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Chapter 11. Routing. Objectives. Configure Windows Server 2003 as a router Create and configure demand-dial connections for routing Configure Network Address Translation (NAT) for Internet connectivity Install Internet Connection Sharing (ICS) Configure Internet Connection Firewall (ICF).
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Chapter 11 Routing
Objectives • Configure Windows Server 2003 as a router • Create and configure demand-dial connections for routing • Configure Network Address Translation (NAT) for Internet connectivity • Install Internet Connection Sharing (ICS) • Configure Internet Connection Firewall (ICF)
Router Installation and Configuration • Windows Server 2003 • Can be used as a router • Can perform routing for TCP/IP and AppleTalk • Does not support IPX/SPX for routing • Implementing Windows Server 2003 as a router • Main benefit is cost • Server must be connected to at least two networks
Router Installation and Configuration (Continued) • Internet Security and Acceleration Server (ISA) • Provides proxy services • Routing and Remote Access snap-in • Used to add routing
Routing Tables • Routers • Make decisions about how to move packets from one network to another in the fastest way possible • Routing table • List of networks that are known to the router • Each entry contains • IP address of the network • Subnet mask of the network • Gateway used to reach the network • Router interface used to reach the gateway • Metric that measures how far away the network is
Routing Tables (Continued) • ROUTE PRINT command • Used to view routing table • Static routing • Entries that are added manually • Used when security is required • Addition of new network means routing table of each server must be changed • Introduction of error each time a change is made
Routing Tables (Continued) • Dynamic routing • Entries that are added automatically based on a routing protocol • Routers talk to each other to build their routing tables
Routing Protocols • Responsible for • Calculating best path from one network to another • Advertising routes for dynamic routing • Routing Information Protocol (RIP) • No configuration necessary under most circumstances • Hops • Number of routers through which the data must pass • Distance-vector routing • Path with the least number of hops
Routing Protocols (Continued) • Does not differentiate between different link speeds • Each RIP router sends broadcast packet every 30 seconds • Open Shortest Path First (OSPF) • Determines the best path from one network to another based on cost • Not normally implemented on Windows routers • Each interface on a router is assigned a cost
Routing Protocols (Continued) • Routing table • Builds a picture of the entire network • When communicating with other routers • Only sends changes in its routing table • Changes sent only when they occur, not every 30 seconds
Configuring RIP • RIP properties • Can configure type of events to be logged • Can configure IP addresses from which router accepts updates • General tab • Periodic update mode removes entries from routing table if router that advertised them is disabled or unreachable • Auto static update mode adds RIP learned routes to the routing table as static entries
Configuring RIP (Continued) • RIP routers • Advertise routes learnt from other routers then increment number of hops by 1 • RIP properties • Security tab • Allows you to configure which incoming and outgoing routes are accepted on this interface • Neighbors tab • Used only if broadcasts and multicasts are limited on the network
Configuring RIP (Continued) • Advanced tab • Can adjust how often routing table announcements are sent • Can adjust how long entries in the routing table last before they expire • Can adjust how long after they expire before they are removed from the routing table • Split-horizon processing and poison-reverse processing • Used to prevent routing loops in the case of a router failure
Demand-Dial Connections • Used to establish a connection between two routers when there is data to be sent • Demand-dial connections • Used to minimize the amount of phone time used on dial-up connections between routers • Can be used to initiate VPN connections between Windows routers • Can be created for Point-to-Point Protocol over Ethernet (PPPoE) connections • PPPoE • Used by many high-speed Internet providers to control access to their network • Authentication requires username and password
Creating Demand-dial Connections • For demand-dial connection to function properly • Server must be enabled to perform demand-dial routing • Port must be configured to allow demand-dial routing • Demand-dial interface must be created • Demand-dial Interface Wizard • Creates demand-dial connections
