Desired behaviour of "ifconfig -alias"
olli at lurza.secnetix.de
Tue Feb 13 18:37:25 UTC 2007
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
inet 220.127.116.11 netmask 0xffffffe0 broadcast 18.104.22.168
inet 22.214.171.124 netmask 0xfffffff8 broadcast 126.96.36.199
inet 188.8.131.52 netmask 0xfffffff8 broadcast 184.108.40.206
inet 220.127.116.11 netmask 0xfffffff8 broadcast 18.104.22.168
inet 22.214.171.124 netmask 0xfffffff8 broadcast 126.96.36.199
inet 188.8.131.52 netmask 0xfffffff8 broadcast 184.108.40.206
> 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. ;-)
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