Well... I haven't been there yet but It most likely we're gonna see
some kind of inter-as vpn using bgp to exchange labels... In this
case even if the solution works at first in the stable scenario I
would configure send-label in iBGP. Today I have loaded some final
configurations from my completed workbook labs and played with some
failure scenarios. I lost my e2e LSP twice without bgp labels, the
complete solution for those labs were sending the labels within
IBGP. As Rick said LDP relies on IGP to exchange labels and
depending on the topology you got send-label is not a must, but most
of the times it is. You have to undertand the topology and have
concise label exchange secured against failures thru the network.
Rds
Andre
2009/10/31 Bill CCIE <[email protected]>
Even I use send-label that's not necessary I don't think I'll lose
points doing over-config. What do you guys say?
Bill
2009/10/31 André Luiz Bernardes <[email protected]>:
> Got it
>
> I would change that message to : ALWAYS USE SEND-LABEL on IBGP, DO
NOT LOOSE
> POINTS! :)
>
> Thanks
>
> 2009/10/31 Rick Mur <[email protected]>
>>
>> That message is quite dangerous to assume.
>> Like you saw when the EBGP prefix (where labels are exchanged on
the
>> ASBR's) is NOT known in your IGP topology. LDP only assigns
labels to IGP
>> prefixes. Therefore the labels that are exchanged on the AS
border, are NOT
>> known within that network, like Bryan said, on the RR's.
>> You definitely NEED to add send-label on your IBGP neighbors as
well so
>> the traffic is label switched within your AS as well. It will
definitely
>> won't work if you have a couple routers within your AS (when they
are NOT
>> ASBR's). So it's not always when you have 2 connections, it
depends on the
>> situation, check your LFIB and see how the traffic is label
switched (or
>> not)
>> --
>>
>> Regards,
>>
>> Rick Mur
>> CCIE2 #21946 (R&S / Service Provider)
>> Sr. Support Engineer – IPexpert, Inc.
>> URL: http://www.IPexpert.com
>> On 30 okt 2009, at 20:34, André Luiz Bernardes wrote:
>>
>> Hey Brian and Shai
>>
>> I believe some things are for the better !!! Since this morning I
>> believed that sending labels other than to EBGP was just cosmetic
as all the
>> labs I'd done worked fine without that. What I didn't took in
account was
>> what happened when we have dual IPV4 eBGP between the ASs and for
some
>> reason traffic is asymmetrical or just preferring the IBGP path
to reach the
>> next-hop.
>>
>> I am working on INE workbook right now and could reproduce this
issue.
>> What happened was that the VPN PE router was also the ASBR and
instead of
>> preferring the ASBR interface to get to the next AS, it was doing
so via
>> IBGP than taking the second ASBR.
>>
>> Sorry to post outputs from another vendor workbook but I can wait
to share
>> that :)
>>
>>
>> I am sitting on the PE router on AS 100, which is also de ASBR.
The PE
>> router on AS 200 is 20.1.1.1
>>
>> Rack1R7#ping 119.0.0.1 sou lo0
>> Sending 5, 100-byte ICMP Echos to 119.0.0.1, timeout is 2 seconds:
>> Packet sent with a source address of 10.1.7.7
>> .....
>> Success rate is 0 percent (0/5)
>>
>>
>> Rack1R6#sh ip cef 20.1.1.1 detail
>> 20.1.1.1/32, version 185, epoch 0, cached adjacency 20.1.46.4
>> 0 packets, 0 bytes
>> tag information set, shared
>> local tag: BGP route head
>> via 20.1.4.4, 4 dependencies, recursive
>> next hop 20.1.46.4, Ethernet0/0 via 20.1.4.4/32
>> valid cached adjacency
>> tag rewrite with Et0/0, 20.1.46.4, tags imposed: {} <<<<<
NO
>> LABEL HUMMMMMMMM
>>
>>
>>
>> Rack1R6#sh ip bgp labels
>> Network Next Hop In Label/Out Label
>> 20.1.1.1/32 20.1.4.4 nolabel/nolabel <<<<< No
label from
>> iBGP path
>> 20.1.1.1/32 20.1.26.2 nolabel/20 <<<<<
There is a
>> label here learned via eBGP
>>
>>
>>
>> **** I CONFIGURED SEND-LABEL BETWEEN MY IBGP NEIGHBORS WITHIN
AS 100
>> *****
>>
>>
>> Rack1R6#sh ip cef 20.1.1.1 detail
>> 20.1.1.1/32, version 193, epoch 0, cached adjacency 20.1.46.4
>> 0 packets, 0 bytes
>> tag information set
>> local tag: 29
>> fast tag rewrite with Et0/0, 20.1.46.4, tags imposed: {31}
>> via 20.1.4.4, 4 dependencies, recursive
>> next hop 20.1.46.4, Ethernet0/0 via 20.1.4.4/32
>> valid cached adjacency
>> tag rewrite with Et0/0, 20.1.46.4, tags imposed: {31} <<<<<
HERE IS
>> MY LABEL GUYS!!!!!!!!!!
