[j-nsp] internal BGP necessary ?

[Piotr]

There is some problem with upload diagram, even small, here is link:

http://pokazywarka.pl/mg6gtf/

[url=http://pokazywarka.pl/mg6gtf/]diagram[/url]

W dniu 2013-03-24 11:36, Piotr pisze:
> Hi
>
> I attached diagram. I have to connect together two different companies.
> They have ethernet leased lines, so i can use bgp on private AS numbers.
> Each have own OSPF. There is max 1k routes in igp. In this moment i use
> only ebgp, i removed ibgp. I made redistrubutions ospf-(e)bgp and
> (e)bgp-ospf on A1 A2 B1 B2,  i have also tags against mutual
> redistributions. Ebgp has 200 ad on cisco, For now all works, but first
> time without ibgp. I'm affraid about some problems like loops..
>
> thanks for any advice or notice
> regards,
> Piotr
>
>
> W dniu 2013-03-23 22:29, Patrick Okui pisze:
>> Hi Piotr,
>>
>> On  23-Mar-2013 16:13:18 (+0200), Piotr wrote:
>>> I have to connect two networks via bgp, both have own ospf area0, there
>>> are 2 points od redistribution between BGP and OSPF. We use med to have
>>> symmetry, because Junipers must work in flow based (ipsec).
>>
>> Probably a small ascii diagram would help in this case. If you're using
>> MED then these two networks are two separate ASes correct? Juniper in
>> one, Cisco in another?
>>
>>> When we set on cisco  default AD, on juniper we change bgp ad to 20 (
>>
>> The default AD of eBGP in Cisco is 20, but of iBGP is 200. However,
>> Cisco by default will wait to see a route in the IGP before installing
>> it into BGP. I usually set both to 200 (and turn off synchronisation)
>> thusly:
>>
>> router bgp NN
>>    distance bgp 200 200 200
>>    no synchronisation
>>
>> You may also want to set bgp deterministic-med on the cisco side to
>> match how most other vendors treat MED.
>>
>>> like in Cisco) juniper prefer routes from ibgp and there is a problem
>>> with redistribution between ospf and ebgp because there is no prefix
>>> from ospf in rib.
>>
>> one of BGP's first rules is reachability to the next hop. If BGP can't
>> reach the next hop it will drop the prefix advertisment. Your IGP has to
>> guarantee this.
>>
>>>
>>> I think that when i remove internal bgp session there should be ok, in
>>> rib there will be prefixes only from ospf so there will be no problem
>>> wirh redistribution? There are some disadvantages when there is no
>>> ibgp ?
>>
>> I think my first question is ... why are you redistributing in the first
>> place? iBGP will handle more prefixes than any IGP - so usually you just
>> want to carry your infrastructure/interface/link prefixes in the IGP and
>> everything else in BGP. If you go down this route, then a full iBGP
>> mesh[*] between BGP speakers is required to avoid loops.
>>
>> Again, it's not easy to guess what you're trying to achieve without a
>> diagram.
>>
>> Will OBrien's comments above give hints on getting redistribution
>> working but then again, we're all shooting in the dark.
>>
>> --
>> patrick
>>
>> [*] or a route reflector or ...
>>
>
>
>
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