mirror of
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[#496,!483] Updated ARM section about selectors usage with shared networks.
This commit is contained in:
Marcin Siodelski
committed by
Tomek Mrugalski
Tomek Mrugalski
parent
dba2986c42
commit
1335e5643c
@@ -4460,16 +4460,41 @@ log-servers value of 1.2.3.4, and routers set to 192.0.2.1.
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Local and Relayed Traffic in Shared Networks
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--------------------------------------------
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It is possible to specify an interface name in the shared network scope
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It is possible to specify an interface name at the shared network level
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to tell the server that this specific shared network is reachable
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directly (not via relays) using a local network interface. It is
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sufficient to specify it once at the shared network level. As all
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directly (not via relays) using the local network interface. As all
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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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using subnets that are reachable over different interfaces. It is
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possible to specify the interface parameter on each subnet, although its
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value must be the same for each subnet. Thus it is usually more
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convenient to specify it once at the shared network level.
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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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of the "interface" parameter. The following configuration is wrong.
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::
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"shared-networks": [
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{
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"name": "office-floor-2",
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"subnet4": [
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{
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"subnet": "10.0.0.0/8",
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"pools": [ { "pool": "10.0.0.1 - 10.0.0.99" } ],
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"interface": "eth0"
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},
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{
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"subnet": "192.0.2.0/24",
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"pools": [ { "pool": "192.0.2.100 - 192.0.2.199" } ],
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# Specifying the different interface name is a configuration
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# error. This value should rather be "eth0" or the interface
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# name in the other subnet should be "eth1".
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"interface": "eth1"
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}
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]
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} ]
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To minimize the chance of the configuration errors, it is often more convenient
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to simply specify the interface name once, at the shared network level, like
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shown in the example below.
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::
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@@ -4485,33 +4510,29 @@ convenient to specify it once at the shared network level.
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{
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"subnet": "10.0.0.0/8",
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"pools": [ { "pool": "10.0.0.1 - 10.0.0.99" } ],
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"interface": "eth0"
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},
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{
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"subnet": "192.0.2.0/24",
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"pools": [ { "pool": "192.0.2.100 - 192.0.2.199" } ]
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# Specifying a different interface name is a configuration
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# error:
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# "interface": "eth1"
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}
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]
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} ]
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Somewhat similar to interface names, relay IP addresses can also be
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specified for the whole shared network. However, depending on the relay
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configuration, it may use different IP addresses depending on which
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subnet is being used. Thus there is no requirement to use the same IP
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relay address for each subnet. Here's an example:
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In case of the relayed traffic, the subnets are typically selected using
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the relay agents' addresses. If the subnets are used independently (not
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grouped within a shared network) it is allowed to specify different relay
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address for each of these subnets. When multiple subnets belong to a
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shared network they must be selected via the same relay address and,
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similarly to the case of the local traffic described above, it is a
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configuration error to specify different relay addresses for the respective
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subnets in the shared network. The following configuration is wrong.
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::
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"shared-networks": [
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{
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"name": "kakapo",
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"relay": {
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"ip-addresses": [ "192.3.5.6" ]
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},
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"subnet4": [
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{
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"subnet": "192.0.2.0/26",
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@@ -4523,6 +4544,10 @@ relay address for each subnet. Here's an example:
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{
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"subnet": "10.0.0.0/24",
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"relay": {
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# Specifying a different relay address for this
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# subnet is a configuration error. In this case
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# it should be 192.1.1.1 or the relay address
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# in the previous subnet should be 192.2.2.2.
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"ip-addresses": [ "192.2.2.2" ]
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},
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"pools": [ { "pool": "10.0.0.16 - 10.0.0.16" } ]
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@@ -4531,12 +4556,45 @@ relay address for each subnet. Here's an example:
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}
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]
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In this particular case the relay IP address specified at the network
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level doesn't make much sense, as it is overridden in both subnets, but
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it was left there as an example of how one could be defined at the
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network level. Note that the relay agent IP address typically belongs to
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the subnet it relays packets from, but this is not a strict requirement.
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Kea accepts any value here as long as it is a valid IPv4 address.
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Again, it is better to specify the relay address at the shared network
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level and this value will be inherited by all subnets belonging to the
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shared network.
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::
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"shared-networks": [
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{
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"name": "kakapo",
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"relay": {
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# This relay address is inherited by both subnets.
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"ip-addresses": [ "192.1.1.1" ]
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},
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"subnet4": [
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{
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"subnet": "192.0.2.0/26",
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"pools": [ { "pool": "192.0.2.63 - 192.0.2.63" } ]
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},
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{
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"subnet": "10.0.0.0/24",
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"pools": [ { "pool": "10.0.0.16 - 10.0.0.16" } ]
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}
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]
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}
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]
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Even though it is technically possible to configure two (or more) subnets
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within the shared network to use different relay addresses, this will almost
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always lead to a different behavior than what the user would expect. In this
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case, the Kea server will initially select one of the subnets by matching
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the relay address in the client's packet with the subnet's conifguration.
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However, it MAY end up using the other subnet (even though it does not match
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the relay address) if the client already has a lease in this subnet, has a
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host reservation in this subnet or simply the initially selected subnet has no
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more addresses available. Therefore, it is strongly recommended to always
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specify subnet selectors (interface or a relay address) at 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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specify them at the subnet level and it may lead to the configurtion errors
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described above.
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Client Classification in Shared Networks
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----------------------------------------
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@@ -3959,16 +3959,41 @@ However, care should be taken for each subnet to have the same value.
