[comp.protocols.tcp-ip] subnets

wmg@cbnewsk.ATT.COM (william.m.gilroy) (06/21/89)

I was wondering if anyone could explain (or show me where to
RTFM) on subnetting.  I have read the sun manuals on the subject
and it is still not clear.  What I am trying to do is have a 
server with two ethernets, but I do not want to route all 
the traffic on the main ethernet to the second ethernet.  
I don't understand how to set up the hosts file in relation
to the subnet mask.  Am I missing some simple?
I think subnets are just what I need.  If I am going about 
this all wrong, feel free to let me know.

Thanks,

Bill

William M. Gilroy - AT&T-BL Engineering Research Center
att!howard!wmg
(609) 639-2206  - CORNET 258
[ General disclaimer ]  - Nothing reserved except the right to send 
lawyers, guns, and money.

jacobson@cs.iastate.edu (Doug Jacobson) (10/23/90)

I have two general questions about subnetting in TCP/IP.

At Iowa State University we have a class B address and our
campus network consists of a four large bridged Ethernet segments
with a FDDI backbone used to connect these segments.  Some of the
segments contain IP Gateways.  The campus was using transparent subnetting
until about a month aao when the campus changed to unsubnetted.  The
Broadcast addresses and the Netmasks have been changed.
(Broadcast changed from 129.186.X.255 to 129.186.255.255 and the netmask
changed from 255.255.0.0 to 255.255.255.0).  The questions I are:

1)  Should we have changed the campus to not support transparent subnetting
even though we do have some true subnets within our domain.

2)  How do other organizations with class B addresses set up their networks
and do they use transparent subnetting.

You can mail your responses to me at doug@isuee1.ee.iastate.edu
if there is enough interest I will post the results to question 2.

haddad@hplred.HP.COM (R. Peter Haddad) (10/24/90)

/ hplred:comp.protocols.tcp-ip / jacobson@cs.iastate.edu (Doug Jacobson) /  2:19 pm  Oct 22, 1990 /

I have two general questions about subnetting in TCP/IP.

At Iowa State University we have a class B address and our
campus network consists of a four large bridged Ethernet segments
with a FDDI backbone used to connect these segments.  Some of the
segments contain IP Gateways.  The campus was using transparent subnetting
until about a month aao when the campus changed to unsubnetted.  The
Broadcast addresses and the Netmasks have been changed.
(Broadcast changed from 129.186.X.255 to 129.186.255.255 and the netmask
changed from 255.255.0.0 to 255.255.255.0).  The questions I are:

1)  Should we have changed the campus to not support transparent subnetting
even though we do have some true subnets within our domain.

2)  How do other organizations with class B addresses set up their networks
and do they use transparent subnetting.

You can mail your responses to me at doug@isuee1.ee.iastate.edu
if there is enough interest I will post the results to question 2.
----------

Doug :

Perhaps I am missing something here. Your broadcast address seems to have 
changed to accomodate a 0 length subnet field, therefore a 16 bit host field.
Your netmask however has been changed to allow an 8 bit subnet field, and
therefore an 8 bit host field. Am I misunderstanding the situation ?  What do
you mean by "transparent" subnetting ? 

Peter Haddad
HPLabs Network Eng.