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