# VLAN ingress?

## deltamalloc

At the following Gentoo wiki link: https://wiki.gentoo.org/wiki/Handbook:X86/Networking/Modular#VLAN_.28802.1q_support.29

What does ingress and egress mean here? I know what ingress and egress means, but what does this syntax mean?

```

vlan1_name="vlan1"

vlan1_ingress="2:6 3:5"

eth0_vlan1_egress="1:2"

```

Does vlan1_ingress="2:6 3:5" mean that frames arriving on vlan1 can have VLAN ID 2 to 6 or 3 to 5? Or does it mean something completely different?

What about eth0_vlan1_egress? Does this mean that frames leaving vlan1 will be tagged with VLAN ID 1 and 2? Or does it mean something completely different?

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## Princess Nell

They are not VLAN ids, but priority mappings involving the PCP field of the 32-bit VLAN header.

If that makes me sound like an expert, I'm not  :Wink:  I just spent some time researching it because the question was interesting and outside my comfort zone. You'd probably need to dig into IEEE 802.1Q and 802.1P to understand this better.

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## deltamalloc

 *Princess Nell wrote:*   

> They are not VLAN ids, but priority mappings involving the PCP field of the 32-bit VLAN header.
> 
> If that makes me sound like an expert, I'm not  I just spent some time researching it because the question was interesting and outside my comfort zone. You'd probably need to dig into IEEE 802.1Q and 802.1P to understand this better.

 

Thanks for the input. I don't think I need to deal with 802.1P at all.

If this doesn't specify how to tag frames, then how is it specified?

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## Princess Nell

The VLAN id is part of the variable name. Check out the vlan section in netifrc net.example.

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