks up the IP address associated with the host name you specify at the time you create the filter and stores the IP address. This is an important distinction because if you create an IP filter that specifies the host name of a computer, and later change that computer’s IP address, the IP filter will no longer match traffic from that computer.

In contrast, the DNS Servers, WINS Servers, DHCP Servers, and Default Gateway address options are all built dynamically. Each time an IPSec policy that uses the filter list is used, IPSec will effectively retrieve the list of DNS, WINS, DHCP, or default gateways from the computer’s network configuration and attempt to match the traffic to those addresses. This allows you to use these dynamic addresses when deploying IPSec policies to an entire enterprise. If various parts of the organization use different servers, or if server addresses change over time, the dynamic IP filters will still function correctly.

Windows Server 2003 provides two built-in filter lists: All ICMP Traffic and All IP Traffic. You can use All ICMP Traffic to match requests from applications such as Ping and Tracert. As the name indicates, you can use All IP Traffic to match any incoming or outgoing IP traffic.

Filter Actions

You use filter actions, also referred to as security methods, to define how an IPSec policy should handle traffic that matches an IP filter. A filter action responds in one of three ways: it drops the traffic, it allows the traffic, or it attempts to negotiate security. If you choose the Permit or Block options for a filter action, there is nothing left to configure. In fact, you never need more than one filter action for each of the Permit and Block options.

There are several additional settings to consider when you configure a filter action to negotiate security. First, you must choose whether the server will allow communications with clients that do not support IPSec by selecting or clearing the Allow Unsecured Communication With Non-IPSec-Aware Computers check box. You can only require IPSec when you have only IPSec-enabled all client computers. Otherwise, clients without IPSec will be denied access to the server. Generally, this setting is enabled only when Active Directory is used to deploy IPSec configuration settings to all networked computers.

You should use the Filter Action Wizard to configure filter actions whenever possible, because configuring integrity and encryption settings can be complicated. The IP Traffic Security page of the wizard enables you to specify the protection suites associated with the filter action. You can choose Integrity And Encryption, Integrity Only, or Custom. If you select Integrity And Encryption, the wizard configures the filter action with ESP-based integrity verification (using Secure Hash Algorithm 1 [SHA1] by default) and encryption (using 3DES by default). If you select Integrity Only, Triple-Data Encryption Standard (3DES) encryption is disabled.

By selecting Custom, you can configure the specific algorithms you want to use for integrity and encryption, including the option to use MD5 for integrity instead of the default SHA1, and standard Data Encryption Standard (DES) for encryption instead of the default 3DES. Selecting Custom also gives you the option to change the default settings for Quick Mode key regeneration by specifying a certain amount of time or a specific amount of data. If you select both of the Generate A New Key Every check boxes, as shown in Figure 8.8, IPSec will use Quick Mode negotiation to generate a new session key after the specified number of bytes have been transferred or after the specified number of seconds has elapsed—whichever comes first. If you do not select either check box, IPSec will automatically initiate Quick Mode negotiation every hour or for every 100 megabytes (MB) of data transferred. The more frequently a session key is regenerated, the harder it is for an attacker to decrypt your traffic. However, regenerating session keys adds performance overhead and decreases network throughput.

Off the Record 

The default settings will not have a significant negative impact on performance, so don’t assume that increasing the session key regeneration interval is going to give you a performance boost. In fact, regenerating session keys will have a noticeable negative impact only if you configure the session keys to be regenerated extremely frequently—say every few seconds.

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Figure 8.8: Specifying custom data integrity, encryption, and session key settings

You can configure multiple protection suites for a single filter action. If you do, view the filter action’s properties, and use the Move Up and Move Down buttons to specify the priority. IPSec will start negotiations with the first security method in the list. If that fails, IPSec will work its way down the list until a connection is successfully negotiated or until the end of the list is reached. You should order the security methods from most secure to least secure. This will ensure that IPSec will negotiate the most secure connection possible with clients and fall back to less secure communications only when negotiations fail.

Note 

As mentioned in Lesson 1, it is the IPSec client, also referred to as the initiator, that determines the order in which the protection suites are evaluated.

Filter actions have one more security option that cannot be configured from the Filter Action Wizard: Use Session Key Perfect Forward Secrecy (PFS). Selecting this check box specifies that you want to renegotiate new master key keying material each time a new session key is required. Basically, this improves the security of the connection by making it more difficult for an attacker to decrypt the communications. However, it requires additional negotiations between the client and server, which reduces performance.

