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[libvirt] need help: what should be supported?

I need some help/guidance as to what networking characteristics should be supported by libvirt. Mostly, I am asking what should be valid for a prefix.

For IPv4:

The prefix can theoretically range from 0 to 32. Typically, the values of 8, 16 or 24 is used. For an IP specification, should I be able to specify prefix=32 (netmask This is not a network specification but one for a specific guest-host ... but, what will the virtualization host have for the address on this interface?

Proposed: prefix (or equivalent netmask) must be
    8 < prefix < 29

For IPv6: Similar to IPv4 but the range is (theoretically) 0 to 128. However, DHCPv6 and RA will **ONLY** work for prefix=64 ... nothing greater and nothing less. For an network on an interface which is visible to the virtualization host, it must have an address for the host; therefore, prefix <127. I am not sure what an IP definition with prefix=0 means for a libvirt virtual network.

Proposed: Prefix=64 for DHCPv6 and/or RA support. For other network addresses (such as static route),
    7 < prefix <= 64.

Most IPv6 software does not appear to handle subnets where prefix > 64 except for prefix=128 for a specific host address.

That is not to say that prefix <64 prefix < 128 could not have a meaning and be useful. But, if supported, how should it be specified so that user problems are minimized ... or do we just support it and what happens is a user problem?

Comments?  Suggestions??


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