Internet access by MPLS connectivity

[ajay kondapalli]

Hi,

Can any one explain me , how the packets destined for public internet are routed 

if we have MPLS connectivity. generally ISP route packets to our corporate offices based on labels between our offices. (H.O to branches).

But if we browse public internet sites like google or facebook, how are the routing policies are implemented in enterpise networks.

Does our ISP do that by RD and RT values purely or is there other mechanisam to handle that ?

Do we implement a default route to all unknown destinations towards ISP ? How is it done in MPLS?

Thanks,

Ajay

[vmiller]

From my own experience, we had internet facing routers in our datacenters, and a nationwide Public MPLS network. We advertised the default through our RD.

I don't imagine it would be any different if the MPLS provider was also your ISP. They could inject the default for the PE's to advertise.

For your remote locations, all they really need is a default out, The cloud would make all the choices. More specifcs for your enterprise RD, and default to the internet.

[ajay kondapalli]

So I understand that  if we have MPLS provider and our ISP for internet as same , they inject a default route into our CE , sothat we can access internet. Coming to our corporate remote locations, they route our packets based on labels in mpls domain.

We need to advertise our private routes to the PE routers using EBGP so that they maintain our routes in a separate VRFs  assign labels and route packets. 

Am I correct or is there any thing to be corrected ? 

Thanks,

Ajay

[Giuseppe Larosa]

Hello Ajay,

a default route can be sent out the PE node that is  connected to the internet gateway as a VPNv4 route and installed in all remote PE nodes and passed to remote site CE nodes.

Other options are possible: internet access can be given on a different subinterface ( Vlan based or a different DLCI or ATM VCC) in that case the default route is not present in the VPNv4 routes and can be part of a different VRF or in the global routing table.

MPLS L3 VPN forwarding uses two labels the external label is provided by LDP or RSVP TE for the LSP with destination the loopback address of remote PE, inner label is provided by MP BGP by remote PE itself.

A VPN label can be associated to a 0/0 route when the internet access is within the VRF as any other prefix.

Hope to help

Giuseppe