Question

Can I do load balancing with redundancy?

Load balancing, Redundancy, Networking, Routing and switching, ISPs, IP, OER, Routers

I have two links with different ISPs, and both links (512Kbps) are terminated on separate Cisco routers (2811). Currently, we are using one link, and another link is new. I want to do load sharing and redundancy between them. Right now I am not using BGP (routers are configured in simple manner). My present network scenario is like this:

Internet Ri (ISP 1)-- Layer 3 switch (working here as a simple switch)---Firewall 1 (Cisco ASA5510)--Firewall 2 (Cisco ASA5510)---Lan.

On firewall 1 remote and site-to-site VPN configured, one DMZ.
My LAN is in the 172.16.1.xx series, DMZ is in 172.16.4.10, and after 172.16.1.30 is using for desktop, 192.168.x.x is my management IP.

Right now I have another Internet link (512 kbps) from a different ISP.

Please advise how I can do load balancing with redundancy. I was trying OER but not successfully due to the IOs image (c2800nm-ipbasek9-mz.124-11.T.bin) and ISPs AS. Please help me with any idea on the OER or any solution. If possible, please send me a sample configuration.

If you need any other info, please let me know.

The best answer to this is to use something called Border Gateway Protocol or BGP along with two providers that will support this with one another. Essentially, you would have two separtae providers that would provide you with bandwidth, but you would only have one range of IP addresses---which are used by both providers to send you traffic.

The challenge with this is that it costs to do this. Each month for the bandwidth and for the extra charges to do BGP. Plus the routers are expensive (the 2811's don't do BGP as far as I know)

Another thing you can do is to bring the bandwidth in and and create a second set of servers to preform any services you provide on the second ISP's network. This will require either Round Robin DNS or a application layer load balancer, for example one I've used is a Web Server Director Pro from Radware.

In Round Robin DNS you essentially create a second set of A record DNS entries for all the hosts that are provideing services on the internet. For example, www.yourdomain.com might have two A records... one on one ISP and one on another ISP's IP address space. DNS by default "takes turns" handing this out. If you should take this route, be sure and set the TTL very low (2-5 minutes) on these records so that if a ISP link goes down you minimize the amount of time a "unoperational" address is cached on DNS servers on the internet.

The other possibility I mentioned was a application layer load balancer, like a Web Server Director Pro. This is probably the better solution because you can do more than just balance the load. You can detect failures of a application or server as well as shape traffic-- for example if one your pipes are smaller than the other one. Additionally, it allows you to scale your servers horizontally to 2, 3, 4, or more servers providing the same services, much like the "big boys".

The challenges you will have is that you will have to chose where your client internet traffic comes from without BGP since the response back to a client request will be directed back to the ISP it comes from.