[Xorp-hackers] Doubt on VLAN implementation

Bruce M Simpson bms at incunabulum.net
Mon Mar 24 13:30:52 PDT 2008

Pavlin Radoslavov wrote:
> I have to admit that when comes to VLANs I am thinking the IEEE
> 802.1Q Standard.
> How the relationships you describe above fit with 802.1Q?
> If you have an URL with detailed description that would be useful.

There are folk out there using multiple 802.1Q encapsulation headers, 
particularly for stuff like Metro Ethernet. It is sometimes called "Q-in-Q".

The encapsulation thing was a requirement crunch when rethinking the 
FreeBSD ether_input() path this time last year -- and all I wanted to do 
was make 802.1p work with my VoIP ATA...

I didn't see any reason to support more than 2 levels of encapsulation 
on the same link layer, however it's entirely possible people are doing 
more than 2.

Having said that, I'd like to see how Q-in-Q is configured on vendor 
equipment before making any radical changes anywhere. For XORP, 
personally I prefer the interface foo0 { vif vlan10 { ... }  } style 
syntax, but how to capture Q-in-Q in that syntax is an open question.


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