From: Ben (bmunyao@gmail.com)
Date: Tue Jul 31 2007 - 13:08:25 ART
Hi Ivan,
You are right, when talking about a router. I assumed we were dealing with
PC hosts. Microsoft and Unix hosts tend to add a default route (check with
"route print") in their local routing tables the minute you configure them
with an IP address. Hence the arp resolution attempt for all destinations.
Ben
On 7/31/07, Ivan <ivan@iip.net> wrote:
>
> Hello Ben !
>
> Host send ARP broadcast only if host is directly connected. If there is
> no
> network in RIB, host will not send ARP. You must revise your concept.
>
> On Tuesday 31 July 2007 17:23, Ben wrote:
> > Just when i thought I had it figured. What happens at ARP level?
> >
> > Just to break it down.
> >
> > 1. Host in vlan1 sends ARP broadcast.
> > 2. broadcast flooded to all vlan1 ports, including port with cable
> > interconnecting vlan1 to vlan2.
> > 3. afaik, vlan2 port should drop the broadcast. Now I'm not sure what
> > happens at this stage.
> >
> > assuming we put aside our routing knowledge for a moment:
> >
> > 4.If broadcast flooded through vlan2, destination host receives it and
> > unicasts its IP back.
> > 5. Unknown unicast flooded to all vlan2 ports including interconnection
> > port.
> > 6 host in vlan1 caches entry and sends unicast data. Or does it? When it
> > detects the source as being from another IP subnet, shouldn't it drop
> the
> > arp response packet? If from same subnet, it will accept the entry.
> > 7 If same subnet, indeed they should communicate. If not, I'm not sure
> what
> > happens next.
> >
> > Perhaps someone else can demystify this communication further.
> >
> > Ben
> >
> > On 7/31/07, Carlos G Mendioroz <tron@huapi.ba.ar> wrote:
> > > Hmm, you are for a surprise if you think so.
> > > Yes, this works, and there are some setups where this may prove
> useful.
> > >
> > > Like some switches that only support one private vlan promiscuous port
> > > and you need to connect a couple.
> > > Or some restrictions on where you can rate limit on some
> architectures.
> > > (E.g. you can go to a real L3 interface from a L2 access)
> > >
> > > Nothing really clean, and I would not recomend doing that anywhere,
> but
> > > works... like most hacks.
> > >
> > > -Carlos
> > >
> > > Ben @ 31/07/2007 07:13 -0300 dixit:
> > > > Martijn,
> > > >
> > > > VLANs by design confine traffic to the vlan, unless it has been
> routed
> > > > across to another vlan. Merely connecting a cable between two VLANs
> > > > therefore does not circumvent this behavior, even if hosts in the
> two
> > >
> > > vlans
> > >
> > > > use the same IP subnet.
> > > >
> > > > Ben
> > > >
> > > > On 7/31/07, martijn <groupstudy@martijnj.nl> wrote:
> > > >> Lim,
> > > >>
> > > >> i needed to laugh a little at first. Never tried.
> > > >>
> > > >> Not THE answer, I think you need to test.
> > > >>
> > > >> let's break up your q's.
> > > >>
> > > >>> done before?
> > > >>
> > > >> No.
> > > >>
> > > >>> Can a host on VLAN359 now communicate with a host on VLAN360?
> > > >>
> > > >> After i read your post trice, i see you want to do it @ one switch.
> > >
> > > when i
> > >
> > > >> want to do comms with an host it starts with ip, if that is not
> local
> > > >> (logical AND) I go for the default gateway. Do your pc's have
> > > >> one?????????????
> > > >>
> > > >> When I look to your Q form another angle, say mac-addr table,
> (never
> > > >> tested,
> > > >> group?) I would say mac-addr binding goes to direct connected prot
> > >
> > > first,
> > >
> > > >> after that I assume that the link would for a L2 link between
> vlan's.
> > >
> > > Any
> > >
> > > >> takes?
> > > >>
> > > >> martijn
> > > >>
> > > >> ----- Original Message -----
> > > >> From: "Toh Soon, Lim" <tohsoon28@gmail.com>
> > > >> To: <ccielab@groupstudy.com>
> > > >> Sent: Tuesday, July 31, 2007 9:43 AM
> > > >> Subject: Bridging VLANs by looping cable
> > > >>
> > > >>> Hi All,
> > > >>>
> > > >>> This may sound simple and mundane but for curiosity sake, I need
> to
> > >
> > > seek
> > >
> > > >>> clarification.
> > > >>>
> > > >>> Has anyone tried "bridging" two VLANs by looping a cable to the
> same
> > > >>> switch?
> > > >>> E.g. in the following diagram:
> > > >>>
> > > >>> Gi0/1(VLAN359)----
> > > >>>
> > > >>>
> > > >>> Gi0/2(VLAN360)----
> > > >>>
> > > >>> The same cable connects to interfaces Gi0/1 (VLAN359) and Gi0/2
> > > >>
> > > >> (VLAN360).
> > > >>
> > > >>> Can a host on VLAN359 now communicate with a host on VLAN360?
> > > >>>
> > > >>> What's the implication doing this, e.g. from STP point of view? Is
> it
> > > >>> recommended at all?
> > > >>>
> > > >>> Any advice is appreciated.
> > > >>>
> > > >>>
> > > >>> Thank you.
> > > >>>
> > > >>> B.Rgds,
> > > >>> Lim TS
> > >
> > >
> _______________________________________________________________________
> > >
> > > >>> Subscription information may be found at:
> > > >>> http://www.groupstudy.com/list/CCIELab.html
> > > >>
> > > >>
> ______________________________________________________________________
> > > >>_ Subscription information may be found at:
> > > >> http://www.groupstudy.com/list/CCIELab.html
> > > >
> > > >
> _______________________________________________________________________
> > > > Subscription information may be found at:
> > > > http://www.groupstudy.com/list/CCIELab.html
> > >
> > > --
> > > Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
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