Let's look at what each one does:
Router: Routes protocols (IP, IPX, AppleTalk, etc.). If it doesn't know the
procotol, it can't route it.
Bridge: Works at layer 2 and only deals with MAC addresses and could care
less about the protocol at layer 3.
Brouter: Routes protocols it knows, bridges protocols it doesn't know/that
are unroutable (no layer 3 addressing).
Layer 3 switch example:
VLAN1: Ports 1-2 10.0.1.0/24
VLAN2: Ports 3-4 10.0.2.0/24
VLAN1 + 2: Ports 5-6 10.0.1.0/24 + 10.0.2.0/24
It can route packets between the VLANs.
It can switch/bridge at layer 2 between ports in the same VLAN.
For multi-VLAN ports it can switch/bridge between ports and also do
essentially "local" routing between ports, but you losing the advantages of
having a VLAN (security, separate broadcast domains, etc.) when you have
multi-VLAN ports. You also lose control of what you want don't want
bridged/switched (stuff you're not routing, but also have no way to block at
layer 2 if you bridge/switch).
I'm also not clear on what switches can handle multi-VLANs for the same port
(not trunking, mind you). I don't believe most can.
Anyway, just some thoughts on the whole thing.
Jason Roysdon, CCNA, MCSE, CNA, Network+, A+
List email: [EMAIL PROTECTED]
Homepage: http://jason.artoo.net/
Cisco resources: http://r2cisco.artoo.net/
"Priscilla Oppenheimer" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> I was taking the old-fashioned view that Layer-3 switch = router. I
hadn't
> considered what Jay said that it's a "Layer-3 and below" device and it
> could be doing Layer-2 switching (bridging) for devices all in the same
> VLAN and the same subnet, as you say.
>
> Sounds like a Layer-3 switch by this new definition is nothing more than a
> brouter! Nothing every really changes. We've been having this same
> discussion for 15 years. %-}
>
> Priscilla
>
> At 08:14 PM 10/6/00, Chris Larson wrote:
> >I think you may be mistaken.
> >
> > If all ports are in a single Vlan then it is one broadcast domain and
32
> >collision domains.
> >If you split it into 2 Vlans then you have 2 broadcast domains and 32
> >collision domains.
> >
> >If a 32 port switch had 32 broadcast domains then no broadcasts would
ever
> >be forward to other ports even if all the devices plugged into it were in
> >the same vlan and subnet.
> >
> >
> >----- Original Message -----
> >From: "Priscilla Oppenheimer" <[EMAIL PROTECTED]>
> >To: "NetEng" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
> >Sent: Wednesday, October 04, 2000 3:06 PM
> >Subject: Re: Layer3 switching--Follow Up Question
> >
> >
> > > At 09:17 AM 10/4/00, NetEng wrote:
> > > >Does a 32 port layer3 switch module then have 32 collision/broadcast
> >domains?
> > >
> > > Yes.
> > >
> > > > What about broadcast based services?
> > >
> > > What about it??
> > >
> > > Priscilla
> > >
> > > >
> > > >
> > > >>""NetEng"" <<mailto:[EMAIL PROTECTED]>[EMAIL PROTECTED]> wrote
in
> > > >>message
> ><8rdafq$kqb$[EMAIL PROTECTED]">news:8rdafq$kqb$[EMAIL PROTECTED]>8rdafq$kqb$[EMAIL PROTECTED]">news:8rdafq$kqb$[EMAIL PROTECTED]...
> > > >>What are the benefits of layer3 switching (versus layer2)? Can I
create
> > > >>VLAN's w/o using a router on a layer3 switch?
> > >
> > >
> > > ________________________
> > >
> > > Priscilla Oppenheimer
> > > http://www.priscilla.com
> > >
> > > **NOTE: New CCNA/CCDA List has been formed. For more information go to
> > > http://www.groupstudy.com/list/Associates.html
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> > > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html
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> > >
>
>
> ________________________
>
> Priscilla Oppenheimer
> http://www.priscilla.com
>
> **NOTE: New CCNA/CCDA List has been formed. For more information go to
> http://www.groupstudy.com/list/Associates.html
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