[c-nsp] BGP Architecture Question

[Olav Langeland]

> -----Original Message-----
> From: Christopher Martinsen [mailto:cmartinsen at viatraining.com] 
> Sent: 17. november 2004 00:47
> To: cisco-nsp
> Subject: [c-nsp] BGP Architecture Question
> 
> I am going to be setting up BGP for my company.
> 
> I have secured two T1 circuits, each from different ISP's.
> I have secured an AS number for my organization.
> I have secured a full class C address space.
> 
> The question that I have is about architecture.
> 
> I will have each T1 going into a seperate router. I have
> one Cisco 2621 and one Cisco 2621XM.
> 
> I believe that with BGP the incoming traffic will be somewhat
> load balanced as well as connectivity for my organization will
> be redundant should one of the circuit go down.
> 
> I want to know the best way to architect the LAN side of the 
> connection. I will have:
> 
> 	T1		T1
> 	\		/
> 	 \	       /
> 	 Router	     Router
> 	    \	     /
> 	      Switch 	
> 		|
> 	    PIX Firewall
> 	    
> If I put a switch between the firewall and routers. How can I set the 
> outbound traffic to be load balanced?
> 
> I'm not sure what options are available to me. I'm hoping 
> that someone can provide me with some options and insights 
> on the best way to architect this.
> 
> Thanks,
> 
> Chris

Here are some links from cisco.com about BGP, second one is a
configuration example for multihoming (which is what you want):
http://www.cisco.com/pcgi-bin/Support/PSP/psp_view.pl?p=Internetworking:
BGP
http://www.cisco.com/warp/public/459/27.html

Internal setup can be done with HSRP on the LAN interfaces on your
routers, and iBGP between your routers. This will mean that some traffic
goes twice in your network since it can go Firewall -> HSRP IP to
Router1 -> iBGP decides it should go out via second router -> Router2 ->
Internet. But it will give you redundancy, if Router1 goes down the HSRP
is taken over by Router2 and traffic will continue to flow. 

If this is acceptable depends on your network and how much traffic you
have, but it's a decent design solution. For doing more with load
sharing on outbound traffic there are several ways of achieving this
including localpref
(http://www.cisco.com/en/US/tech/tk365/tk80/technologies_configuration_e
xample09186a00800945bf.shtml#conf5). 


Regards,
Olav Langeland