Off the Record 

Using Session Key PFS discourages only those attackers who use brute- force methods to decrypt traffic, which is an extremely impractical task. Therefore, you should enable PFS only for organizations that have the highest possible security requirements.

To add, remove, or modify a filter action, right-click the applicable IP Security Policies node in the Group Policy Object Editor or IP Security Policy Management snap-in, and then click Manage IP Filter Lists And Filter Actions. This opens the Manage IP Filter Lists And Filter Actions dialog box. Click the Manage Filter Actions tab. You can then click the Add, Edit, or Remove buttons.

Windows Server 2003 provides three built-in filter actions: Permit, Request Security, and Require Security. Permit, obviously, allows traffic to be forwarded. Request Security attempts to negotiate with a client that submits an unsecured connection request. If the client and server cannot agree on a set of IPSec settings, an unsecured connection will be established. Require Security also attempts to negotiate an authenticated and encrypted connection with the client, but it will drop the connection if negotiation fails.

IP Security Rules

An IP security rule consists of an IP filter list, a filter action, and, optionally, a connection type and tunnel endpoint. You can specify only one IP filter list and one filter action per rule. If the rule pertains to traffic traveling between networks across an IPSec tunnel, you should provide the IP address of the tunnel endpoint. This does not conflict with your ability to add IP filter lists; you can configure an endpoint and apply the rule only to traffic on a specific subnet within the destination network accessible through the IPSec tunnel.

The default response rule is used to configure the computer to respond to requests for secure communication when no other rules match the traffic. If an active policy does not have a rule defined for a computer that is requesting secure communication, the default response rule is applied and security is negotiated. For example, when Computer A communicates securely with Computer B, and Computer B does not have an inbound filter defined for Computer A, the default response rule is used.

Note 

The default response rule cannot be deleted, but it can be deactivated. It is activated by default for all policies.

To avoid the security risks related to unwanted security negotiations, you can disable the default response rule. Attackers can use the IPSec negotiation process enabled by the default response rule to obtain information about the computer through the security negotiation. A skilled Internet attacker can construct specific security negotiation requests to query and obtain the name of the client, trust relationships, and other settings that are configured in the default response rule. For example, if you use Kerberos as the authentication method for the default response rule, an attacker can query the Kerberos identity of the client. The query results will provide the attacker with the computer name and domain hierarchy, such as username@contoso.com. If you use certificate-based authentication as the authentication method for the default response rule, the attacker might be able to obtain the names of the PKI trusted root CAs that are configured for the default response rule.

You must also configure the authentication method. You can only configure a single authentication method by using the IP Security Policy Wizard, but you can later edit the properties of the policy to add additional authentication methods. You have three authentication methods to choose from: Active Directory, certificates, and preshared key. For more information about which authentication method to use, refer to Lesson 2.

Note 

If you’re creating a rule that simply blocks or permits traffic, you will not be prompted to choose an authentication method because authentication is not used or required.

Configuring IP Security Policies with Graphical Tools

IP filters, filter actions, and IP security rules are only useful when added to an IP security policy. When configuring IP security policies on the local computer, you can use the IP Security Policy Management snap-in. You can also use the Group Policy Object Editor snap-in to edit either local or domain GPOs. In the Group Policy Object Editor, expand Computer Configuration, Windows Settings, Security Settings, and then click either IP Security Policies On Local Computer or IP Security Policies On Active Directory. Because this node might have several different labels, this chapter will refer to it as simply IP Security Policies.

To create a new security policy, right-click the applicable IP Security Policies node in the Group Policy Object Editor or IP Security Policy Management snap-in, and then click Create IP Security Policy. This opens the IP Security Policy Wizard, which guides you through the process of creating a security policy.

During the configuration process, you will be prompted to activate the default response rule. In most cases, you should enable the default response rule. If you do, you will be prompted to select an authentication method. For more information about rules, see the section “IP Security Rules” in this lesson.

After you create a policy with the IP Security Policy Wizard, you can edit the policy’s properties to add rules or change the name, description, policy change interval, and key exchange settings. The Properties dialog box of the Secure Server (Require Security) IP security policy is shown in Figure 8.9. Use the Rules tab to add, modify, and remove IP security rules. Use the General tab to rename a rule, to modify how often IPSec checks for updates to the policy, and to specify key exchange settings.

