From: P729 (p729@cox.net)
Date: Sat Aug 30 2003 - 22:28:26 GMT-3
The VLAN bounds your broadcast domain, so the question is, how far do you
want your broadcasts to go? If every host shares the same subnet mask they
will simply ARP for any other host in the 172.30.16.0/21 address space. If
you don't span your VLAN across all of the sites via trunking you will only
be able to reach local hosts. If you carve up the 172.30.16.0/21 address
space into smaller subnets and assign those subnets to independent VLANs at
each site, you must then route between them. Although _collectively_ they
will share the 172.30.16.0/21 address space, the hosts must check the
destination address against their own IP address and subnet mask to see if
they need to go look for a gateway to go off-net to a part of the
172.30.16.0/21 address space that isn't local. Obviously, you must allocate
your addresses among the sites carefully, otherwise your interface
definitions and routing tables will look horrible.
Regards,
Mas Kato
https://ecardfile.com/id/mkato
----- Original Message -----
From: "emad" <emad@zakq8.com>
To: "'Larry Letterman'" <lletterm@cisco.com>; "'Gary Bartlett'"
<gary.bartlett@consultant.com>; <ccielab@groupstudy.com>
Sent: Thursday, August 28, 2003 12:37 AM
Subject: RE: Vlan design vs. subnet distribution
> The case exactly is I have three or more sites connected through edge
> switch to the core switch (4507) through fiber links but all these sites
> share the subnet 172.30.16.0 mask 255.255.248.0 , how can I implement
> vlans between these sites with the existing subnet range right there.
>
> Please advice
>
>
> -----Original Message-----
> From: emad [mailto:emad@zakq8.com]
> Sent: Thursday, August 28, 2003 10:22 AM
> To: 'Larry Letterman'; 'Gary Bartlett'; 'ccielab@groupstudy.com'
> Subject: RE: Vlan design vs. subnet distribution
> Importance: High
>
> Larry , u didn't get my point at all
> All these sites are connected by fiber to the core switch , all the
> network around are flat network (one broadcast domain) no L3 routers in
> between , u got it now?
>
> -----Original Message-----
> From: Larry Letterman [mailto:lletterm@cisco.com]
> Sent: Thursday, August 28, 2003 10:19 AM
> To: 'Gary Bartlett'; 'emad'; ccielab@groupstudy.com
> Subject: RE: Vlan design vs. subnet distribution
>
> I raelly don't see what vlans have to do with connecting remote
> Sites, since most remotes are connected by routers with L3 subnets
> Using /30 space. The most common way of connecting remotes to the main
> Site on one subnet would be multipoint frame...
>
>
> Larry Letterman
> Cisco Systems
>
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Gary Bartlett
> Sent: Thursday, August 28, 2003 12:14 AM
> To: emad; ccielab@groupstudy.com
> Subject: Re: Vlan design vs. subnet distribution
>
>
> Well, I think you were on the right track by saying that for routing
> purpoces it wouldn't work to well if you had multiple sites advertiseing
> the same subnet, unless the subnets were NATed by the router as it was
> advertised to the rest of the network...
>
>
> ----- Original Message -----
> From: "emad" <emad@zakq8.com>
> Date: Thu, 28 Aug 2003 09:59:31 +0300
> To: <ccielab@groupstudy.com>
> Subject: Vlan design vs. subnet distribution
>
> > Folks,
> > I faced a question saying why it is necessary to dedicate one subnet
> > per each vlan and not more when we are connecting , as example , two
> > branch sites switches to the core switch? My answer was to how we can
> > give IP to each vlan interface on the core switch to make L3 routing
> > between them and at the same time we limited the boradcast traffic to
> > inside the same site, but if I have three sites(one head quarter and
> > other two are branches) have one subnet in between them ?
> > Like if I have subnet 172.30.16.0 255.255.248.0 distributed between
> the
> > three sites , how can I make vlans without having each site separated
> > into one subnet!!!
> >
> > Please advice
> >
> > thanx
> >
> >
> > ______________________________________________________________________
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