Re: BGP to OSPF Redistribution w/ Sham-Link

Marko,
I like to use the "magic" word for things that are either not fully
documented or not fully discussed in documentation or guides.
People tend to simplify things and do analogies. When you think
your analogy is good but it does not reflect the whole thing, you
might get burned.

I said that I've just seen a test case where the link does not come
up, even with the loopback published in BGP and not in OSPF.
So I don't fit in your rule.

And vrf-lite capability does change the checks performed by the routers
in the OSPF - MPLS integration. That's what I was pointing to.

-Carlos

Marko Milivojevic @ 11/10/2011 19:28 -0300 dixit:
> Actually... none of it is vrf-lite and there's no magic. For two-site
> configuration, I don't see the need for redistribution. If the
> sham-links wouldn't come up after a reload or a similar event, means
> someone missed a crucial (undocumented) step of needing to make sure
> those addresses are not advertised in OSPF. We've beaten that subject
> to a pulp few years back and on average every two-three months since.
> I'm kinda tired of discussing sham-links.
>
> --
> Marko Milivojevic - CCIE #18427 (SP R&S)
> Senior Technical Instructor - IPexpert
>
> On Tue, Oct 11, 2011 at 14:41, Carlos G Mendioroz <tron_at_huapi.ba.ar> wrote:
>> I would be careful.
>> I've just seen a test case where the sham link will not come up
>> without distributing BGP into OSPF. If you still have your lab setup,
>> do a full reload and check if it comes back up.
>> (sham link endpoints where /32 loopbacks, advertized by BGP inside vrf)
>>
>> Even though sham links behave like a "standard" point to point unnumbered
>> link inside the area x, there is nothing "standard" in them,
>> and plenty of MPLS magic, partially controlled by vrf-lite capability.
>>
>> -Carlos
>>
>> Yuri Bank @ 11/10/2011 15:53 -0300 dixit:
>>> Yeah it works fine without redistributing BGP into OSPF.
>>>
>>> My theory is that because the Sham-Link is up, LSAs are flooded and reach
>>> the CE without any problems.
>>>
>>> However, all of the labs, documentation etc show otherwise (redistribution
>>> of BGP into OSPF), which simply isn't necessary in my opinion. I'm just
>>> curious if anyone else has noticed this? Of course, if you aren't using a
>>> sham-link, redistribution of BGP into OSPF is necessary.
>>>
>>> -Yuri
>>>
>>> On Tue, Oct 11, 2011 at 11:23 AM, Marko Milivojevic
>>> <markom_at_ipexpert.com>wrote:
>>>
>>>> What happened when you labbed it up? Did it work? :-)
>>>>
>>>> --
>>>> Marko Milivojevic - CCIE #18427
>>>> Senior Technical Instructor - IPexpert
>>>>
>>>> FREE CCIE training: http://bit.ly/vLecture
>>>>
>>>> Mailto: markom_at_ipexpert.com
>>>> Telephone: +1.810.326.1444
>>>> Web: http://www.ipexpert.com/
>>>>
>>>> On Tue, Oct 11, 2011 at 11:09, Yuri Bank <yuribank_at_gmail.com> wrote:
>>>>> I'm curious if this is really necessary? I've done this in my lab and it
>>>>> seems to work fine. I understand that you MUST redistribute OSPF into
>>>>> BGP
>>>> on
>>>>> your PE, so that appropriate VPN labels are advertised to the remote PE.
>>>>> However, I see no reason to redistribute BGP into OSPF, since the LSAs
>>>> are
>>>>> getting advertised through the sham-link, and the CE routers will have a
>>>>> complete LinkState Database from that.
>>>>>
>>>>> Is there anything that I'm missing?
>>>>>
>>>>> -Yuri
>>>>>
>>>>>
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>> --
>> 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