© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Designing IP Addressing and Selecting Routing Protocols Designing IP Addressing

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Prerequisite Knowledge IPv4 address and mask structure IPv4 classes and CIDR Static addressing Dynamic addressing with DHCP DNS Private and public addresses NAT and PAT –Static NAT –Dynamic NAT –Overloading

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Private and Public IPv4 Address Guidelines

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Network Size and IP Addressing Planning How many locations are in the network? How many devices in each location? What are the IP addressing requirements for individual locations? What subnet size is appropriate?

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Determining General Network Topology

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IP Address Requirements by Location LocationTotal San FranciscoMain %1290 DenverRegional %441 HoustonRegional %329 Remote Office 1Remote %28 Remote Office 2Remote %35 Remote Office 3Remote %21 Total Office TypeWorkstationsServersIP PhonesRouterInterfacesSwitchesLayer 3Firewall andNet DeviceInterfacesReserve

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IP Addressing Hierarchy Reasons to implement include: Influence of IP addressing on routing Modular design and scalable solutions Support for route aggregation

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Route Summarization Groups Benefits of hierarchical addressing include: –Support for route summarization groups –Efficient aggregation of routing advertisements Poorly designed IP addressing results in: –Excess routing traffic, leading to additional bandwidth consumption –Increased routing table recalculations, degrading router performance

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Address Blocks by Location LocationCountsRounded Power of 2Address Block San Francisco Campus1290 Denver Region Denver Office 1441 Remote Office 128 Remote Office 235 Houston Region Houston Campus329 Remote Office 321

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Address Blocks by Location LocationCountsRounded Power of 2Address Block San Francisco Campus Denver Region Denver Office Remote Office Remote Office Houston Region Houston Campus Remote Office 32164

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Address Blocks by Location LocationCountsRounded Power of 2Address Block San Francisco Campus Denver Region1024 Denver Office Remote Office Remote Office Houston Region1024 Houston Campus Remote Office 32164

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Address Blocks by Location LocationCountsRounded Power of 2Address Block San Francisco Campus – /21 Denver Region – /22 Denver Office – /23 Remote Office /26 Remote Office /26 Houston Region – /22 Houston Campus – /23 Remote Office /26

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Hierarchical IP Addressing Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Hierarchical IP Addressing Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Managing IP Addresses Using DHCP in the enterprise. Using DNS in the enterprise. Using NAT in the enterprise.

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Recommended Practices for IP Address Assignment Method CriteriaStrategic Address AssignmentDynamic Address Assignment with DHCP Node typeInfrastructure devices such as routers and switches End-user devices Number of end user devicesUp to 30 end-user devicesMore than 30 end user devices RenumberingRequires manual reconfiguration of all hosts Only DHCP server reconfiguration is needed Address trackingEasy address trackingRequires additional DHCP server configuration Additional parametersManual configuration of all hosts required Only DHCP server needs to be configured High availabilityIP addresses are available at any time Redundant DHCP server is required Security concernsMinor security riskAny device gets IP address

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: IP Address Assignment Methods in an Enterprise Network

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Static vs. Dynamic Name Resolution Names used to ease computer-human interaction Names resolved to IP addresses Different name resolution strategies: –Static –Dynamic

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Recommended Practices for Name Resolution Method CriteriaStatic Name ResolutionDynamic Name Resolution Number of hostsUp to 30 hostsMore than 30 hosts Isolated networkApplicable Internet connectivityNot applicableMandatory Frequent changes and addition of names Not recommendedRecommended Application depending on name resolution Not recommendedRecommended

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Using DNS for Name Resolution

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Locating DHCP and DNS Servers in the Network

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv6 Address Structure x:x:x:x:x:x:x:x, where x is 16 bits, represented by a hexadecimal number: 2031:0000:130F:0000:0000:09C0:876A:130B Can be also written as 2031:0:130F::9C0:876A:130B

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Benefits of IPv6 Addressing Larger address space Globally unique IP addresses Site multihoming Header format efficiency Improved privacy and security Flow labeling capability Increased mobility and multicast capabilities

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv6 Address Scope Types IPv6 address scope types: –Unicast (one to one) –Anycast (one to nearest) –Multicast (one to many) Broadcast addresses not available

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv6 Address Types: Link-Local and Site-Local Link-Local Address Site-Local Address

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv6 Address Types: Global Aggregatable Global Aggregatable Address

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv6 Routing Protocol Considerations Interior Gateway Protocols (IGPs) for inside autonomous systems: –RIPng –EIGRP IPv6 –OSPFv3 –Integrated IS-IS Exterior gateway protocols (EGPs) for peering between autonomous systems: –BGP+

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv6 Address Assignment Strategies Static: Same as IPv4 Dynamic: Link-local Stateless Stateful using DHCPv6

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv6 Name Resolution Static: Same as IPv4 Dynamic (autoconfiguration): DNS server with IPv6 stack support

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv4- and IPv6-Aware Applications and Name Resolution In a dual-stack case, an application is IPv4- and IPv6-enabled. The application decides which stack to use and asks DNS for the address.

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v IPv4-to-IPv6 Transition Strategies Three major transition strategies are available: Dual stack (IPv4 and IPv6 coexist in the same device and networks) Tunneling (IPv6 packets are encapsulated into IPv4 packets) Translation (IPv6-only devices can talk to IPv4 devices)

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Dual-Stack Mechanism Both IPv4 and IPv6 stacks are enabled. Applications can talk to both stacks. IP version choice is based on name lookup and application preference. Popular operating systems support IPv6.

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Tunneling Mechanism Encapsulates the IPv6 packet in the IPv4 packet. Techniques: Manually configured Semiautomated Automatic

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Translation Mechanism

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Summary Key components of an IPv4 addressing scheme include IP address structure, address classes, subnetting, and masking. Well-designed hierarchical IP addressing enables efficient aggregation of routing advertisements, which consumes less bandwidth and router CPU. –Dynamic IP address assignment is a recommended practice in the enterprise. –Dynamic name resolution with a DNS server is a recommended practice in the enterprise. IPv6 was designed as a successor to IPv4 to overcome IPv4 limitations. –The IPv6 address structure and address types support a much larger address space than IPv4. –IPv6 supports two address types: link-local and global aggregatable.

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v