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Figure 8.9: Editing IP security policy properties

You can click the Settings button on the General tab of the IP security policy properties dialog box to modify the key exchange settings. When you select the Master Key Perfect Forward Secrecy check box, IPSec will negotiate new master key keying material each time a new session key is required. This makes it more difficult for an attacker to decrypt your communications. However, it also adds performance overhead. If you do not select this check box, which is the default setting, new session keys will be derived from the current master key keying material—a quicker process.

The Methods button on the Key Exchange Settings dialog box opens the Key Exchange Security Methods dialog box, which allows you to control which IKE security methods are used to encrypt credentials during the authentication process. You can add or remove IKE security algorithms and arrange them in the order in which they will be used. IPSec will always attempt to use the first security algorithm before continuing to the remaining algorithms. Unless you have identified unusual security requirements that necessitate changing this list, the default settings should meet your needs.

Windows Server 2003 provides three built-in IP security policies: Client (Respond Only), Server (Request Security), and Secure Server (Require Security). The Client security policy consists only of the default response rule with Kerberos authentication. All computers must have the Client security policy, or another policy with the default response rule, assigned to establish an IPSec connection. If you have servers that will be accessed by clients that might or might not be IPSec-enabled, you should assign the Server (Request Security) built-in policy. If you have servers that should only be accessed by computers that you have configured, you can use Secure Server (Require Security). This policy rejects connection requests from computers that are not IPSec enabled.

Tip 

If you’re managing a computer remotely, be careful about assigning the Secure Server (Require Security) policy, or any other policy that does not allow unsecured communications. You could end up blocking requests from your own computer!

Configuring IP Security Policies with Command-Line Tools

Though you should usually use graphical tools to configure IP security policies, Windows Server 2003 also provides the Netsh command-line tool for scripting IPSec configuration. Netsh is a native Windows Server 2003 command-line scripting tool that you can use to display or modify the local or remote network configuration. The Netsh IPSec commands cannot be used on any other version of Windows.

To use the command line to configure IPSec policies on computers running Windows XP, use Ipseccmd.exe, which is provided on the Windows XP CD, in the \Support\Tools folder. To use the command line to configure IPSec policies on computers running Windows 2000, use Ipsecpol.exe, which is provided with the Windows 2000 Server Resource Kit.

To use Netsh interactively to view or modify IPSec settings, open a command prompt and run the command Netsh with no parameters. This starts the Netsh interactive command prompt. Then type Ipsec static or Ipsec dynamic to set the context for Netsh. For example, the following commands launch Netsh and set the context to Ipsec dynamic:

C:\>netsh netsh>ipsec netsh ipsec>static netsh ipsec static>

Static mode allows you to create, modify, and assign policies without affecting the active IPSec policy. Dynamic mode allows you to display the active state and immediately implement changes to the active IPSec policy. Dynamic Netsh commands affect the service only when it is running. If it is stopped, dynamic policy settings are discarded.

Dynamic mode can be quite useful, for example, if you need to immediately initiate a change to IPSec processing. Although some IPSec commands require you to stop and start the IPSec service, others do not. However, Dynamic mode can also be a mixed blessing. Should you make a mistake in Dynamic mode, you will have no opportunity to discover it before implementing the change. You could end up creating an incorrect configuration without receiving a warning.

Exam Tip 

This chapter will not provide detailed documentation for the dozens of Netsh commands relating to configuring and monitoring IPSec policies. For the exam, you should be familiar with the types of things you can use Netsh for. Explore the commands by reviewing the Netsh documentation in Windows Help And Support Center. However, do not feel like you need to memorize the syntax of all the Netsh commands. Even if you use Netsh to create scripts in the real world, you shouldn’t waste brain cells memorizing the parameters—just refer to them as needed.

Certificate Revocation List Checking

As you learned in Chapter 7, certificate servers issue Certificate Revocation Lists (CRLs) to update clients when certificates are revoked. For a client computer to validate a certificate completely, it must check the CRL to verify that the certificate has not been revoked by the issuer. Because the standards for checking CRLs were still evolving when Windows 2000 was released, computers running Windows 2000 do not automatically check CRLs for certificates used in IPSec authentication. If you plan to use certificates for IPSec authentication and have computers running Windows 2000 on your network, you should enable CRL checking.

To enable CRL checking on computers running Windows 2000:

  1. Under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\PolicyAgent\, add a key named Oakley.

  2. Inside the new Oakley key, add a DWORD entry named StrongCrlCheck.

  3. Assign the StrongCrlCheck entry any value from 0 through 2, where:

    • A value of 0 disables CRL checking (default for Windows 2000).

