single host netmask (255.255.255.255)

[Petr Laznovsky]

My question is:

Is single host netmask allowed on ethernet interface in Windows 2000? I
need to assign IP 10.1.1.1 with netmask 255.255.255.255 to ETH
interface, but i`v got following error message: "Invalid IP or subnet
mask address". As I remember, dial-up DHCP requested address come
normally with this mask..... Wha is wrong??????

L.

 

[J.H]

255.255.255.255 is netmask broadcasting address.

What is wrong? because you do not know very well of TCP/IP basic knowledge.

Please learn the basic of TCP/IP before you want to tweak around with your
TCP/IP setting!!!

good luck,
J.H

 

[David D]

My question is:

Is single host netmask allowed on ethernet interface in Windows 2000? I
need to assign IP 10.1.1.1 with netmask 255.255.255.255 to ETH
interface, but i`v got following error message: "Invalid IP or subnet
mask address". As I remember, dial-up DHCP requested address come
normally with this mask..... Wha is wrong??????

L.

I think you remember wrong, fresch up your you basic tcp/ip knowledge.

The smallest usable net consists of 4 adresses (netmask 255.255.255.252)

First adress (host part all zero) is the net address.
Then come two addresses for hosts, you use on for your host and one for the default gateway (you want to talk to someone aren't you ?)
Last address is the broadcast address.

/David

 

[Neteng]

That's called a host route, not a broadcast address. A broadcast address is
the last address of a network. A broadcast is when the address is
255.255.255.255, not just the subnet mask. If he was to assign his NIC the
IP address of 255.255.255.255 then you can berate him. Maybe you're the one
who should be brushing up on TCP/IP skills.

Petr-
I don't believe Windows supports host routes on a physical NIC, you'll have
to use a loopback.

 

[Petr Laznovsky]

Dear Neteng,

If he was to assign his NIC the
IP address of 255.255.255.255 then you can berate him. Maybe you're the one
who should be brushing up on TCP/IP skills.

thank for your support

Petr-
I don't believe Windows supports host routes on a physical NIC, you'll have
to use a loopback.

Yes, exactly I need this address assign to loopback, but I have got same
error message. I need this "external loopback" to OSPF propagate into
our network. It is strange because, as I wrote, when you are use dial-up
internet connection, you probably got IP address with single host
netmask 255.255.255.255, I am also able to add single host with this
mask into routing table, but I am not able to assign this mask to the
interface :-(

But in the MS web seem to MS accept single host netmask:

 

[Petr Laznovsky]

I think you remember wrong, fresch up your you basic tcp/ip knowledge.

The smallest usable net consists of 4 adresses (netmask 255.255.255.252)

First adress (host part all zero) is the net address.
Then come two addresses for hosts, you use on for your host and one for
the default gateway (you want to talk to someone aren't you ?)
Last address is the broadcast address.

/David

David, please read Neteng`s answer to my question.

P.L.

 

[David D]

From RFC919

<snip>
The address 255.255.255.255 denotes a broadcast on a local hardware
network, which must not be forwarded. This address may be used, for
example, by hosts that do not know their network number and are
asking some server for it.

Thus, a host on net 36, for example, may:

- broadcast to all of its immediate neighbors by using
255.255.255.255

- broadcast to all of net 36 by using 36.255.255.255

(Note that unless the network has been broken up into subnets, these
two methods have identical effects.)

If the use of "all ones" in a field of an IP address means
"broadcast", using "all zeros" could be viewed as meaning
"unspecified". There is probably no reason for such addresses to
appear anywhere but as the source address of an ICMP Information
Request datagram. However, as a notational convention, we refer to
networks (as opposed to hosts) by using addresses with zero fields.
For example, 36.0.0.0 means "network number 36" while 36.255.255.255
means "all hosts on network number 36".
</snip>

 

[Petr Laznovsky]

David,

we are talking about __MASK__ 255.255.255.255, not the broadcast address!!!

P.L.

 

[David D]

I know. but Netengs post you referred to was also talking about broadcast address.

I can't imagine why you would want to assign a 255.255.255.255 mask to an ethernet interface as you then can't talk to someone (se my drevious post)

/D

 

[Petr Laznovsky]

I know. but Netengs post you referred to was also talking about
broadcast address.

Please, read Neteng`s post carefully, we are talking about HOST ROUTING.

I can't imagine why you would want to assign a 255.255.255.255 mask to
an ethernet interface as you then can't talk to someone (se my drevious
post)

It is simple: Imagine, you have router with three interfaces, you are
use dynamic routing OSPF protocol. The routes from three interfaces,
propagate via OSPF to the rest of network.... You wanna to manage this
router remotely, in case the some interface(s) are down.... One way is
to remember IP addresses assigned to each interfaces, but more smart
solution is to assign to this machine one EXTERNAL LOOPBACK address
(single IP with mask 255.255.255.255, in other words SINGLE HOST
assigned to Microsoft loopback adapter), and propagate this address (in
other words: SINGLE HOST NETWORK) to OSPF. Than you can access this
machine by this one IP address, does not care which interfaces are up or
down. In the UNIX word, usual thing......

P.L.

BTW: sorry for my horrible english, but I think yo can understand what I
mean....