The MPLS-OPS Archive

["alok" <alok.dube@apara.com>]

Hi Rajiv,

RTs are defined in the same RC2547,

i was generally wondering as to why they are ever used... i mean we cud use
communities itslef...why write a whole new attribute?

I guess one way of seeing it is "when i want to distribute routes across
VPNs" ..

would appreciate any help here...if someone could clarify this...

-rgds
Alok




----- Original Message -----
From: Rajiv Asati <rajiva@cisco.com>
To: alok <alok.dube@apara.com>
Cc: Joseph Anthony <tonyjoe20002002@yahoo.co.in>; <rogerw@nordlink.com>;
<mpls-ops@mplsrc.com>
Sent: Monday, October 14, 2002 2:56 AM
Subject: Re: [MPLS-OPS]: REG: Filtering of MPLS VPN routes


Alok,

At 04:00 PM 10/13/2002, alok wrote:
>well yes....
>
>for starters can u please tell me what ORF means?

Outbound Route filtering, a feature that allows a BGP speaker to advertise
to its BGP neighbors the outbound route filters neighbors should use. These
filters are described in ORF entries, which are part of route-refresh
message.
Yes, it is actually a BGP capability that should be exchanged before the
session comes UP.

In a nutshell, ORF is a way to tell the neighbors that "hey, don't send me
an update/prefix etc, since I don't need it".
This helps to reduce unwanted routing updates.

ORF for prefixes have been existing for quite-a-while as explained below:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1612/products_feature_guid
e09186a008008088c.html

>  and how does cisco carry out BGP updates for multiple VPNs? dont u use
> route distinguishers? as
>proposed in RFC2547 ?

Of course.
[ So VPNv4 address is RD:IPv4.And the MP-BGP update contains this VPNv4
address along with an extended-community RT.]


Now in MPLS VPN context, ORF support gets extended to extcomm. (I don't
know about the IETF draf for this one).

I guess your Q is really: why RT, why not RD for ORF ?
Having RD based ORF may defeat the purpose of extranet, since a PE might
not have a certain VRF configured, but still accepting routes (from that
VPN) into another VPN based on RT.

Hope this helps.
Cheers,
Rajiv




>----- Original Message -----
>From: Rajiv Asati <rajiva@cisco.com>
>To: alok <alok.dube@apara.com>
>Cc: Joseph Anthony <tonyjoe20002002@yahoo.co.in>; <rogerw@nordlink.com>;
><mpls-ops@mplsrc.com>
>Sent: Monday, October 14, 2002 1:14 AM
>Subject: Re: [MPLS-OPS]: REG: Filtering of MPLS VPN routes
>
>
>Alok,
>
>At 10:29 AM 10/13/2002, alok wrote:
> >have been following this thread for a while so ...as i started getting
> >lost, i thought id ask a question....
> >
> >wouldnt RRs be "per vrf based"?
>
>RR typically does not have any VRF configured.
>Are you referring to any other implementation ?
>
>  From my understanding,  Joseph was referring to extcomm based filtering
on
>RR. Since he mentioned IOS CLI "bgp rr-group", I assumed he was referring
>to Cisco's implementation.
>
>Cheers,
>Rajiv
>
> >so in that case wudnt the vrf be assoicated with a "RD" flag...?
> >
> >how would ever spill over routes at all...i guess u mean "spill over
> >routes of other VPNs".... then the answer is you wont coz the NLRIs have
> >the RD field indicating which VPN the route belongs too....
> >
> >so i doubt if u will ever need filters at all.....
> >for this case...unless u want to block certain routes in the same VPN...
> >
> >unless cisco does something different from "RDs"...havent done MPLS VPNs
> >on cisco but only junipers and zebra etc..so am not sure on this...
> >
> >-rgds
> >Alok
> >>----- Original Message -----
> >>From: <mailto:tonyjoe20002002@yahoo.co.in>Joseph Anthony
> >>To: <mailto:rajiva@cisco.com>Rajiv Asati ;
> >><mailto:rogerw@nordlink.com>rogerw@nordlink.com
> >>Cc: <mailto:mpls-ops@mplsrc.com>mpls-ops@mplsrc.com
> >>Sent: Saturday, October 12, 2002 8:23 PM
> >>Subject: Re: [MPLS-OPS]: REG: Filtering of MPLS VPN routes
> >>
> >>  Hi All,
> >>
> >>Thanks for all the inputs. I do have some questions in regard to
> >>Route-Filtering pertaining to Route Reflectors configurations in an MPLS
> >>VPN environment. Assuming the following scenario -
> >>
> >>Now while using Extended community based filtering by means of the ORF
> >>for route filtering. My question is as follows -
> >>
> >>1. In a partitioned RR setup, should all the RR clients and RR server
> >>have the extended community list and bgp-rr group configured on them, in
> >>order to facilitate both outbound and inbound filtering (dynamic).
> >>
> >>Assuming I have 2 RR's, each servicing a set of VPN's. Now in a
situation
> >>in which an existing PE router suddenly needs to service a VPN, to which
> >>it has not provided routes previously, I understand that we would need
to
> >>have the PE router establish an additional session to the other
> >>Route-reflector, which is currently reflecting routes to its clients for
> >>the particular VPN. This requires filtering to happen at the PE, wherein
> >>the PE should not spill over unwanted VPN routes to either of the RR's.
> >>Now while using Extended community based filtering by means of the ORF
> >>for route filtering. My question is as follows -
> >>
> >>1. How would the same work here? Any sample config will be greatly
> >>appreciated.
> >>
> >>Thanks in advance,
> >>
> >>Tony.
> >>
> >>
> >>
> >>Yahoo! Properties Special Buy, sell, rent...your flat, or even post an
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