Re: Loop Prevention MPLS VPN

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
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
>
>
>
>
>
>

--
Blogs and organic groups at http://www.ccie.net