mpls P routers and default routes

[jonathan johnson]

Hi,

I was hoping for some advise on the best practice for the following scenario.

We have a MPLS BGP free core that runs OSPF for the advertisement of the LSR ip addresses.  I have the following configured (default-information originate) on one of the P routers so that we have a default route propagated to all P routers so that we cab reach it for management purposes etc.

Having the default-information originate has an unintended result of pushing a default route to the PE when we loose the eBGP service on the PE. The replacement default route should come from one of the other PE devices 

Are we best to remove the default-information originate and have some statics in place for routing back to the management IP blocks or alternatively we can configure a distribute-list on the PE to stop the 0.0.0.0 route from entering the PE devices.

What is considered the best way to not have a default route being learnt by the PE via OSPF ?

Thanks,

Jonno

[Hector Gustavo Serrano Gutierrez]

Hi Jonno,

If your management IP block is part of your Global Routing Table, why not just advertise it in OSPF?

Why a default route is needed?

With "MPLS BGP free core", I assume you are doing MPLS L3 VPN which means all 'customers' connects to the PEs in a VRF.

Hector

[jonathan johnson]

Thanks Hector. 

The default route isn't really required and one plan is to remove it and do as you mentioned with adding the management IP's.  But since I don't redistribute statics at the moment, I wanted to get some opinions on what others are doing before going down that path.

Thanks again for you input.

[Hector Gustavo Serrano Gutierrez]

Hi Jonno,

For your MPLS L3 VPN scenario, if you want to be able to reach all P and PE Routers, then you should have your management IP block in the Global Routing Table (Global RIB). Sounds like you already have that.

Not sure why you are following the "advertising default route" path. You can just advertise the management IP block into OSPF for the Global RIB. If you have some other device connecting to your Core that doesn't have OSPF enabled, then you can just redistribute some specific static routes into OSPF.

From your initial description I understand that the other default routes are being injected into your core in the Global RIB and not in any 'customer' VRF on the PEs, is that correct?

Note that using 'distribute-list' to block a default route will block ALL default routes, including the desired one.

Just my 2 cents.

Regards.