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RE: [FW1] Netmasks on different NIC's

To: karimi@ca.ibm.com
Subject: RE: [FW1] Netmasks on different NIC's
From: Carric Dooley <carric@com2usa.com>
Date: Tue, 5 Oct 1999 17:08:42 -0400 (EDT)
Cc: sirving@ca.ibm.com, fw-1-mailinglist@lists.us.checkpoint.com


OK... I guess we can dropt his argument... when I took Cisco Internetwork
Design, I was told by my instructor at the time that only BGP would do
supernetting under CIDR.  Apparently RIP2, OSPF2, and BGP4 all fully
sypport CIDR (and my guess is EIGRP does too).

I apologize for trying to spread my ignorance.  I suck.

On Tue, 5 Oct 1999, Carric Dooley wrote:

> 
> Self Correction.. CIDR is a broader term than this post implies(sorry)...
> it's more using /24 or /22 as the subnet mask, irregardless of class
> (since by definition it's classless).  VLSM is subnetting.. not
> supernetting.  CIDR is the vehicle facilitates supernetting. I do not
> think any other protocols (besides BGP4) are truly classless in this
> sense.
> 
> On Tue, 5 Oct 1999, Carric Dooley wrote:
> 
> > 
> > VLSM and CIDR ARE NOT THE SAME THING.  VLSM is subnetting subnets
> > essentially.  Eg.
> > 
> > I have 3 subnets 192.168.1.1/25 192.168.1.129/26 192.168.1.192/26
> > 
> > CIDR is going the other way:
> > 
> > I have 4 Class C networks:
> > 
> > 192.168.0/24
> > 192.168.1/24
> > 192.168.2/24
> > 192.168.3/24
> > (notice they are contiguous)
> > 
> > To shrink routing tables (under BGPv4) I can aggregate these networks
> > going back agains the natural mask:
> > 192.168.0/22
> > 
> > Now intead of 4 enteries in my router table I have 1.  This allows routers
> > to make decisions quicker.
> > 
> > On Tue, 5 Oct 1999 karimi@ca.ibm.com wrote:
> > 
> > > 
> > > 
> > > 
> > > 
> > > if it's a Solaris box (2.6/7.0) it supports VLSM (variable length subnet
> > > masking) so you should
> > > be able to do this.
> > > 
> > > 
> > > _____________________________________________________
> > > karim ismail
> > > Network Security
> > > AT&T Global Network Services      internet: karimi@ca.ibm.com
> > > 
> > > 
> > > sirving@ca.ibm.com on 10/05/99 01:31:37 PM
> > > 
> > > Please respond to sirving@ca.ibm.com
> > > 
> > > To:   "Eli Tovbeyn" <eli@xpert.com>
> > > cc:   fw-1-mailinglist@lists.us.checkpoint.com
> > > Subject:  RE: [FW1] Netmasks on different NIC's
> > > 
> > > 
> > > 
> > > 
> > > 
> > > The problem is with supernets.  I don't believe that all systems will support
> > > supernets so you can have problems with 192.168.0.0/16 networks.
> > > 
> > > 
> > > "Eli Tovbeyn" <eli@xpert.com> on 10/05/99 11:40:51 AM
> > > 
> > > Please respond to "Eli Tovbeyn" <eli@xpert.com>
> > > 
> > > To:   fw-1-mailinglist@lists.us.checkpoint.com
> > > cc:
> > > Subject:  RE: [FW1] Netmasks on different NIC's
> > > 
> > > 
> > > 
> > > 
> > > 
> > > Hi,
> > > AFAIK, classfull routing is dead. It was dead even 2 years ago... Every
> > > routing protocol can handle netmasks (well RIP 1.0 can't ). There is no
> > > problem to work with 192.168.0.0/24 or 10.0.1.0/24.
> > > 
> > > -----------------------------------------------------------------
> > > Eli Tovbeyn                           eli@xpert.com
> > >  Senior Consultant               +972-9-9522378
> > >   Xpert Trusted Systems   +972-5-3574884
> > > 
> > > 
> > > 
> > > 
> > > > -----Original Message-----
> > > > From: owner-fw-1-mailinglist@lists.us.checkpoint.com
> > > > [mailto:owner-fw-1-mailinglist@lists.us.checkpoint.com]On Behalf
> > > > Of Carric Dooley
> > > > Sent: Monday, October 04, 1999 7:24 PM
> > > > To: Earl Robinson
> > > > Cc: fw-1-mailinglist@lists.us.checkpoint.com
> > > > Subject: Re: [FW1] Netmasks on different NIC's
> > > >
> > > >
> > > >
> > > > I think it has someting to do with the fact that 192.168.x.x is NOT a
> > > > class B network.  It is in the Class C range.  If you are going
> > > > to bring class
> > > > into it, us a class B. I have seen routers do bizarre things when you go
> > > > against the natural mask.  The only protocol that supports supernetting
> > > > (for route aggregation) is BGP.
> > > >
> > > > On Mon, 4 Oct 1999, Earl Robinson wrote:
> > > >
> > > > >
> > > > > This looks exactly right to me. I'm not clear on why Carrick
> > > > Dooley says you cant
> > > > > use 192.168.xxx.xxx as a class B network. But anyway....
> > > > >
> > > > > What is your vendor's explanation of why this won't work?? Not
> > > > enough $$$ in it for
> > > > > them or what?
> > > > > -earl
> > > > >
> > > > > "Van Schijndel, Art - TOH" wrote:
> > > > >
> > > > > > Bjornar,
> > > > > >
> > > > > > I do variable length subnetting on my firewalls with no problem.  Your
> > > > > > subnet boundaries look a little funny to me, however.  Bounce
> > > > this off your
> > > > > > vendor:
> > > > > >
> > > > > > > NIC1: xxx.xxx.xxx.33-64 mask 255.255.255.224 (32 addresses)
> > > > > > NIC1: xxx.xxx.xxx.32-63 mask 255.255.255.224 (30 usable addresses)
> > > > > >
> > > > > > > NIC2: xxx.xxx.xxx.65-96 mask 255.255.255.224 (32 addresses)
> > > > > > NIC2: xxx.xxx.xxx.64-95 mask 255.255.255.224 (30 usable addresses)
> > > > > >
> > > > > > > NIC3: xxx.xxx.xxx.97-104 mask 255.255.255.248 (8 addresses)
> > > > > > NIC3: xxx.xxx.xxx.128-135 mask 255.255.255.248 (6 usable addresses)
> > > > > >
> > > > > > > NIC4: xxx.xxx.xxx.105-112 mask 255.255.255.248 (8 addresses)
> > > > > > NIC4: xxx.xxx.xxx.136-143 mask 255.255.255.248 (6 usable addresses)
> > > > > >
> > > > > > > NIC5: xxx.xxx.xxx.113-144 mask 255.255.255.224 (32 addresses)
> > > > > > NIC5: xxx.xxx.xxx.96-127 mask 255.255.255.224 (30 usable addresses)
> > > > > >
> > > > > > Best regards,
> > > > > >
> > > > > > Art
> > > > >
> > > > >
> > > > >
> > > > >
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