ifconfig -alias with duplicate netmasks work?

[Doug Barton]

On 08/22/2011 16:49, John wrote:
> Fellow Net'ers
> 
>    Debugging an nfs locking problem to a linux host, I accidently
> issued some ifconfig commands on the bsd server (9-current) and
> found that duplicate netmasks seem to work fine. For instance:
> 
> bce0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
> 	options=c01bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,VLAN_HWTSO,LINKSTATE>
> 	ether d4:85:64:66:2a:14
> 	inet6 fe80::d685:64ff:fe66:2a14%bce0 prefixlen 64 scopeid 0x1 
> 	inet 10.24.99.127 netmask 0xffff0000 broadcast 10.24.255.255
> 	inet 10.24.99.128 netmask 0xffff0000 broadcast 10.24.255.255
> 	inet 10.24.99.126 netmask 0xffff0000 broadcast 10.24.255.255
> 	nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
> 	media: Ethernet autoselect (1000baseT <full-duplex>)
> 	status: active

My experience on 8.x is that this will work for most things, but then
fail in odd ways. You're still better off following the old advice of
making the aliases for the same network have the all-1s netmask.


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