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Local and Relayed Traffic in Shared Networks
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--------------------------------------------
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It is possible to specify an interface name in the shared network scope
|
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It is possible to specify an interface name at the shared network level
|
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to tell the server that this specific shared network is reachable
|
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directly (not via relays) using a local network interface. It is
|
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sufficient to specify it once at the shared network level. As all
|
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directly (not via relays) using the local network interface. As all
|
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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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using subnets that are reachable over different interfaces. It is
|
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possible to specify the interface parameter on each subnet, although its
|
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value must be the same for each subnet. Thus it is usually more
|
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convenient to specify it once at the shared network level.
|
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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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of the "interface" parameter. The following configuration is wrong.
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::
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"shared-networks": [
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{
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"name": "office-floor-2",
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"subnet6": [
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{
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"subnet": "2001:db8::/64",
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"pools": [ { "pool": "2001:db8::1 - 2001:db8::ffff" } ],
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"interface": "eth0"
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},
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{
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"subnet": "3ffe:abcd::/64",
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"pools": [ { "pool": "3ffe:abcd::1 - 3ffe:abcd::ffff" } ],
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# Specifying the different interface name is a configuration
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# error. This value should rather be "eth0" or the interface
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# name in the other subnet should be "eth1".
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# "interface": "eth1"
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}
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],
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} ]
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To minimize the chance of the configuration errors, it is often more convenient
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to simply specify the interface name once, at the shared network level, like
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shown in the example below.
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::
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@@ -3984,33 +4009,29 @@ convenient to specify it once at the shared network level.
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{
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"subnet": "2001:db8::/64",
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"pools": [ { "pool": "2001:db8::1 - 2001:db8::ffff" } ],
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"interface": "eth0"
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},
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{
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"subnet": "3ffe:abcd::/64",
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"pools": [ { "pool": "3ffe:abcd::1 - 3ffe:abcd::ffff" } ]
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# Specifying a different interface name is a configuration
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# error:
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# "interface": "eth1"
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}
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],
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} ]
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Somewhat similar to interface names, relay IP addresses can also be
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specified for the whole shared network. However, depending on the relay
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configuration, it may use different IP addresses depending on which
|
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subnet is being used. Thus there is no requirement to use the same IP
|
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relay address for each subnet. Here's an example:
|
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|
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In case of the relayed traffic, the subnets are typically selected using
|
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the relay agents' addresses. If the subnets are used independently (not
|
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grouped within a shared network) it is allowed to specify different relay
|
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address for each of these subnets. When multiple subnets belong to a
|
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shared network they must be selected via the same relay address and,
|
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similarly to the case of the local traffic described above, it is a
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configuration error to specify different relay addresses for the respective
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subnets in the shared network. The following configuration is wrong.
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::
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"shared-networks": [
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{
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"name": "kakapo",
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"relay": {
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"ip-addresses": [ "2001:db8::abcd" ]
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},
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"subnet6": [
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{
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"subnet": "2001:db8::/64",
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@@ -4023,6 +4044,10 @@ relay address for each subnet. Here's an example:
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"subnet": "3ffe:abcd::/64",
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"pools": [ { "pool": "3ffe:abcd::1 - 3ffe:abcd::ffff" } ],
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"relay": {
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# Specifying a different relay address for this
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# subnet is a configuration error. In this case
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# it should be 2001:db8::1234 or the relay address
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# in the previous subnet should be 3ffe:abcd::cafe.
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"ip-addresses": [ "3ffe:abcd::cafe" ]
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}
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}
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@@ -4030,12 +4055,45 @@ relay address for each subnet. Here's an example:
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}
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]
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In this particular case the relay IP address specified at the network
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level doesn't make much sense, as it is overridden in both subnets, but
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it was left there as an example of how one could be defined at the
|
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network level. Note that the relay agent IP address typically belongs to
|
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the subnet it relays packets from, but this is not a strict requirement.
|
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Kea accepts any value here as long as it is a valid IPv6 address.
|
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Again, it is better to specify the relay address at the shared network
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level and this value will be inherited by all subnets belonging to the
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shared network.
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::
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"shared-networks": [
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{
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"name": "kakapo",
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"relay": {
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# This relay address is inherited by both subnets.
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"ip-addresses": [ "2001:db8::1234" ]
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},
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"subnet6": [
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{
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"subnet": "2001:db8::/64",
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"pools": [ { "pool": "2001:db8::1 - 2001:db8::ffff" } ]
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},
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{
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"subnet": "3ffe:abcd::/64",
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"pools": [ { "pool": "3ffe:abcd::1 - 3ffe:abcd::ffff" } ]
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}
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]
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}
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]
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Even though it is technically possible to configure two (or more) subnets
|
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within the shared network to use different relay addresses, this will almost
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always lead to a different behavior than what the user would expect. In this
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case, the Kea server will initially select one of the subnets by matching
|
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the relay address in the client's packet with the subnet's conifguration.
|
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However, it MAY end up using the other subnet (even though it does not match
|
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the relay address) if the client already has a lease in this subnet, has a
|
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host reservation in this subnet or simply the initially selected subnet has no
|
||||
more addresses available. Therefore, it is strongly recommended to always
|
||||
specify subnet selectors (interface or a relay address) at 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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specify them at the subnet level and it may lead to the configurtion errors
|
||||
described above.
|
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Client Classification in Shared Networks
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----------------------------------------
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