>>
>>
>> Rack1R6#sh ip bgp labels
>> Network Next Hop In Label/Out Label
>> 20.1.1.1/32 20.1.4.4 29/31 <<<<< Label
from
>> IBGP
>> 20.1.1.1/32 20.1.26.2 29/20 <<<<< Label
from
>> EBGP
>>
>>
>> NOW MY TRAFFIC GETS THRU!!!!!!!!!!!!!!!!!!!!
>>
>> Rack1R7#ping 119.0.0.1 sou lo0
>>
>> Type escape sequence to abort.
>> Sending 5, 100-byte ICMP Echos to 119.0.0.1, timeout is 2 seconds:
>> Packet sent with a source address of 10.1.7.7
>> !!!!!
>> Success rate is 100 percent (5/5), round-trip min/avg/max =
92/94/100 ms
>>
>>
>>
>> Message is... USE SEND-LABELS between IBGP when doing Inter-AS
VPNs with
>> dual interconnections!!!
>>
>> Best
>>
>> Andre
>>
>>
>>
>> On Fri, Oct 30, 2009 at 3:26 PM, Bryan Bartik
<[email protected]>
>> wrote:
>>>
>>> Hey guys,
>>>
>>> I think it depends on what the scenario is, and what the next-
hop is of
>>> the VPN route. For example, if you are doing MP-EBGP between
>>> route-reflectors in inter-AS scenario, the PE routers may need
labels for
>>> the PE routers in the other AS. If you do not have send-label
between the
>>> RRs and the PEs (IBGP) then the PE routers cannot properly tag
the packets.
>>>
>>> On Fri, Oct 30, 2009 at 9:36 AM, Shai Loufton <osl...@shai-
l.com> wrote:
>>>>
>>>> I am now actually on a proctor labs' 7200/ATM Rack now doing
the second
>>>> VOL II lab and I see exactly what you describe – it works with
just enabling
>>>> "send-label" on the ASBRs (and "set mpls-label" if there is a
route-map in
>>>> between).
>>>>
>>>>
>>>>
>>>> I cannot think of a reason of doing the LSP as a BGP LSP from
end to end
>>>> – can anyone else comment here about this also?
>>>>
>>>>
>>>>
>>>> BTW – thanks André Luiz Bernardes for helping me before …. – I
will do
>>>> the 1st lab tomorrow again – hopefully will understand it all
and all will
>>>> work eventually after I am done with it ….
>>>>
>>>>
>>>>
>>>>
>>>> Shai L
>>>>
>>>>
>>>>
>>>> From: [email protected]
>>>> [mailto:[email protected]] On Behalf Of Andr?
Luiz
>>>> Bernardes
>>>> Sent: Friday, October 30, 2009 4:17 PM
>>>> To: [email protected]
>>>> Subject: [OSL | CCIE_SP] BGP Labels, send or not to send....
>>>>
>>>>
>>>>
>>>> Hello guys
>>>>
>>>> I have this doubt here.. when configuring Inter-AS VPN we have
to build
>>>> an e2e label path to get VPN traffic flow between ISPs. Most of
the times we
>>>> are required to exchange loopbacks labels via IPv4 eBGP
sessions between ASs
>>>> since LDP is not allowed.
>>>>
>>>> Well... I have done this several times already on different
vendor's
>>>> wookbooks and that works fine just by configuring BGP send-
label feature
>>>> (and mpls set-label on route-maps) only on EBGP sessions. My
questions is
>>>> why worbook solutions always require configuring BGP label
distribuition
>>>> also for IBGP session? Is this just a best practice or is there
any
>>>> underlying issue that does not come up on workbook scenarios
due to reduced
>>>> topology...
>>>>
>>>> Thanks
>>>>
>>>> Andr'e
>>>>
>>>> _______________________________________________
>>>> For more information regarding industry leading CCIE Lab
training,
>>>> please visit www.ipexpert.com
>>>>
>>>
>>>
>>>
>>> --
>>> Bryan Bartik
>>> CCIE #23707 (R&S), CCNP
>>> Sr. Support Engineer - IPexpert, Inc.
>>> URL: http://www.IPexpert.com
>>
>> _______________________________________________
>> For more information regarding industry leading CCIE Lab
training, please
>> visit www.ipexpert.com
>>
>
>
> _______________________________________________
> For more information regarding industry leading CCIE Lab training,
please
> visit www.ipexpert.com
>
>
