[j-nsp] under the hood of MP-BGP

[adamv0025 at netconsultings.com]

Hi folks,

 

Does anyone know any details about what's going on under the hood of MP-BGP
when a new VRF is configured? 

 

I'm only clear about this part: 

When a new RT import is configured or when the RT import is removed, a route
refresh is sent from the PE to RRs for the affected address families
VPNv4/6. 

When a new VRF is configured, the PE sends a route-refresh to RRs. 

In both cases the RRs do send all VPNv4/6 prefixes to the PE. 

(In case of RT filter RRs will only send the set of routes according to the
RT filter advertised by PE). 

 

But what happens next or in parallel? 

Does BGP parse through the local MP-BGP table first in attempt to import at
least the local routes into the NEW VRF as soon as possible? 

With regards to VPN routes coming in from RR, 

does PE wait till EOR/keepalive from RR in order to start best path
selection and then parsing to determine which routes needs to be installed
into the NEW VRF? 

(does BGP read-only mode apply to route-refresh event as well?). 

Or does it actually perform best path selection and then parsing say every
20K routes in attempt to install at least some of the paths into the NEW VRF
while waiting for all the paths to be received? 

 

Are there any mechanisms in use to speed up parsing through the MP-BGP table
and installation of paths into NEW VRF? 

Are VPN routes grouped based on commonalities in RTs? 

-So when a new route falls into one of these groups it inherits all the VRF
groups associated with the RT group. 

Are VPNs grouped based on common import policies? 

-So when a NEW VRF falls into one of these groups it inherits all the RT
groups associated with the VRF group. 

 

 

These questions are OS agnostic, I'd appreciate any pointers.

 

adam

 

 

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