[j-nsp] load balancing in Route reflector scenario

[Keegan Holley]

2011/8/10 Robert Raszuk <robert at raszuk.net>

> Hi Keegan,
>
>
>  I think the advertise inactive knob turns that off, but I don't know for
>> sure because I've never tried it.  I know it's not supported on cisco
>> routers.  The reason for it is the size of the BGP table.  So if the table
>> is 400k routes and you have 5 different ISP's and you advertise every
>> route
>> that would be 2M routes in the table.  Since BGP doesn't allow multiple
>> version of the same route in the routing table (separate from the BGP
>> table
>> where incoming routes are stored) you would still only use the original
>> 400K
>> the other 1.8M routes would just go unused unless you manipulated them
>> some
>> how.
>>
>
> Advertise inactive is not about what get's advertised - it is about if the
> best path is advertised or not. And if is decided based on the check if the
> BGP path to be advertised is inserted in the RIB/FIB or not.
>

Oh I see.  I have never used that command so thanks.  Most of the above
example was what would happen if BGP advertised everything it learned
instead of just the best path or the path in the routing table btw.

>
> By default Junos and IOS-XR advertise only those best path in BGP which
> actually are installed into forwarding. Advertising inactive knob will
> overwrite it.
>

Wouldn't this lead to traffic being blackholed?  If all the routes for a
given destination are inactive would this still cause BGP to advertise a
route for them?

>
> IOS classic/XE (for historical reasons) advertises all best paths from BGP
> table and to enforce it not to advertise what has not been installed into
> RIB/FIB there is knob called "suppress inactive".
>
> Cheers,
> R.
>
>
>
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