25 Feb
2012
25 Feb
'12
6:22 a.m.
Hello Marius,
Am 25. Feb 2012, um 11:10:56 schrieb Marius Petrescu:
Hello,
It is one thing I don't really get about this rollover...
A subnet is supposed to be a broadcast domain, so every subnet, don't matter
how small needs a network and a broadcast address to work properly.
That depends on
if your network is a broadcast network (like Ethernet).
Thats when you need the broadcast address.
Please note that the broadcast address is generally used only locally;
directed-broadcast ("ping 192.168.100.255") whith said network being
remote has been mostly disabled on the internet, because it was used
as an attack tool.
/31 is a valid netmask for Point-to-Point links where no broadcast is
necessary (see RFC 3021)
Classless approaches eliminate this and allow the use
of all subnets created
by subnetting (and I think all modern routers and OSes support this).
You can assume classless by default. Its been used for ages that way.
Any end-node supporting explicit netmask specification supports
classless, making this only an issue if you are concerned about dynamic
routing protocols, and there, only very archaic ones (RIP-1) dont deal
with classless networks.
This means that the roll over on the subnet boundary
would have to be e.g.
44.x.x.254 -> 44.x.x+1.1 or the routers on the subnet gateway may go havoc.
That depends: If you can change the netmask of the subnet in question to
a /23, then the routers would be fine. If you dont do that, then you
really run two separate IP networks (/24's in this case) on the same
physical wire, so yes, you will have to spend the all-zeroes host, the
all-ones-host and an additional IP for the gateway in this segment.
Best regards,
Mario
--
Mario Lorenz Internet: <ml(a)vdazone.org>
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