Using BGP to connect 6 sites in full meshed VPLS network

Unanswered Question
Jun 4th, 2009

We currently have 6 sites in hub-spoke topology, with FR for primary connection on primary router and ISDN for backup link on secondary router at each site. The network will change the primary network to fully-meshed MAN, and the secondary network will be DSL point-to-point connections (extended star topology). I would like to have:

1. every router in primary network act as gateway for its peers, to pass on all its WAN routes to other sites;

2. secondary network is passive under normal circumstance;

3. if all connections in primary network for one site went down, then the secondary router at that site will become active and automatically pass the routes to that primary router.

Is it achievable? Is there any examples available that I could have a look?

I have this problem too.
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Giuseppe Larosa Thu, 06/04/2009 - 01:24

Hello Tony,

I would use an IGP on the full mesh MAN service BGP would require to configure a lot of sessions.

if using BGP sessions a full mesh is:

6*5/2 = 15 sessions

2) routing on secondary network should use routes with greater AD examples:

floating static routes using DSL dialer interfaces as next-hop.

are these DSL links mapped to a VPN?

otherwise you need to build VPNs (ipsec recommended for this)

3)

a possible tool for this is dialer-watch or it can be enough to use the floating static routes with dialer interfaces as next-hops.

see

http://www.cisco.com/en/US/tech/tk801/tk133/technologies_tech_note09186a008009457d.shtml#dw_operation

But I think floating static routes could be enough

Hope to help

Giuseppe

yanzhu Thu, 06/04/2009 - 15:31

Hello Giuseppe,

Thanks for reply. Regarding using IGP (EIGRP or OSPF) instead of BGP, Is there any examples available?

The DSL link was delivered via Ethernet port (PPPoE), so no dialer required. Floating static routes is a good idea. I was thinking of making the secondary links the least favorite routes by using administrative distance at each site, which uses the same routing protocol as primary routers at same site. Maybe I should think again on this case...

Tony

Giuseppe Larosa Thu, 06/04/2009 - 23:57

Hello Tony,

the VPLS provides a virtual lan segment configuration with an IGP is simple:

router ospf process-id

network 10.10.10.0 0.0.0.255 area 0

you need to include a network statement for the IP subnet used in the VPLS MAN segment.

This is one of the reasons that makes VPLS services attractive for enterprises.

Additional network commands are needed to advertise the ip prefixes internal to

each side.

you should add another site with an IGP you don't need to modify the configuration of the already existing sites with BGP you need to modify all the sites to accomodate the new site.

You shouldn't have problems of scalability until the number of sites is less then 50.

I agree floating static routes can be a solution for the backup/secondary network

Hope to help

Giuseppe

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