BGP design and multihoming

[prafuljaded]

Hi All,

I need to setup an internet connection running BGP multihomed to two different Service Providers,both running 9 Mbps .I have an option to use either one or two 7206 for this connection.All my setup is in a single location(rackspace)

My questions are

1) Is it better to use two 7206s and have IBGP configured between them ?

2) Suggest me the best way for in and out traffic of my Autonomous system( I want the traffic to be flowing fine even after one DS3 goes down,automatic switchover)

3) Suggest me some BGP design references and good practices

If you need any more info, let me know

Thank You

Praful

[arvenugopal]

hi,

1)7206 is a good choice will give a way for future groth also, use 2 routers run iBGP in between, i suggest to us Local preference to control the out going traffic. for incoming i suggest to advertise the supernet in both the routers. and specific subnets as you wish (always longest prefix will be prefered).

http://www.cisco.com/en/US/partner/tech/tk365/technologies_tech_note09186a00800c95bb.shtml

[prafuljaded]

Hi Venu,

Thanx for your reply.Lets say for example,I already have a 168.1.1.0/24 IP space from ISP A and prefer not to have any public IP sapce from ISP B.So obviously ISP A will have shortest path to my network.So can I advertise 168.1.1.0/24 and more specific route 168.1.1.0/25 thru ISP A and 168.1.1.128/25 thru ISP B in agreement with them ?

Is there redundany if one of my 9 Mbps fract.DS3 goes down ?

Praful

[joe.cornelson]

Hello,

With three routers, (the other could be a 2620 or higher), you could use iBGP multipath load sharing for outbound traffic. Use med to balance traffic that enters your network.

[jrahm]

You could load-share outbound without the third router using GLBP.

Unless you have a need to run iBGP between the two, it's much simpler to configure a gateway of last resort on each 7206 to the other, that way all outbound traffic will flow to the other 7206 if its particular ISP link is down.

[ravirepaka]

Hi Praful,

If you are still looking for a solution ,please provide the information like..are you looking for load balancing/load sharing between ISPs ? or just the link failover?

[prafuljaded]

Hi Ravi,

I have setup a single BGP ISP connection now. And want to go for load balancing, outbound and inbound traffic when I get the second one soon. I have a /24 Public IP space from my ISP1.Let me know how to go about it.

Praful

[prafuljaded]

Looks like my post is lost out here. Any ideas about it , please ?

Praful

[cdfowlie]

You have mentioned in a previous post advertising a more specific route to one provider. Keep in mind that routers will always choose the most specific prefix first. So if you advertise 192.168.1.0/24 to provider A and 192.168.1.0/25 AND 192.168.1.0/24 to provider B, all traffic for 192.168.1.0 - 192.168.127.255 will come in via provider B.

If all prefix lengths are equal, the BGP best-path selection process will be used to determine utilization.

Using 2 routers with IBGP gives you physical redundancy. You can easily use a single router with 2 EBGP peers. Just make sure to crank up your DRAM:) This is your choice based on your own business plan / cost model, etc.

My suggestion is to take the space provided, advertise it to both providers with no frills and monitor the link usage from each. To the rest of the world, the route will be originating from your ASN, so it doesn't matter which of your ISP's allocated the space originally. If you find that default values don't give you the load-balancing you need, THEN start to tweak.

Don't try to fix it if it's not broken...

Can't tell if it's broken if you don't put it together first...

Let me know if I can help further

HTH

-Colin