Re: Bridging VLANs by looping cable

From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Tue Jul 31 2007 - 07:49:52 ART


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
>>>
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-- 
Carlos G Mendioroz  <tron@huapi.ba.ar>  LW7 EQI  Argentina


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