Designing for two WAN (non-Internet) links

[fahim]

Hi Guys,

I have tried to make the attached diagram as simple as I could. The scenario is:

Till recently we had only one ISP1 giving us intrasite MPLS VPN connectivity. We ran into major support issues with them and have hence decided to bring in a second ISP2 providing us alternative MPLS VPN links to three of our Site offices spread across two continents. We are sitting in say: Site 1.

At all the three sites, the MPLS links terminate on ISP administered routers (1800 ciscos).

Till now, it was simple, the ethernet interface used to come in and terminate on our L3 core swiitches but the problem starts now when second ISP2 will terminate his connections.

Is there a way I can utilise both the links in a load balancing manner rather than keeping one link purely in the passive way?

Which all routing routers will I have to bring into picture? Can GLBP be of help here? I need to minimise my dependence on this I have to involve ISP1 for they take months to even ad a summarised route onto their network when we raise a request to them.

ISP2 will hopefully be more proactive and they are even willing to administer the 'ISP2 Router1' which will eventually sit in our premises.

Pls advise

[fahim]

Hi Mohamed

I am a bit stuck at two issues.

1. If one of the provider maintains that he will provide me L2 MPLS at one of the sites, can I make him participate in BGP between CE and PE routers?

2. Just by enabling dual paths from each of my L3 switches and running BGP, would I accomplish load sharing?

3. What all is needed to enable OSPF on my internal side? Is there designing aspect involed.

Would love to recieve that 'helpful' link you've mentioned.

Regards

[Mohamed Sobair]

Hi Fahim,

1. IF the provider maintains he will provide L2VPN serice (Overlay VPN Model), then he cant participate in your L3 routing.

2. Enabling Dual Path from your Core Switches besides BGP (Assuming now the LAN Interfaces of ur ISP routers are accessible from each) would achieve Loadsharing, By doing So, you will ensure redundancy and loadsharing from the Core Switches as well as from the ISP routers. Dividing your Networks to be advertised to the rest of the Sites in Segments, and prefer some over another on Each GW router would achieve loadsharing.

3. On your Interneal LAN, you will need to have the CORE Switches part of AREA0 (Backbone) Area, the use of Stub routers and summarizes the Routes at AREAO would limit the number of route exchanged. The number of routers per Area and neighbors is based on lots of factors and based on your previous posted diagram, you dont have to worry about that. Another Note, the Area border router keeps state and copy of each linkstate database for every area, so it requires more CPU and memory resources.

Here is the OSPF deign Guide for ur reference:

http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml#t40

Attache bellow is "Loadsharing with BGP" when Multihomed to two different Service providers.

HTH

Mohamed