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Goals. Design the DHCP infrastructure Design the remote access infrastructure Design remote access policies. (Skill 1). Designing the DHCP Infrastructure. Dynamic Host Configuration Protocol (DHCP) A simple, but critical, service Functionality
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Goals • Design the DHCP infrastructure • Design the remote access infrastructure • Design remote access policies
(Skill 1) Designing the DHCP Infrastructure • Dynamic Host Configuration Protocol (DHCP) • A simple, but critical, service • Functionality • Provides IP addressing information to client computers • Records the addresses leased • Can also be configured to notify DNS of address leases to update and maintain a Dynamic DNS (DDNS) zone
(Skill 1) Designing the DHCP Infrastructure (4) • Number of subnets supported in the design • Helps determine how many scopes are required • Identifies how many addresses will be provided via DHCP • Indicates how many superscopes are required • Identifies the exclusions and reservations that will be required
(Skill 1) Designing the DHCP Infrastructure (5) • RFC 1542 compliance in routers • To be RFC 1542-compliant, routers themselves must be capable of acting as Bootstrap Protocol (BOOTP) relay agents • Determines whether you require any DHCP relay agents to create a centralized DHCP design • Number of scopes required • Typically determined once you examine the subnet model
(Skill 1) Designing the DHCP Infrastructure (6) • Number of superscopes required • A superscope is a way of combining more than one non-contiguous IP address range into a single scope • Superscopes are only required when you need multiple non-contiguous subnets to be leased to a single physical subnet
(Skill 1) Designing the DHCP Infrastructure (7) • Reservations and exclusions • Reservations are typically used when you do not want to manually configure each client, but you want a specific group of clients to always have the same IP address • Exclusions are addresses that will never be handed out by the DHCP server
(Skill 1) Designing the DHCP Infrastructure (8) • Presence of other DHCP servers/Active Directory integration • Active Directory server authorization • Windows Server 2003 and Windows 2000 Server require DCHP servers to be authorized in Active Directory before starting, which is a mechanism to disable rogue DHCP servers • Windows NT, Unix, and NetWare DHCP servers, as well as client systems with Internet Connection Sharing enabled, do not have this feature • It is important to know where the other devices are on the network that may potentially function as a DHCP and make sure that they are not configured to offer IP addresses
(Skill 1) Designing the DHCP Infrastructure (9) • Redundancy requirements • Generally want at least two DHCP servers hosting each scope • Servers do not have to be solely dedicated to DHCP • DHCP can be installed on file servers, print servers, and even domain controllers
(Skill 1) Designing the DHCP Infrastructure (10) • Two basic types of DHCP infrastructure designs • Centralized • Decentralized
(Skill 1) Designing the DHCP Infrastructure (11) • Centralized design • Place two or more DHCP servers in a central hub location and enable BOOTP forwarding on routers for remote DHCP-enabled subnets • Typically easier to administer and less costly • May make meeting redundancy requirements difficult
(Skill 1) Designing the DHCP Infrastructure (12) • Decentralized design • Place a DHCP server on each DHCP-enabled subnet, with a backup copy of each different scope on an adjacent server • Requires more administrative resources • Requires more server resources • Makes achieving redundancy much easier
(Skill 1) Figure 5-4 Reservations and exclusions
(Skill 1) Figure 5-5 Decentralized DHCP model
(Skill 1) Figure 5-6 Centralized DHCP model
(Skill 2) Designing the Remote Access Infrastructure • Remote access infrastructure design considerations • Type of remote access (dial-up or VPN) required • How many concurrent users must be supported • Availability requirements
(Skill 2) Designing the Remote Access Infrastructure (2) • Type of remote access (dial-up or VPN) required • Determines the physical considerations of the design • Dial-up (POTS or ISDN) must ensure there are enough incoming lines • VPN • Ensure you have adequate Internet bandwidth • Ensure the encryption load can be supported
(Skill 2) Designing the Remote Access Infrastructure (3) • Availability requirements • Determines the number of RAS servers required • Determines the configuration of RAS servers • If using VPNs, can use network load balancing (NLB) for maximal availability • If using dial-up, specialized hardware to distribute connections is typically required
(Skill 2) Designing the Remote Access Infrastructure (4) • Hardware requirements • RAS is a fairly low-impact service • Network connectivity for RAS server is biggest consideration • When using VPNs, make sure server’s processing capability can support the encryption requirements of the connections
(Skill 2) Designing the Remote Access Infrastructure (5) • Server placement • Place RAS server and RAS connectivity as near as possible to the network resources that remote users will most commonly access • Placement of servers vis-à-vis the firewall is very important
(Skill 2) Designing the Remote Access Infrastructure (6) • Authentication, authorization, and accounting (AAA) • RADIUS is generally a better choice than Windows Accounting • Provides centralization of remote access policies and accounting information
(Skill 2) Designing the Remote Access Infrastructure (7) • Auditing and logging options • Enable Internet Authentication Service (IAS) logging to keep a running list of connections made to RAS server • Enable logging of accounting and authentication requests • Audit successful and failed account logon events
(Skill 2) Figure 5-10 Placement of a VPN server
(Skill 3) Designing Remote Access Policies (2) • Remote access policy conditions • Used to match a specific policy to a given user • Available condition components • Authentication-Type: Matches users based on the type of authentication protocol they are using • Called-Station-ID: Matches users based on the phone number they dialed • Calling-Station-ID: Matches users based on the phone number from which they are calling
(Skill 3) Designing Remote Access Policies (3) • Available condition components • Client-Friendly-Name: Defines the friendly name of the RADIUS client that is requesting use of the RADIUS server • Client-IP-Address: Matches the IP address of RADIUS client that is requesting access • Client-Vendor: Matches the vendor of the RADIUS client • Day-and-Time-Restrictions: Matches the user based on the day and time they attempt to connect
(Skill 3) Designing Remote Access Policies (6) • Remote access policy permissions • Used to control access • Set to allow or deny access • Remote access policy profile • Used to restrict which remote access settings are supported • Settings are defined in the Edit Dial-in Profile dialog box
(Skill 3) Designing Remote Access Policies (7) • Tabs in the Edit Dial-in Profile dialog box • Dial-in Constraints tab: Used to define any needed restrictions for the dial-in properties of the policy • IP tab: Used to define the IP properties associated with the connections to which this profile applies • Multilink tab: Used to define the setting applied to multilink connections for this policy
(Skill 3) Designing Remote Access Policies (8) • Tabs in the Edit Dial-in Profile dialog box • Authentication tab: Used to define the authentication methods allowed by this policy • Encryption tab: Used to define MPPE encryption levels for the connection • Advanced tab: Used to define special settings to be returned from RADIUS servers to RADIUS clients
(Skill 3) Figure 5-11 Components of a remote access policy
(Skill 3) Figure 5-12 Dial-in Constraints tab
(Skill 3) Figure 5-13 IP tab
(Skill 3) Figure 5-14 Multilink tab
(Skill 3) Figure 5-15 Authentication tab
(Skill 3) Figure 5-16 Encryption tab
(Skill 3) Figure 5-17 Advanced tab