Date: Tue, 06 Apr 2004 14:24:09 +0200 From: Anders Lowinger <anders.lowinger@packetfront.com> To: Andre Oppermann <andre@freebsd.org> Cc: net@freebsd.org Subject: Re: do we support non contiguous netmasks ? Message-ID: <4072A169.9010206@packetfront.com> In-Reply-To: <40729B7A.2C984BD3@freebsd.org> References: <20040331005914.A6934@xorpc.icir.org> <40712A8F.9000704@packetfront.com> <40716208.808CF084@freebsd.org> <4072916D.101@packetfront.com> <40729B7A.2C984BD3@freebsd.org>
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Andre Oppermann wrote: >> interface ethernet 0 >> ip address 192.168.0.0 mask 255.255.253.0 > > This is simply a supernet (aka classless) but *not* a non-contignous > netmask. A non-contignous netmask would look like 255.254.255.0. Nope, 255.255.253.0 binary is 11111111.11111111.11111101.00000000 which is non-contignous. >> interface ethernet 0 >> ip address 192.168.0.0 mask 255.255.255.0 >> ip address 192.168.2.0 mask 255.255.255.0 secondary >> >>which gives the same functionality with contigious netmasks. > > Not really. Agree, not exactly the same > With the your second example hosts on the network have > to have different default gateways (192.168.0.1 and 192.168.2.1) > depending in which network range they are. In your first example > you just have one default gateway for all of them. However the > netmask has to match on all hosts otherwise you run into all sorts > of wierd trouble. In this case, the above is normally only used during a migration phase (as I mentioned, this is the only use of non-contignous i've seen, joining two separate subnets), so the hosts already have the correct default-route in their subnet. Hosts could optionally then be migrated to a common subnet. /Anders
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