    • A value of 1 causes CRL checking to be attempted and certificate validation to fail only if the certificate is revoked (default for Windows XP Professional and Windows Server 2003). Other failures that are encountered during CRL checking (such as the revocation URL being unreachable) do not cause certificate validation to fail.

    • A value of 2 enables strong CRL checking, which means that CRL checking is required and that certificate validation fails if any error is encountered during CRL processing. Set this registry value for enhanced security.

  4. Open a command prompt, run the command net stop policyagent, and then type net start policyagent to restart the IPSec-related services.

Windows XP Professional and Windows Server 2003 do automatically check CRLs when authenticating IPSec connections. However, you might want to disable this behavior if you identify CRL checking as the cause of a problem. To disable CRL checking, open a command prompt and run the following command:

netsh ipsec dynamic set config strongcrlcheck 0

Security Alert 

IPSec CRL checking does not guarantee that certificate validation fails immediately when a certificate is revoked. There is a delay between the time when the revoked certificate is placed on an updated and published CRL and the time when the computer that performs the IPSec CRL checking retrieves this CRL. The computer does not retrieve a new CRL until the current CRL has expired or until the next time the CRL is published. For more information about CRLs, refer to Chapter 7.

Practice: Configuring IP Security Policies

In this practice, you will configure two types of IP security policies: one for packet filtering and one for authentication and data integrity.

Exercise 1: Configure Packet Filtering

In this exercise, you will configure packet filtering on Computer1 to allow all traffic from the 192.168.1.0 network, but to allow only Web requests from other networks. First, you will create two IP filter lists to identify internal traffic and Web traffic from any network.

  1. Log on to the cohowinery.com domain on Computer1 using the Administrator account.

  2. Open a blank Microsoft Management Console (MMC) console, and then add the IP Security Policy Management snap-in. When prompted to select the computer or domain, select Local Computer.

  3. Right-click IP Security Policies On Local Computer, and then click Manage IP Filter Lists And Filter Actions.

  4. Click the Manage IP Filter Lists tab, and then click Add.

  5. In the Name field, type External Web Traffic.

  6. Click Add.

    The IP Filter Wizard appears.

  7. Click Next, and then click Next again.

  8. On the IP Traffic Source page, click the Source Address list, and then click Any IP Address. Click Next.

  9. On the IP Traffic Destination page, select My IP Address, and then click Next.

  10. On the IP Protocol Type page, click the Select A Protocol Type list, and then click TCP. Click Next.

  11. On the IP Protocol Port page, click To This Port, and then type 80, as shown in Figure 8.10. Click Next.

    click to expand
    Figure 8.10: Configuring an IP filter list for Web traffic

  12. Click Finish, and then click OK.

  13. In the Manage IP Filter Lists And Filter Actions dialog box, click Add.

  14. In the Name field, type Internal Traffic. Click Add.

    The IP Filter Wizard appears.

  15. Click Next, and then click Next again.

  16. On the IP Traffic Source page, click the Source Address list, and then click A Specific IP Subnet. Type the IP address and subnet mask in the provided fields. For example, if you are using the class C 192.168.1.0 private network, type 192.168.1.0 in the IP Address field, and then type 255.255.255.0 in the Subnet Mask field. Click Next.

  17. On the IP Traffic Destination page, select My IP Address, and then click Next.

  18. On the IP Protocol Type page, click the Select A Protocol Type list, and then click Any. Click Next.

  19. Click Finish, and then click OK.

Next, you will create a filter action to drop traffic:

  1. In the Manage IP Filter Lists And Filter Actions dialog box, click the Manage Filter Actions tab. Click Add.

    The IP Security Filter Action Wizard appears.

  2. Click Next.

  3. On the Filter Action Name page, type Deny in the Name field. Click Next.

  4. On the Filter Action General Options page, click Block. Click Next.

  5. Click Finish, and then click Close.

At this point, you have added an IP filter list and a filter action. However, this does not change the behavior of Computer1. To change the behavior, you must configure an IP security policy. In the IP security policy, you will add three rules to permit internal traffic, to permit external Web traffic, and to block all other traffic.

First, create the security policy:

  1. Right-click IP Security Policies On Local Computer, and then click Create IP Security Policy.

    The IP Security Policy Wizard appears.

  2. Click Next.

  3. On the IP Security Policy Name page, type Packet Filtering in the Name field. Click Next.

  4. On the Requests For Secure Communication page, clear the Activate The Default Response Rule check box, and then click Next.

