Re: Loop Prevention MPLS VPN

Yes Emmanuel. I actually opted to do that. I threw this out to see if there
alternative methods of doing this. So far I haven't come up with any besides
the using a distribute-list. Say there was a requirement to have the route
remain available in case the the MPLS path through the core or PE-2 was
unavailable, i'd lean towards using "distance" I suppose. Any thanks for
responding man.

On Mon, Nov 29, 2010 at 1:42 PM, Emmanuel Aramide <earamide_at_gmail.com>wrote:

> Hi,
>
> If I understand this correctly; PE3 is the next hop for the non-OSPF route
> you mention right? So under normal operation, PE1 and PE2 should see the
> route ...say x.y.z.1/24 via PE3 and you also want to redistribute the route
> to CE1.
>
> Your situation is that PE1 and PE2 are relearning x.y.z.1/24 back from CE1
> and they obviously prefer OSPF, thus causing a race condition.
>
> To fix this - block x.y.z.1/24 from being learnt from CE1. See below;
>
> !
> access-list 2 deny x.y.z.0 0.0.0.255
> access-list 2 permit any
> !
> router ospf 2 vrf VPN
> distribute-list 2 in
> redistribute bgp 100 subnets
> !
> router bgp 100
> add ipv4 vrf VPN
> redistribute ospf 2
> !
> etc etc
>
> Hope this helps.
>
> Regards
>
> Emmanuel
>
>
> On 29 November 2010 16:47, <iosluver_at_gmail.com> wrote:
>
>> Hi Group,
>>
>> Given the following:
>>
>> CE2
>> |
>> | OSPF
>> |
>> PE-3
>> |
>> |
>> |
>> |
>> MPLS Core
>> |
>> |
>> |
>> |
>> PE-1-----MPLS------PE2
>> | |
>> | |
>> | |
>> | |
>> |------ CE-1 ---------|
>>
>> mBGP is configured as follows:
>>
>> PE-1---- PE-3
>> PE-1---- PE-2
>> PE-2---- PE-3
>>
>>
>> Also assume OSPF process between the CE devices & the PEs are
>> redistributed
>> into BGP & vice versa. So VPN routes are learnt by both CE routers so
>> end-to-end connectivity within the VRF has been achieved
>> The OSPF process within the VRF does not run between PE-1 & PE-2 so a loop
>> could be created when routes learnt from PE-3 are redistributed to the VRF
>> OSPF
>> process.
>> Now suppose PE-3 has a second interface that is not running OSPF within
>> the VRF
>> & that interface is redistributed into both the OSPF process with CE2 &
>> the
>> mBGP to PE1- & PE-2. This new route will be prefered via OSPF by PE-1 &
>> PE-2.
>> Can someone please indicate what methods & approaches they would use to
>> filter
>> the redistributed route?
>>
>> Thanks in advance
>>
>>
>> PE-1 & PE-2 both learn the
>>
>>
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> --

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Received on Mon Nov 29 2010 - 14:38:51 ART