My understanding is that the netmask (255.255.255.0 as you put it) is only
to determine how much of the IP address is used for the subnet address. I'm
a newb with this as well, so please, someone correct me if i'm wrong. If
your IP is 192.168.1.10 and your netmask is 255.255.255.0, then only the
last 8 bits of your IP (the last .10) is usable for a specific host on the
network and the first 24 bits are used for the network address and subnet
address. In binary:
11111111.11111111.11111111.00000000
would be your netmask and only the trailing 0's can be used for a host
address. This could also be expressed as 192.168.1.0/24 using CIDR. Let me
try to give you another example:
if your IP range was 192.168.99.0 to 192.168.99.255 and netmask was
255.255.255.254 then, in binary, the netmask would look like this:
1111111.11111111.11111111.11100000
Being that you are using 192.168.99.0 as the network address, the first
three 1's in the last 8 bits of the netmask would be your subnet addresses.
So you could use.192.168.99.32, *.64, *.96, *.128, *.160 and *.192 for
subnet addresses and the IPs between all of those (except the last IP, so
you can only assign 30 per subnet since the last IP is used for broadcast)
can be assigned to hosts.
Hopefully that (correctly) clears up any confusion involving subnets and
netmasks. Like I said, I'm new at as well, so please correct me if I am
wrong.
----- Original Message -----
From: "Ulf Magnusson" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Friday, June 24, 2005 6:25 AM
Subject: Re: NAT router confusion
----- Original Message -----
From: "Michael H. Semcheski" <[EMAIL PROTECTED]>
Date: Friday, June 24, 2005 1:46 am
Subject: Re: NAT router confusion
On Thursday 23 June 2005 07:43 pm, Ulf Magnusson wrote:
> Is this router really some switch/router hybrid? Or..? Bleh, someone
> please sort this out for me. I realize this isn't strictly
> FreeBSD-related, but I simply couldn't think of a better place to
pick> brains, so I hope I'll be excused :)
It is a switch / router hybrid. If the traffic is going to an
address on the
same network, its a switch. If the traffic is going to an address
on a
different network, its a router.
If you understand that concept, then you should have a pretty good
idea of how
the system works.
I do not have a complete enough understanding of IP networks to
explain this
in specific detail. I think the key is that the computer
generating the
traffic looks at the netmask for the sending interface (eg,
255.255.255.0)
and uses this to determine if the endpoint of the traffic is on the
same
network or not. If it is, it sends the traffic directly to the
host. If it
is on a different network, it forwards the traffic to the gateway
address.
Mike
Thanks, I think I understand how it works now. I guess it's basically
like an ordinary router that pretends it's a switch for all addresses
that appear on the same local network. It looks at the destination
address in IP packets and the address of the sending system and goes
into switch mode if they both appear on the same subnet (which is pretty
much verbatim what you said, when I think about it).
I'll throw another short question in the mix while I'm at it.. perhaps I
should rename the thread "Switching/routing questions from a curious
networking newbie" :-)
Do switches gain anything by having full-duplex connections to hubs? I
understand there must be a performance benefit when you connect a host
directly to a switch, but won't the half-duplex connections of the hosts
to the hub become a bottleneck?
Ulf
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