Date: Mon, 22 Aug 2011 23:49:21 +0000 From: John <jwd@freebsd.org> To: FreeBSD Net <freebsd-net@freebsd.org> Subject: ifconfig -alias with duplicate netmasks work? Message-ID: <20110822234921.GA34843@FreeBSD.org>
next in thread | raw e-mail | index | archive | help
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 via the commands: ifconfig bce0 inet 10.24.99.127 netmask 0xffff0000 broadcast 10.24.255.255 ifconfig bce0 inet 10.24.99.128 netmask 0xffff0000 broadcast 10.24.255.255 alias ifconfig bce0 inet 10.24.99.126 netmask 0xffff0000 broadcast 10.24.255.255 alias The man page for ifconfig says one 'must' use a different netmask, typically 0xffffffff. However, everything still seems to work ok. Has something changed, is the manpage wrong, am I totally missing something? Thanks, John man ifconfig If the address is on the same subnet as the first network address for this interface, a non-conflicting netmask must be given. Usually 0xffffffff is most appropriate.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20110822234921.GA34843>