[cisco-voip] phones working on a dumb switch with voice/data vlans switched properly

[Nick Barnett]

It’d be interesting to see what a wireshark trace looks like. I think Dave
is spot on. If you span the PC port on the phone then run a capture, you
SHOULD probably be able to see the VLAN tag for those phone packets. I
would expect the packets destined for the laptop behind the phone to be
untagged. You could probably see both in a single trace. Everything seems
to be working, it's just fun to dig in sometimes.

On Wed, Oct 3, 2018 at 7:59 PM Lelio Fulgenzi <lelio at uoguelph.ca> wrote:

>
> Well, I certainly learned something today. Thx for the feedback.
>
> *-sent from mobile device-*
>
>
> *Lelio Fulgenzi, B.A.* | Senior Analyst
>
> Computing and Communications Services | University of Guelph
>
> Room 037 Animal Science & Nutrition Bldg | 50 Stone Rd E | Guelph, ON |
> N1G 2W1
>
> 519-824-4120 Ext. 56354 <519-824-4120;56354> | lelio at uoguelph.ca
>
>
>
> www.uoguelph.ca/ccs | @UofGCCS on Instagram, Twitter and Facebook
>
>
>
> [image: University of Guelph Cornerstone with Improve Life tagline]
>
> On Oct 3, 2018, at 8:23 PM, Dave Goodwin <dave.goodwin at december.net>
> wrote:
>
> Not necessarily. Unmanaged switches that do not support 802.1q will often
> just forward frames as is, tags and all, and only operate on the other
> parts of the L2 header they pay attention to (source/destination address).
> I have also seen unmanaged switches that did not claim support for 802.1q
> and ATE my tags.
>
> On Wed, Oct 3, 2018 at 6:16 PM Lelio Fulgenzi <lelio at uoguelph.ca> wrote:
>
>>
>> Ok. I hear ya. But wouldn’t the switch need to support 802.1q to support
>> those tagged packets?
>>
>> This switch didn’t specify that it supported 802.1q.
>>
>>
>>
>> *-sent from mobile device-*
>>
>>
>> *Lelio Fulgenzi, B.A.* | Senior Analyst
>>
>> Computing and Communications Services | University of Guelph
>>
>> Room 037 Animal Science & Nutrition Bldg | 50 Stone Rd E | Guelph, ON |
>> N1G 2W1
>>
>> 519-824-4120 Ext. 56354 <519-824-4120;56354> | lelio at uoguelph.ca
>>
>>
>>
>> www.uoguelph.ca/ccs | @UofGCCS on Instagram, Twitter and Facebook
>>
>>
>>
>> [image: University of Guelph Cornerstone with Improve Life tagline]
>>
>> On Oct 3, 2018, at 5:47 PM, Dave Goodwin <dave.goodwin at december.net>
>> wrote:
>>
>> I haven't really tried the kind of thing you described in quite a long
>> time. But I assume the reason the phone gets an IP address is because the
>> CDP VVLAN information is being successfully sent through the unmanaged
>> non-Cisco switch so the phone actually sees it. The phone learns its VVLAN
>> ID, so starts tagging all its frames and therefore gets an IP from the
>> VVLAN. The other devices plugged into the switch (or behind the phone)
>> don't normally need to tag, so the frames are coming through up to the
>> Cisco switch untagged and are therefore in the native/access VLAN on the
>> port and getting one of those IPs.
>>
>> So I guess that unmanaged switch passes any CDP through to all ports, and
>> also passes any tagged traffic through unaltered.
>>
>> On Wed, Oct 3, 2018 at 5:17 PM Lelio Fulgenzi <lelio at uoguelph.ca> wrote:
>>
>>>
>>> OK - I'm probably showing my ignorance here, but I was quite surprised
>>> to find out that plugging in a dumb Dlink DES-105 switch into our cisco
>>> switch with access layer programming, so data vlan and voice vlan, extended
>>> things such that when a phone is plugged in, it got an IP address on the
>>> voice vlan, and plugging a non-phone device got an ip address on the data
>>> vlan and then plugging a similar device into the back of the phone also got
>>> an ip address on the data vlan. We plugged in multiple phones as well. All
>>> worked fine. *phones powered by brick*
>>>
>>> I can appreciate a passthrough device, I've used them before as ethernet
>>> extenders. By what I'm not understanding is how traffic is being classed
>>> properly through to this dumb switch.
>>>
>>> We're using a new 9300 series switch, but I'm not sure that would make a
>>> difference.
>>>
>>>
>>>
>>> ---
>>> Lelio Fulgenzi, B.A. | Senior Analyst
>>> Computing and Communications Services | University of Guelph
>>> Room 037 Animal Science & Nutrition Bldg | 50 Stone Rd E | Guelph, ON |
>>> N1G 2W1
>>> 519-824-4120 Ext. 56354 | lelio at uoguelph.ca<mailto:lelio at uoguelph.ca>
>>>
>>> www.uoguelph.ca/ccs<http://www.uoguelph.ca/ccs> | @UofGCCS on
>>> Instagram, Twitter and Facebook
>>>
>>> [University of Guelph Cornerstone with Improve Life tagline]
>>>
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