Desired behaviour of "ifconfig -alias"

[Oliver Fromme]

Freddie Cash wrote:
 > For a set of IPs in the same subnet on the same interface, wouldn't the 
 > primary IP be the one with the proper netmask, and all IPs with netmasks 
 > of /32 be secondary?

That's historic.  :-)   Old versions of FreeBSD indeed
required the netmask of the "aliases" to be /32 in that
case.  But it's no longer the case.

# ifconfig re0
re0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=1b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING>
        inet 88.198.44.136 netmask 0xffffffe0 broadcast 88.198.44.159
        inet 88.198.173.154 netmask 0xfffffff8 broadcast 88.198.173.159
        inet 88.198.173.155 netmask 0xfffffff8 broadcast 88.198.173.159
        inet 88.198.173.156 netmask 0xfffffff8 broadcast 88.198.173.159
        inet 88.198.173.157 netmask 0xfffffff8 broadcast 88.198.173.159
        inet 88.198.173.158 netmask 0xfffffff8 broadcast 88.198.173.159

 > In that situation, wouldn't deleting the primary IP 
 > cause connection issues for the rest of the IPs?

No.  I can delete _any_ of the above IP addresses, and the
others would still work perfectly fine.  I already did
things like that (on a different machine).

As for outgoing connections:  It is true that the kernel
picks a random matching IP address to be the source IP,
which happens to be the first one, but that's just as
coincidence as "-alias" picking the first one if none
is given.  ;-)

Best regards
   Oliver

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