[c-nsp] Vlan interface vs. sub-interface

[Phil Mayers]

Nate wrote:
> I'm trying to put together a table of advantages (and disadvantages)
> of a vlan interface (SVI) vs. a sub-interface of a physical port. So
> far, I have the following.

Assuming you are talking about layer3 routed interfaces, then basically;

  * On platforms that support SVIs, you should generally use SVIs. On 
those platforms, sub-ints are generally implemented using "hidden" SVIs 
magically picking a vlan tag (that you might later need) so there's no 
"number of interfaces" difference, and disabling spanning tree is pretty 
trivial

  * On platforms that only support sub-ints, obviously you use sub-ints

> 
> SVI
> ----
> Advantage:
> -Ability to add redundant link to the L3 interface
> -Better counter and statistics displayed through CLI
> 
> Disadvantage:
> -Need to be mindful of Spanning Tree issues on redundant links
> -The number of SVI supported maybe limited dependent on platform?
> 
> 
> 
> Physical port sub-interface
> ---------------------------------
> Advantage:
> -Easier to configure and supported on more platforms?
> 
> 
> Disadvantage:
> -Inability to add L2 redundant links
> -Statistics on CLI limited
> -Bandwidth limited to physical port
> 
> 
> Are there more significant advantages/disadvantages (e.g. buffer
> limit, queue depth) that I'm missing?
> 
> Thanks,
> Nate
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