OSPF With MPLS IPVPN and Back Door Link

[ITGuy118]

We have Sites 1 and 2 connected to our MPLS Provider and also have a Backup link between Site 1 and 2 using a different provider for vendor redundancy. We are running OSPF between all the Sites and the MPLS all in Area 0.

We want all traffic to route through the MPLS and only use the Backup link in the event that the MPLS is down. I know that this is a common problem when using OSPF with MPLS and Back Door links and the answer has been to use a Sham Link. The issue we are running into is that our MPLS provider does not offer this configuration as they are a rather large provider and keep all services “standard”.

Another solution I found was to use BGP as the CE-PE protocol, but the MPLS is actually used to connect other business units regionally and our Regional team wants to keep the CE-PE protocol standard across all units.

I found a few forums with replies suggesting to use 2 processes and then redistribute or to redistribute everything so that it all comes up as E2 but many times the posters never confirm if this worked for them.

Has anyone gotten this working by not using Sham Links or BGP?

[paul driver]

Hello
I would say using a GRE or VL will just basically revert the to original setup where the LES was in Area 0 before changing it to non bb area which means when the mpls link comes up again the GRE/VL overlay via the LES will be the primary path and not the MPLS.

[MHM Cisco World]

NOTE:- the tunnel is pass through MPLS Core.
NOTE:- the tunnel source is interface of link direct connect to MPLS SP.

I already Test this solution, when shut the f2/1 in R1 the tunnel is down and show ip route show 5.5.5.5 via serial (interconnect direct) and when no shut f2/1 the tunnel is UP and R1 show ip orute show 5.5.5.5 via tunnel (which is via MPLS SP Core).

[paul driver]

Hello
I don’t have the opportunity to lab this one up myself at this present however in your lab @MHM Cisco World  you don’t show route advertisement between the other sites over the LES connection as/when the mpls link fails especailly interested in local routes from site 2 are these would be in area 0 

As for site 5 I would envisiaged its local networks would still travesre the les conection (west/east) and not south/north even when the mpls link is active, Also I am not convinced if this did work it would be a viable permanent solution for an estate as large as this.

[MHM Cisco World]

I confuse with site 2 and site 5 and my lab.

Can you more elaborate what want from me to test ?

I shut link to mpls and mo shut it and it wrok perfectly.

Do you want from add more router (site)?

[ITGuy118]

Just wanted to chime in and say Thank you for looking into this for me.

The Tunnel Solution may not work for us because we receive route advertisements from the MPLS cloud for other business units including our Regional Data Centers that host things like ERP, Email, etc... That's my fault for not mentioning it originally.

[paul driver]

Hello
The main issue is issue obviously you need to keep with using OSPF and try to traffic engineering so ospf prefers the mpls links that are advertising type 5 LSA over type 1,2,3 LSAs vai the LES connection

Now changing the les interconnection to a non bb area does address part of this problem but then you have a discontiguous area 0 for site 2/5 local routes and due to the inherent loop prevention OSPF has regards ABR LSA advertisement split horizon wont allow readvertisement of anything other than intra routes back into the backbone for a non backbone area as such site 2/5 local routes will be isolated.

[MHM Cisco World]

In my Lab I add LO in MPLS and advertise it to R1 (Site1) and R1 show the route from MPLS (LO 111.111.111.111) and see the the route from other site (5.5.5.5) via tunnel.
so I think GRE not effect route learn from MPLS

[MHM Cisco World]

Friend I think it better to try LAB by yourself see what happened and how OSPF MPLS GRE work together.

[ITGuy118]

Could you try your lab without the GRE and then redistribute connected from the site routers to see if that allows the MPLS to be preffered. I have a virtual lab setup but am not familiar with MPLS so im not sure how to re-create that.

Thanks

[MHM Cisco World]

I follow you and I see you ask about compare E with E of other OSPF process , So it will do lab BUT I want to ask are you interconnect between Site is appear as what ??

[ITGuy118]

They are comming up as O on the interconnect.

[MHM Cisco World]

the Lab is done and work BUT 
let explain the issue here, the network (Link) can not config under both process, so here we config network under OSPF10 (the OSPF process connect to MPLS SP) and then redistribute OPSF10 into OSPF15
so the prefix through interconnect will appear as E1/E2 (E1 or E2 depend on your config).
the idea is better than my idea of use GRE. 
in my lab I config LO 123.123.123.123/32 config it under OSPF10 and then redistribute it into OSPF15
when the MPLS SP link to R4 is down the R4 add this prefix into RIB as E2.
NOTE:- the redistribute with route-map I only redistribute the prefix need to send via interconnect, the Link between Site's and MPLS SP no need to redistribute it to other Process (prevent routing LOOP)

please ask any Q in your mind, may be there is some detail hidden for me.

[ITGuy118]

I had started exploring a similar option and this seems to makes sense. So you redistribute OSPF 10 into OSPF 15 on R4 and R5. Then what do i need to redistribute from OSPF 15 into OSPF 10? I understand about using a route-map but not sure what needs to be redistributed. Is this a physical lab or is this in Packet Tracer?

Thanks again for the help!

[MHM Cisco World]

NO this is GNS3, 
why use route-map?
we must prevent prefix learn in Site1 from MPLS and redistribute into other process and advertise to other Site2 to redistribute again into MPLS.
that it.

[paul driver]

Hello
As an alternative suppose could look into policy based routing, so to conditionally policy route traffic via the mpls and if/when fails occurs normal routing will take precedence?