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[#2103] Additional text edits through line 5878
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committed by
Andrei Pavel
parent
dfe741e77e
commit
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@@ -5356,16 +5356,16 @@ DHCP servers use subnet information in two ways. It is used to
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both determine the point of attachment, i.e. where the client is
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both determine the point of attachment, i.e. where the client is
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connected to the network, and to
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connected to the network, and to
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group information pertaining to a specific location in the network.
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group information pertaining to a specific location in the network.
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However, it is sometimes useful to have more than one
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Sometimes it is useful to have more than one
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logical IP subnet deployed on the same physical link.
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logical IP subnet deployed on the same physical link.
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Understanding that two or more subnets are used on the same link requires
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Understanding that two or more subnets are used on the same link requires
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additional logic in the DHCP server. This capability is called "shared
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additional logic in the DHCP server. This capability is called "shared
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networks" in Kea, and sometimes also
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networks" in Kea, and sometimes also
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"shared subnets"; in Microsoft's nomenclature it is called "multinet."
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"shared subnets"; in Microsoft's nomenclature it is called "multinet."
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There are many use cases where the feature is useful; here we
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There are many cases where the shared networks feature is useful; here we
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explain just a handful of the most common ones. The first and by far
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explain just a handful of the most common ones. The first and by far
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most common use case is an existing network that has grown and is
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most common use case is an existing IPv4 network that has grown and is
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running out of available address space. Rather than migrating all
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running out of available address space. Rather than migrating all
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devices to a new, larger subnet, it is easier to simply configure
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devices to a new, larger subnet, it is easier to simply configure
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additional subnets on top of the existing one. Sometimes, due to address
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additional subnets on top of the existing one. Sometimes, due to address
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@@ -5402,7 +5402,7 @@ default.
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all the addresses from the first subnet in a shared network before
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all the addresses from the first subnet in a shared network before
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allocating addresses from other subnets.
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allocating addresses from other subnets.
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In order to define a shared network an additional configuration scope is
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To define a shared network, an additional configuration scope is
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introduced:
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introduced:
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::
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::
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@@ -5461,12 +5461,12 @@ of two or more subnets. However, for testing purposes, an empty subnet
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or a network with just a single subnet is allowed. This is not a
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or a network with just a single subnet is allowed. This is not a
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recommended practice in production networks, as the shared network logic
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recommended practice in production networks, as the shared network logic
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requires additional processing and thus lowers the server's performance.
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requires additional processing and thus lowers the server's performance.
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To avoid unnecessary performance degradation, the shared subnets should
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To avoid unnecessary performance degradation, shared subnets should
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only be defined when required by the deployment.
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only be defined when required by the deployment.
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Shared networks provide the ability to specify many parameters in the
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Shared networks provide the ability to specify many parameters in the
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shared network scope that apply to all subnets within it. If
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shared network scope that apply to all subnets within it. If
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necessary, it is possible to specify a parameter in the shared network scope and
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necessary, it is possible to specify a parameter in the shared-network scope and
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then override its value in the subnet scope. For example:
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then override its value in the subnet scope. For example:
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::
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::
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@@ -5541,7 +5541,7 @@ subnets in a shared network are expected to be used on the same physical
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link, it is a configuration error to attempt to define a shared network
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link, it is a configuration error to attempt to define a shared network
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using subnets that are reachable over different interfaces. In other
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using subnets that are reachable over different interfaces. In other
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words, all subnets within the shared network must have the same value
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words, all subnets within the shared network must have the same value
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of the ``interface`` parameter. The following configuration is an
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for the ``interface`` parameter. The following configuration is an
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example of what **NOT** to do:
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example of what **NOT** to do:
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::
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::
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@@ -5568,7 +5568,7 @@ example of what **NOT** to do:
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} ]
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} ]
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To minimize the chance of configuration errors, it is often more convenient
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To minimize the chance of configuration errors, it is often more convenient
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to simply specify the interface name once, at the shared network level, as
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to simply specify the interface name once, at the shared-network level, as
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shown in the example below.
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shown in the example below.
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::
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::
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@@ -5632,7 +5632,7 @@ of what **NOT** to do:
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}
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}
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]
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]
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Again, it is better to specify the relay address at the shared network
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Again, it is better to specify the relay address at the shared-network
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level; this value will be inherited by all subnets belonging to the
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level; this value will be inherited by all subnets belonging to the
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shared network.
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shared network.
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@@ -5669,7 +5669,7 @@ host reservation in this subnet, or simply if the initially selected subnet has
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more addresses available. Therefore, it is strongly recommended to always
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more addresses available. Therefore, it is strongly recommended to always
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specify subnet selectors (interface or relay address) at the shared-network
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specify subnet selectors (interface or relay address) at the shared-network
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level if the subnets belong to a shared network, as it is rarely useful to
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level if the subnets belong to a shared network, as it is rarely useful to
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specify them at the subnet level and it may lead to the configuration errors
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specify them at the subnet level and may lead to the configuration errors
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described above.
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described above.
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Client Classification in Shared Networks
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Client Classification in Shared Networks
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@@ -5687,7 +5687,7 @@ appropriate subnet is selected for a given client type.
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If a subnet is associated with a class, only the clients belonging to
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If a subnet is associated with a class, only the clients belonging to
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this class can use this subnet. If there are no classes specified for a
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this class can use this subnet. If there are no classes specified for a
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subnet, any client connected to a given shared network can use this
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subnet, any client connected to a given shared network can use this
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subnet. A common mistake is to assume that a subnet including a client
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subnet. A common mistake is to assume that a subnet that includes a client
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class is preferred over subnets without client classes. Consider the
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class is preferred over subnets without client classes. Consider the
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following example:
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following example:
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@@ -5725,7 +5725,7 @@ subnet 10.0.0.0/24 will be used (or preferred) for this client. The
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server can use either of the two subnets, because the subnet 192.0.2.0/26
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server can use either of the two subnets, because the subnet 192.0.2.0/26
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is also allowed for this client. The client classification used in this
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is also allowed for this client. The client classification used in this
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case should be perceived as a way to restrict access to certain subnets,
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case should be perceived as a way to restrict access to certain subnets,
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rather than a way to express subnet preference. For example, if the
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rather than as a way to express subnet preference. For example, if the
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client does not belong to the "b-devices" class, it may only use the
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client does not belong to the "b-devices" class, it may only use the
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subnet 192.0.2.0/26 and will never use the subnet 10.0.0.0/24.
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subnet 192.0.2.0/26 and will never use the subnet 10.0.0.0/24.
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@@ -5779,7 +5779,7 @@ be refused service. However, this may be a desired outcome if one wishes
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to provide service only to clients with known properties (e.g. only VoIP
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to provide service only to clients with known properties (e.g. only VoIP
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phones allowed on a given link).
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phones allowed on a given link).
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Note that it is possible to achieve an effect similar to the one
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It is possible to achieve an effect similar to the one
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presented in this section without the use of shared networks. If the
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presented in this section without the use of shared networks. If the
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subnets are placed in the global subnets scope, rather than in the
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subnets are placed in the global subnets scope, rather than in the
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shared network, the server will still use classification rules to pick
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shared network, the server will still use classification rules to pick
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