Demand-dial Interface Properties • Can be used to configure • Security settings • Idle timeout • Options tab • If “Persistent connection” option is chosen, servers are connected whenever RRAS is functional • If “Demand dial” option chosen, you can set an idle timeout • Security tab • Provides standard security options available on a VPN connection
Dial-out Hours • Controls when a demand-dial connection can be active • Typical configuration of dial-out hours • Allows a connection every few hours • Data is moved from one network to another in batches every few hours • If users are expected to access resources using the demand-dial connection at all times • Dial-out hours should be left at the default of 24 hours per day, seven days per week
Demand-dial Filters • Used to reduce amount of time a demand-dial connection is active • Control which types of network traffic trigger a demand-dial connection • Configuration is similar to a firewall rule • Can initiate a demand-dial connection • For specific traffic • For all traffic except that specified by a rule
Network Address Translation (NAT) • Uses a single Internet IP address to provide Internet access to all client computers • Included with Windows Server 2003 • Address ranges reserved for internal use • 10.0.0.0 through 10.255.255.255 • 172.16.0.0 through 172.31.255.255 • 192.168.0.0 through 192.168.255.255
Network Address Translation (Continued) • Proxy server • If implemented, clients must be configured to use the proxy server • Provides caching to speed up Internet connectivity • Most implementations are FTP aware and translate FTP packets properly
How NAT Works • Modifies IP headers of packets that are forwarded through a router • Builds a table to keep track of translations • Table lists • Original source IP address • Original source port number • New source port number • New source IP address • Always the external interface on the router • Does not need to be included in the table
Installing NAT • NAT protocol • Automatically installed when RRAS is configured to be a router • NAT Interface properties • For proper NAT functionality • One interface must be configured as a public interface • At least one interface must be configured as private interface • Basic firewall • Allows you to configure static packet filters
Installing NAT (Continued) • Services and Ports tab • Allows you to host services behind NAT but still allow access from Internet • ICMP tab • Dictates the types of ICMP packets the interface responds to • Address Pool tab • Defines a range of IP addresses that are handed out to client computers
Configuring NAT • NAT/Basic Firewall – Properties • General tab • Controls the level of logging that is performed • Translation tab • Configures how long mappingsare kept in the NAT table • Address Assignment tab • Can configure NAT to act as a DHCP server • Name Resolution tab • Configures the NAT router to act as a DNS proxy • Settings on this tab need not be enabled if internal DNS servers exist
Internet Connection Sharing (ICS) • Provides automated way for a small office to connect to the Internet using Windows Server 2003 as a router • Automatically performs NAT • Configures network connections • Because NAT is used, server must have at least two network cards • Configuration used by ICS cannot be changed
Internet Connection Sharing (Continued) • The following changes are made • Internal network connection is configured with • IP address 192.168.0.1 • Subnet mask 255.255.255.0 • Autodial enabled for dial-up/VPN/PPPOE connections • Static route for default gateway enabled when dial-up/VPN/PPPOE connection is activated • The ICS service is started • DHCP allocator is configured to distribute IP addresses from 192.168.0.2 to 192.168.0.254 • The DNS proxy is enabled
Internet Connection Sharing (Continued) • ICS server can only have one internal IP address • Network bridging • Allows interfaces to share a single IP address • Bridge • Controls network traffic based on MAC addresses • Allows computers on two different physical network segments to be on the same IP network • When network bridging is enabled • Choose multiple network cards in a server to act as a single IP network
Internet Connection Firewall • A stateful packet filter that can be used to protect any server running Windows Server 2003 • Stateful firewall • Requires only one rule for outbound traffic • Keeps track of TCP connections that are created by internal clients • Automatically allows response packets to return
Internet Connection Firewall (Continued) • Enabling ICF • ICF is configured per connection • If ICF enabled on a server that is not a router • Only that server is protected • If ICF enabled on a router • All computers on internal network are protected
Configuring ICF • When ICF is enabled • All packets addressed to server are dropped • Configuring services • Allows requests from the network to access services on the server running ICF • Services defined are the firewall rules for ICF