  5. Leave the Edit Properties check box selected, and then click Finish.

Next, create the first rule to permit all internal traffic:

  1. In the Packet Filtering Properties dialog box, click Add.

  2. The Create IP Security Rule Wizard appears.

  3. Click Next three times.

  4. On the IP Filter List page, click Internal Traffic, and then click Next.

  5. On the Filter Action page, click Permit. Click Next.

  6. Clear the Edit Properties check box, and then click Finish.

Next, create the second rule to permit external Web traffic:

  1. In the Packet Filtering Properties dialog box, click Add.

    The Create IP Security Rule Wizard appears.

  2. Click Next three times.

  3. On the IP Filter List page, click External Web Traffic. Click Next.

  4. On the Filter Action page, click Permit. Click Next.

  5. Clear the Edit Properties check box, and then click Finish.

Next, add the last rule to block all other traffic. Unlike most firewalls, IPSec doesn’t drop traffic by default. Therefore, you needed to explicitly create a rule to drop traffic that was not explicitly permitted.

  1. In the Packet Filtering Properties page, click Add.

    The Create IP Security wizard appears.

  2. Click Next three times.

  3. On the IP Filter List page, click All IP Traffic, and then click Next.

  4. On the Filter Action page, click Deny. Click Next.

  5. Clear the Edit Properties check box, and then click Finish.

  6. Click OK.

There’s one last step: assigning the policy. Right-click Packet Filtering in the right pane of the IP Security Policies snap-in, and then click Assign. The policy will immediately take effect, and traffic from external networks not destined for port 80 will be dropped.

Exercise 2: Enable Encryption and Integrity Verification

In this exercise, you will configure Computer1 and Computer2 to use IPSec for encryption and integrity verification, without interfering with communications from other computers.

  1. If necessary, log on to the cohowinery.com domain on Computer1 using the Administrator account and open a blank MMC console, and then add the IP Security Policy Management snap-in. When prompted to select the computer or domain, select Local Computer.

  2. In the right pane, right-click Server (Request Security), and then click Assign.

  3. Log on to the cohowinery.com domain on Computer2 using the Administrator account.

  4. Open a blank MMC console, and then add the IP Security Policy Management snap-in. When prompted to select the computer or domain, select Local Computer.

  5. Right-click Client (Respond Only), and then click Assign.

    Now all communications between Computer1 and Computer2 will be encrypted and authenticated. Because they are members of the same domain, the default Kerberos authentication protocol configured on the client (Respond Only) and server (Request Security) will successfully authenticate.

Lesson Review

The following questions are intended to reinforce key information presented in this lesson. If you are unable to answer a question, review the lesson materials and try the question again. You can find answers to the questions in the “Questions and Answers” section at the end of this chapter.

  1. Which of the following check boxes, when selected, will result in a performance degradation? (Choose all that apply.)

    1. Master Key Perfect Forward Secrecy (PFS)

    2. Use Session Key Perfect Forward Secrecy (PFS)

    3. Accept Unsecured Communication, But Always Respond Using IPSec

    4. Allow Unsecured Communication With Non-IPSec-Aware Computers

  2. Which of the following command-line tools can be used to configure IPSec? (Choose all that apply.)

    1. Netstat

    2. Net

    3. Netsh

    4. Ipseccmd

    5. Ipconfig

    6. Ipsecpol

Lesson Summary

  • IP filters, IP filter lists, filter actions, and rules define an IP security policy.

  • Windows Server 2003 IP filters can be dynamic, being defined by IPSec based on the host’s network configuration information. Dynamic IP filter lists can be created by using the IP addresses of DNS servers, DHCP servers, WINS servers, and the default gateway.

  • IP security policies can be defined on the local computer by using the IP Security Policy Management snap-in. To configure policy for an entire domain, use Group Policy Object Editor.

  • IP security policies can also be configured from the command line by using Netsh.

  • If you use public key certificates to authenticate IPSec sessions, you should configure Windows 2000 to check CRLs. Windows XP and Windows Server 2003 automatically check CRLs.



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MCSA(s)MCSE Self-Paced Training Kit Exam 70-299 (c) Implementing and Administering Security in a M[.  .. ]twork
MCSA/MCSE Self-Paced Training Kit (Exam 70-299): Implementing and Administering Security in a MicrosoftВ® Windows Server(TM) 2003 Network (Pro-Certification)
ISBN: 073562061X
EAN: 2147483647
Year: 2004
Pages: 217

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