Revision 031d2db1 doc/design-network.rst

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bitfields, the length of the network size each:
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``reservations``


  		





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  This field holds all IP addresses reserved by Ganeti instances, as


  		





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  well as cluster IP addresses (node addresses + cluster master)


  		





  
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  This field holds all IP addresses reserved by Ganeti instances.


  		





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``external reservations``


  		





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  This field holds all IP addresses that are manually reserved by the


  		





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  administrator, because some other equipment is using them outside the


  		





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  scope of Ganeti.


  		





  
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  administrator (external gateway, IPs of external servers, etc) or


  		





  
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  automatically by ganeti (the network/broadcast addresses,


  		





  
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  Cluster IPs (node addresses + cluster master)). These IPs are excluded


  		





  
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  from the IP pool and cannot be assigned automatically by ganeti to


  		





  
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  instances (via ip=pool).


  		





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The bitfields are implemented using the python-bitarray package for


  		





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space efficiency and their binary value stored base64-encoded for JSON


  		





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compatibility. This approach gives relatively compact representations


  		





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even for large IPv4 networks (e.g. /20).


  		





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Ganeti-owned IP addresses (node + master IPs) are reserved automatically


  		





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if the cluster's data network itself is placed under pool management.


  		





  
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Cluster IP addresses (node + master IPs) are reserved automatically


  		





  
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as external if the cluster's data network itself is placed under


  		





  
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pool management.


  		





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Helper ConfigWriter methods provide free IP address generation and


  		





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reservation, using a TemporaryReservationManager.


  		





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We also introduce a new ``ip`` address value, ``constants.NIC_IP_POOL``,


  		





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that specifies that a given NIC's IP address should be obtained using


  		





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the IP address pool of the specified network. This value is only valid


  		





  
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the first available IP address inside the pool of the specified network.


  		





  
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(reservations OR external_reservations). This value is only valid


  		





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for NICs belonging to a network. A NIC's IP address can also be


  		





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specified manually, as long as it is contained in the network the NIC


  		





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is connected to.


  		





  
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is connected to. In case this IP is externally reserved, Ganeti will produce


  		





  
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an error which the user can override if explicitly requested. Of course


  		





  
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this IP will be reserved and will not be able to be assigned to another


  		





  
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instance.


  		





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Hooks


  		












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