Re: network problem (fwd)
On 10/6/21, David wrote:
> On Thu, 7 Oct 2021 at 10:53, <rhkramer@ > wrote:
>> On Wednesday, October 06, 2021 11:15:11 AM Brian wrote:
>> > On Wed 06 Oct 2021 at 14:09:23 +0200, Pierre Frenkiel wrote:
>>
>> > > netmask 255.255.255.0
>> > > gateway 192.168.1.1
>> >
>> > Just in passing: The line with netmask 255.255.255.0 can be deleted.
>> > It is a deprecated option, as is broadcast. See #912220.
>>
>> Does that mean 255.255.255.0 is the default netmask?
>
> The netmask has to be specified *somewhere*. My understanding
> is that either CIDR or 'netmask' is required to do that. Read
> about CIDR here:
> https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#CIDR_notation
>
> But others here are vastly more knowledgeable than I am about
> networks, so additions or corrections are welcome, as always :)
It's Classless Inter-domain Routing (CIDR) now and network masks are
no longer supported [1]. If you take a look at RFC-950 [2], there is
no requirement that the network and sub-network bits of an address be
contiguous. 252.252.252.252 was a perfectly valid mask and yields the
same number of host bits (8) as a 255.255.255.0 mask does.
Then along came CIDR and dis-contiguous network/subnet bits were prohibited.
Lee
[1] Specifically, _bitmasks_ are no longer supported. "network masks"
are now just another way of specifying the first however many bits of
an address that make up the network portion of an address - eg. /24
and 255.255.255.0 both specify the first 24 bits of an address
[2] https://datatracker.ietf.org/doc/html/rfc950#page-15
3. A Class C Network Case (illustrating non-contiguous subnet bits)
For this case, assume that the requesting host is on class C
network 192.1.127.0, has address 192.1.127.19, that there is a
gateway at 192.1.127.50, and that on network an 3-bit subnet field
is in use (01011000), that is, the address mask is 255.255.255.88.
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