Date: Tue, 06 Apr 2004 15:03:13 +0200 From: Andre Oppermann <andre@freebsd.org> To: Anders Lowinger <anders.lowinger@packetfront.com> Cc: net@freebsd.org Subject: Re: do we support non contiguous netmasks ? Message-ID: <4072AA91.DA00A9F3@freebsd.org> References: <20040331005914.A6934@xorpc.icir.org> <40712A8F.9000704@packetfront.com> <40716208.808CF084@freebsd.org> <4072916D.101@packetfront.com> <40729B7A.2C984BD3@freebsd.org> <4072A169.9010206@packetfront.com>
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Anders Lowinger wrote: > > 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. You are right. I was looking to quickly. However at least my Cisco doesn't like it: "Bad mask 0xFFFFFD00 for address", IOS 12.2(10). > > 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. Never heard of that (only supernets/subnets with respect to classful notation), never done it and at least my Cisco 7500 doesn't like it. So I doubt others have got their Cisco to like it. -- Andre
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