Cisco Cisco IOS Software Release 12.0(12) White Paper
amount of software defects and interoperability issues found in the network. Limited software versions also
reduce the risk of unexpected behavior with user interfaces, command or management output, upgrade
behavior and feature behavior. This makes the environment less complex and easier to support. Overall,
software version control improves network availability and helps lower reactive support costs.
reduce the risk of unexpected behavior with user interfaces, command or management output, upgrade
behavior and feature behavior. This makes the environment less complex and easier to support. Overall,
software version control improves network availability and helps lower reactive support costs.
Note: Similar network devices are defined as standard network devices with a common chassis providing a
common service.
common service.
Implement the following steps for software version control:
Determine device classifications based on chassis, stability, and new feature requirements.
•
Target individual software versions for similar devices.
•
Test, validate, and pilot chosen software versions.
•
Document successful versions as standard for similar−device classification.
•
Consistently deploy or upgrade all similar devices to standard software version.
•
IP Addressing Standards and Management
IP address management is the process of allocating, recycling and documenting IP addresses and subnets in a
network. IP addressing standards define subnet size, subnet assignment, network device assignments and
dynamic address assignments within a subnet range. Recommended IP address management standards reduce
the opportunity for overlapping or duplicate subnets, non−summarization in the network, duplicate IP address
device assignments, wasted IP address space, and unnecessary complexity.
network. IP addressing standards define subnet size, subnet assignment, network device assignments and
dynamic address assignments within a subnet range. Recommended IP address management standards reduce
the opportunity for overlapping or duplicate subnets, non−summarization in the network, duplicate IP address
device assignments, wasted IP address space, and unnecessary complexity.
The first step to successful IP address management is understanding the IP address blocks used in the
network. In many cases, network organizations have to rely on RFC 1918
network. In many cases, network organizations have to rely on RFC 1918
address space, which isn't
Internet addressable, but can be used to access the network in conjunction with Network Address Translation
(NAT). Once you have defined the address blocks, allocate them to areas of the network in a way that
promotes summarization. In many cases, you'll have to further subdivide these blocks based on the number
and size of subnets within the defined range. You should define standard subnet sizes for standard
applications, such as building subnet sizes, WAN link subnet sizes, loopback subnet size, or WAN site subnet
size. You can then allocate subnets for new applications out of a subnet block within a larger summary block.
(NAT). Once you have defined the address blocks, allocate them to areas of the network in a way that
promotes summarization. In many cases, you'll have to further subdivide these blocks based on the number
and size of subnets within the defined range. You should define standard subnet sizes for standard
applications, such as building subnet sizes, WAN link subnet sizes, loopback subnet size, or WAN site subnet
size. You can then allocate subnets for new applications out of a subnet block within a larger summary block.
For example, let's take a large enterprise network with an east coast campus, a west coast campus, a domestic
WAN, a European WAN, and other major international sites. The organization allocates contiguous IP
classless interdomain routing (CIDR) blocks to each of these areas to promote IP summarization. The
organization then defines the subnet sizes within those blocks and allocates sub−sections of each block to a
particular IP subnet size. Each major block or the entire IP address space can be documented in a spreadsheet
showing allocated, used, and available subnets for each available subnet size within the block.
WAN, a European WAN, and other major international sites. The organization allocates contiguous IP
classless interdomain routing (CIDR) blocks to each of these areas to promote IP summarization. The
organization then defines the subnet sizes within those blocks and allocates sub−sections of each block to a
particular IP subnet size. Each major block or the entire IP address space can be documented in a spreadsheet
showing allocated, used, and available subnets for each available subnet size within the block.
The next step is to create standards for IP address assignments within each subnet range. Routers and Hot
Standby Router Protocol (HSRP) virtual addresses within a subnet might be assigned the first available
addresses within the range. Switches and gateways may be assigned the next available addresses, followed by
other fixed address assignments, and finally dynamic addresses for DHCP. For example, all user subnets may
be /24 subnets with 253 available address assignments. The routers may be assigned the .1 and .2 addresses,
and the HSRP address assigned the .3 address, switches .5 through .9, and the DHCP range from .10 through
.253. Whatever standards you develop, they should be documented and referenced on all network engineering
plan documents to help ensure consistent deployment.
Standby Router Protocol (HSRP) virtual addresses within a subnet might be assigned the first available
addresses within the range. Switches and gateways may be assigned the next available addresses, followed by
other fixed address assignments, and finally dynamic addresses for DHCP. For example, all user subnets may
be /24 subnets with 253 available address assignments. The routers may be assigned the .1 and .2 addresses,
and the HSRP address assigned the .3 address, switches .5 through .9, and the DHCP range from .10 through
.253. Whatever standards you develop, they should be documented and referenced on all network engineering
plan documents to help ensure consistent deployment.
Naming Conventions and DNS/DHCP Assignments
Consistent, structured use of naming conventions and DNS for devices helps you manage the network in the
following ways:
following ways: