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I'm new to VLANs, so take that into consideration...

Lets say that I had a server set up to create a virtual interface that is set to be tagged as VLAN 3. For example, the following Debian config:

iface eth0.3 inet static
    address 192.168.1.1
    netmask 255.255.255.0

Now on my switch, lets say that I have the port that the aforementioned server connects to, set to VLAN 4...

Who wins? What are the packets tagged as, as viewed by the rest of the network?

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Most likely no traffic will pass in either direction. The machine is only looking for packets tagged VLAN 1. And depending on how you configured the switch, it's either only looking for untagged packets, only looking for packets tagged with VLAN 4, or looking for either of those but definitely not looking for packets tagged with VLAN 1. –  David Schwartz Oct 15 '12 at 23:07
    
I see, thank you. Please post that as an answer... –  Soviero Oct 15 '12 at 23:15
    
Is the switch set to tagged (filtering for VLAN 4) or untagged (and maps everything untagged into VLAN 4) for that port? Some switches can filter VLANs (for bandwidth management, security, etc). –  Skaperen Oct 16 '12 at 0:05

1 Answer 1

up vote 2 down vote accepted

Most likely no traffic will pass in either direction. The machine is only looking for packets tagged VLAN 3. And depending on how you configured the switch, it's either only looking for untagged packets, only looking for packets tagged with VLAN 4, or looking for either of those but definitely not looking for packets tagged with VLAN 3.

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Would you mind editing the answer to match the edited question? (Change VLAN 1 to VLAN 3) –  Soviero Oct 15 '12 at 23:44
    
The reference to VLAN 1 is saying that VLAN 1 is definitely not configured. The problem in the original question is that the Debian system is configured to work with tagged packets and only with tag for VLAN 3. The switch may be looking for tagged and filtered to VLAN 4, or not tagged and passing everything not tagged into VLAN 4. The conflict is simply a mutually exclusive case. –  Skaperen Oct 16 '12 at 0:03
    
For some odd reason, the VLAN in the question was changed from 1 to 3. It doesn't really affect the answer, except it makes it more certain as some machines might accept untagged packets as if they were tagged for VLAN 1, but certainly not for 3. –  David Schwartz Oct 16 '12 at 10:24

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