The MPLS WG Archive

["Alexander Marhold" <alexander@marhold.at>]

Mike

Unfortunately "HUB and spoke" can be interpreted differently.

If the network need to emulate FR-behaviour you need 2 interfaces in 2
separate VRFs as Jim has mentioned.

If you only need get packets running between spoke sites to the HUB-CE in
order to do accounting, ---> then this also works with only one single
interface and a single vrf and a clever usage of the default route !

>From the SPOKEs to the hub you send the specific routes,
the CE on the hub site announces only the default route towards the MPLS/VPN
cloud
the Spoke-PEs in that way only receive the default route imported from the
HUB-vrf

then the Spoke PE sends all packets for other destinations on an LSP ( bound
to the default route) to the HUB-CE, which does a L3 lookup, finds the
destination address and sends the packet back to the hub-PE.
This one, using an LSP for the specific address forwards the packet to the
destination Spoke-CE.

In that way all packets between Spoke sites will enter the HUB-CE and can be
accounted.

(This is a tested configuration, usage can be for Bandwidth brokerage over
an MPLS/VPN network)

with best regards

Alexander


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-----Original Message-----
From: owner-mpls@UU.NET [mailto:owner-mpls@UU.NET]On Behalf Of jim
guichard
Sent: Friday, May 18, 2001 11:09 AM
To: Gould, Michael
Cc: mpls@UU.NET
Subject: Re: Unusual Hub-Spoke Configuration


Mike,

this type of topology allows all spoke to spoke communication to flow via a
hub site - this is just manipulation of the route-target. A simple example
of its usage is the need to deploy a firewall between spoke sites. Jim

At 09:57 18/05/2001 +0100, Gould, Michael wrote:
>In the JunOS MPLS Applications Guide 4.4, the example of a Hub-and-Spoke
>MPLS VPN configuration is very unusual.
>
>It states that: "For a hub-and-Spoke VPN topology to function properly,
>there must be two interfaces connecting the hub PE router to the hub CE
>router, and each interface must have its own VRF table on the PE router."
>
>It then goes on to describe a configuration where there are 2 VRF tables
for
>a single hub site.  One table imports only routes from the spoke sites and
>exports nothing.  The other table exports routes from the hub site and
>imports nothing.  The example is definitely not refering to a management
VPN
>and there is only one hub CE.
>
>Although it looks like this configuration would work, we have never needed
>more than one interface or VRF table per hub site.  Does anyone know the
>reason for this particular configuration?
>
>
>Mike Gould
>orchestream.com
>
>
>
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Jim Guichard CCIE #2069
Technical Leader EMEA

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