module 3: designing ip addressing. module overview designing an ipv4 addressing scheme designing...
TRANSCRIPT
Module 3:Designing IP Addressing
Module Overview
• Designing an IPv4 Addressing Scheme
• Designing DHCP Implementation
• Designing DHCP Configuration Options
• Designing an IPv6 Addressing Scheme
• Designing an IPv6 Transition
Lesson 1: Designing an IPv4 Addressing Scheme
• Considerations for Determining Hosts per Subnet
• Considerations for Determining Number of Subnets
• Guidelines for Designing IPv4 Addressing
Considerations for Determining Hosts per Subnet
When determining the number of hosts per subnet, consider:
• All devices on each subnet, including routers
• Network design specifications
• Router and switch performance
• Future growth
The 2n-2 method to determine host bits required for hosts
Considerations for Determining Number of Subnets
When determining the number of subnets, consider:
• WAN locations
Security zones within each location
• Capacity on each segment
• Future growth
The 2n method to determine the number of bits required for subnets
Guidelines for Designing IPv4 Addressing
Use classless routing protocols
Use variable-length subnetting to divide IP ranges
Use supernetting to combine IP ranges
Use public addresses only when a host needs to be connected directly to the Internet
Use classless IP addressing
Use private addresses if you use an indirect connection to the Internet, such as a proxy server or NAT
Lesson 2: Designing DHCP Infrastructure
• Options for Automatic IP Address Assignment
• DHCP Communication Process
• Design Options for DHCP Server
• Methods for Improving DHCP Server Availability
• Securing DHCP Servers
• Guidelines for Designing DHCP Infrastructure
Options for Automatic IPv4 Address Assignment
Option Description
DHCP • IP address and configuration options are delivered by a DHCP server
APIPA• Generates a 169.254.x.x address when a DHCP
server cannot be contacted
• Not suitable for domains or Internet access
Alternate IP • Uses an alternate configuration with options
when a DHCP server cannot be contacted
• Useful for roaming users in some cases
DHCP Communication Process
• DHCP clients and servers communicate with broadcast messages
Broadcast messages by default do not cross routers
• By default, a DHCP server is required on each subnet
• Use DHCP relays to allow a centralized DHCP server to service DHCP clients
Methods for Improving DHCP Server Availability
Redundancy option Details
Split scope
• Divides DHCP scopes between multiple DHCP servers
• 80:20 rule: one DCHP server provides 80% of the address range; the second server provides 20%
Failover clustering
• Allows two or more physical servers to be managed as a single, logical server
• Clustering enables a local method of failover, which achieves greater fault tolerance
Standby server • Gets activated only when need arises
• Requires manual administration to ensure failover
Securing DHCP Servers
DHCP authorization:
Prevents unauthorized Windows servers from running the DHCP service
Does not stop rogue DHCP servers running other operating systems
Enterprise Administrators can authorize a DHCP server
Windows-based groups:
DHCP Administrators local group has permission to configure DHCP servers
Server Operators and Administrators can also configure DHCP servers
DHCP Users local group has permission to read DHCP server configuration
Guidelines for Designing DHCP Infrastructure
In virtualization scenarios, consider using the internal DHCP server
For a combined DHCP infrastructure, base DHCP server locations on the physical characteristics of the LAN or WAN infrastructure
Provide high availability for DHCP
Limit each DHCP server to 1,000 scopes
DHCP servers have low resource utilizationand are good candidates for virtualization
Lesson 3: Designing DHCP Configuration Options
• Using Superscopes in DHCP Infrastructure
• Using Reservations in DHCP Infrastructure
Superscopes in DHCP Infrastructure
Superscopes: Are used when two subnets are present on the same
physical segment
Configure the DHCP to recognize the two subnets as a single physical segment
Ensure that only one DHCP response is sent instead of one DHCP response for each subnet
Reduce DHCP-related network traffic
Using Reservations in DHCP Infrastructure
Reservations:
Link a specific IP address with a specific MAC address
Are an alternative to static IP addresses
Are easier to manage and modify than static IP addresses
Can be used for printers to hosts with associated firewall rules
Lesson 4: Designing an IPv6 Addressing Scheme
• Benefits of IPv6
• IPv6 Address Types
• Guidelines for Designing an IPv6 Addressing Scheme
Benefits of IPv6
Some benefits of IPv6 are:
Larger address space
Hierarchical design for routing efficiency
Includes support for IPsec
Includes support for Quality of Service
Stateful and stateless address configuration
New extensible header format that minimizes overhead
Neighbor Discovery replaces ARP broadcasts
IPv6 Address Types
Address Type Description
Global unicast Equivalent to public IPv4 addresses
Link-Local unicast Automatically assigned to each host for communication on the local subnet
Unique local unicast Equivalent to IPv4 private addresses
Site local unicast Similar to unique local but depreciated
Multicast Equivalent to IPv4 multicast with an additional scope option
Anycast A unicast address that has been assigned to multiple computers
Guidelines for Designing an IPv6 Addressing Scheme
Be aware that most older applications do not support IPv6
Use a hierarchical design for routing efficiency
Obtain a global unicast IPv6 address to communicate on the IPv6 Internet
Do not use the global ID of a unique local address for subnetting
Randomly generate the global ID of a unique local address
Use stateless autoconfiguration to simplify address assignment
Use DHCPv6 to assign additional configurationoptions such as DNS servers