[c-nsp] general question on VRFs and FIBs...

[Keegan Holley]

2011/9/27 Robert Raszuk <robert at raszuk.net>

> Hi Keegan,
>
>
>  over another.  However, if the vrf's all have separate tables in the real
>> world then that should require the table lookup to come before the prefix
>> lookup.  If not there would be no way to figure out which fib to search.
>>
>
> For packets coming from customer (CE) there is no need for any additional
> lookup as switching vectors of the interfaces (logical/physical) are already
> locked to a given VRF.
>
> /* One exception of the above is Policy Based VRF selection where you are
> choosing VRF dynamically based on preconfigured policy or even remote radius
> lookup. in this configuration interfaces are not bounded to any VRF. */
>
> For packets coming from the core to a PE the VPN label directly points to
> the right VRF (per vrf label/aggregate label case). For per CE or per prefix
> labels no IP lookup is necessary in the VRFs at all for packets going to the
> CE.
>


I think you misunderstood.  This is all part of the same lookup.  The first
is matched by the interface, the second by policy and the third by mpls
tag.  My point is that it is the same operation across multiple FIBs or a
single FIB.