Re: MPLS Route Targets

Sorry, I don't get a clear message from you, although I think I do
understand what the command does :-/

Confusion items:
* You put in the bag RDs and RTs, and AFAIK, this is only RT related.
* You talk about being required to send... and that make no sense to me.
* You even talk about LDP and second label, when AFAIK this is a control
plane thing, BGP only.

What my understanding is now is that this is an implicit filter based on
import targets to reduce the BGP table size of PEs.
And a nasty surprise if your PE talks eBGP to someone that wants that
information, or if the router is a reflector, or confed intra AS boundary.
Or said another way, this filter is designed for leaf PEs that only care
about prefixes for their VRFs, and you'd better disable it if the router
is in a BGP transit path.

-Carlos

Paul Negron @ 22/08/2010 3:16 -0300 dixit:
> Man I almost confused myself. Here is the answer simplified.
>
> By default, a router that DOES NOT have the RT and RD information will
> reject the routes as not supporting the extended-community value and will
> NOT be visible in the bRIB.
>
> The route-target filter allows a VPNv4 participating router to view both the
> route-target and the RD information even when it does not have the RT or RD
> information defined.
>
> The newly learned RT and RD information can then be shared with ANOTHER
> VPNv4 (E)BGP peer. When the route-target filter is removed from the new EBGP
> peer, the bRIB learns the RD and RT information from the Originating EBGP
> peer.
>
> This proves that the route-target filter command is not required to send BGP
> information. It is ONLY used to reveal information that was at one time
> rejected. This also allows the BGP peer to advertise these routes to another
> peer.
>
>
> Sorry folks. A little late for me to be answering questions.
> Hope this helps.
>
> Paul
>
> Paul Negron
> CCIE# 14856 CCSI# 22752
> Senior Technical Instructor
> www.micronicstraining.com
>
>
>
>> From: Paul Negron <negron.paul_at_gmail.com>
>> Date: Sat, 21 Aug 2010 23:15:23 -0600
>> To: Carlos G Mendioroz <tron_at_huapi.ba.ar>
>> Cc: Adam Booth <adam.booth_at_gmail.com>, Brad Edgeworth <edgie512_at_gmail.com>,
>> Cisco certification <ccielab_at_groupstudy.com>
>> Conversation: MPLS Route Targets
>> Subject: Re: MPLS Route Targets
>>
>> Ah! I think the confusion here is the purpose of the command. The purpose is
>> to prevent a PE router from making those route-targets visible to ANY
>> upstream BGP peer that does not configure the RT that matched the Downstream
>> PE.
>>
>> That said, If the 2 EBGP P routers can remove the route-target filter and use
>> the inner most label to send traffic, then the command is NOT REQUIRED to pass
>> on RD and RT information with the (NON-LDP) VPNv4 EBGP peer. Try and say that
>> 10 times. Crap!! :-)
>>
>> Does this make sense?
>>
>>
>> --
>> Paul Negron
>> CCIE# 14856 CCSI# 22752
>> Senior Technical Instructor
>> www.micronicstraining.com
>>
>>
>>
>>> From: Carlos G Mendioroz <tron_at_huapi.ba.ar>
>>> Date: Sat, 21 Aug 2010 08:02:43 -0300
>>> To: Paul Negron <negron.paul_at_gmail.com>
>>> Cc: Adam Booth <adam.booth_at_gmail.com>, Brad Edgeworth <edgie512_at_gmail.com>,
>>> Cisco certification <ccielab_at_groupstudy.com>
>>> Subject: Re: MPLS Route Targets
>>>
>>> Cool.
>>> Just one question, as I have never labbed nor have experience in
>>> inter-AS mpls vpns: You say "in order to see" the route targets,
>>> but my impression of the command (no bgp default route-target filter)
>>> is that it actually filters, so for a reflector or a vpnv4 eBGP peer,
>>> you would actually need it in order to exchange such routes
>>> (those with no RTs used by local VRFs). Is that correct ?
>>>
>>> Thanks,
>>> -Carlos
>>>
>>> Paul Negron @ 20/08/2010 21:52 -0300 dixit:
>>>> All,
>>>>
>>>> When configuring Inter-AS VPN, The P routers ARE participating in BGP under
>>>> the VPNv4 Address-Family and will use the inner label to switch from carrier
>>>> to carrier. The default route target must be lifted in order to see the
>>>> route-targets on the P router. The only other way I know of is to configure
>>>> the route-targets on a vrf that is on the P router but not applied to any
>>>> interfaces.
>>>>
>>>> A similar problem would take place when using Confederations.
>>>>
>>>> The command that dumps the information on that P router or ANY router that
>>>> the route-targets are not configured on, is " no bgp default route-target
>>>> filter" under the BGP process. All of the RD information is seen. Even more
>>>> than a router that has the RT's configured.
>>>>
>>>>
>>>> Paul
>>> --
>>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>
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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net