General question about use Cisco 1841 as the ISP load balancer

Difan Zhao · ‎01-19-2010

Greetings experts!

I work for a company who provides internet services to hotels. We recently have a new client. They have two ISP connections, one for hotel guests and another for hotel admin network. Currently these two links are independent and separate. They ask me if it's possible to make both redundent to each other, so normally, traffic sourced from admin network will be sent out from ISP1 link and traffic sourced from guest side will use ISP2 link. And when one link is down, all traffic go on another link.

They also want public IP on the admin gateway (which is an ASA) and don't want any NAT in the process.

So here is my thought:

Let's say the router has 4 interfaces. First two are for connection to two ISPs and let's say their IP ranges are A and B. Guest side gateway will be on network C and admin ASA will be on network D and they will be connected on the rest two ports of the router.

I think in this case, both ISP1 and ISP2 have to aware of both network C and D, correct? Then in case one link is down, another link can pickup and still route for both C and D. We also want, in normal case, traffic destinated to admin ASA will always use link1/A and traffic destinated to guest side gateway will always use link2/B. Is that something ISP can easily done? Will that cost a lot? I will for sure check with ISP but just want to have a basic idea how much it will cost.

I also googled and I see solution of using BGP. I think they mean run the BGP on the 1841 router and tell the both ISPs that it has network C and D directly connected. However will I be able to configure BGP to tell both ISPs that when both links are up, always use link1 for admin ASA traffic and link2 for guest side traffic? If possible, can anybody please paste a sample config? Is this using BGP ease configuration for the ISP and save cost?

Hotel also asks if 1841 is good enough for it because they have a spare one. What do you think?

Any suggestions are welcome! If my solution is not a good one, let me know if there is a better alternative. Thank you!

Difan

Ganesh Hariharan · ‎01-19-2010

Hi Difan,

Load balancing between two ISP can achived in different ways check out the below link for IOS based load bacling which is done in router using NAT but you dont want NAT in your network.

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_configuration_example09186a0080950834.shtml

If not using NAT then i would suggest you go with BGP configuration along with route map for load balacning the internal subnets.

HTH

Regards

Ganesh.H

Difan Zhao · ‎01-20-2010

Hey Ganesh,

Thank you for the quick reply!

No we can't use NAT becasue our service contract require us to give hotel public IPs and go directly to internet... So sounds like the BGP is the only way. I have no experience with BGP. I only learned about it in school. Can you find me a link and show me how to configure it? Thank you!

Difan

Ganesh Hariharan · ‎01-20-2010

Hey Ganesh,
Thank you for the quick reply!
No
we can't use NAT becasue our service contract require us to give hotel
public IPs and go directly to internet... So sounds like the BGP is the
only way. I have no experience with BGP. I only learned about it in
school. Can you find me a link and show me how to configure it? Thank
you!
Difan

Hi Diffan,

Check out the link which is consists of fully configuration of BGP with all commands hope that helps you to solve the query !!

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfbgp.html

If helpful do rate the valauable post.

Regards

Ganesh.H

Richard Burts · ‎01-21-2010

Difan

In this situation you need to consider both how you will route outbound traffic and how response traffic will get back to you. Using BGP addresses the part about how response traffic will get back to you. You need a different approach to handle how you will route outbound traffic. Probably Policy Based Routing would be the optimum solution for outbound traffic so that admin traffic goes out the appropriate connection and guest traffic goes out its connection.

Using BGP can become complicated. Here are a couple of aspects that you should consider:

- how large are the address spaces for admin and for guest users? If they are small (in general less than a /24) many ISPs will not propagate advertisement of small address spaces.

- how did your customer get the address spaces? If they have provider independent addresses then advertising both address spaces to both ISPs is fine. But if their addresses to assigned to them by their providers then advertising both addresses to both providers is problematic.

We do not have enough information to answer the question of whether an 1841 would be adequate for your task. What kind of connection do they have to the ISPs? What is the volume of traffic that needs to be sent?

HTH

Rick

HTH

Rick