I know this is a question that has been asked a million times over but here goes. I have two SDSL lines that I would like to load balance and/or provided redundant internet access. Now since these lines come from two different ISPs I have two blocks of IPs, one block for each line. Now I have servers that I would like to be able to provided public access using two different public IP's. Two public IP for each server, one from each ISP block, that will be port address translated to a single internal IP. This brings about many different problems, one which lies in the way I do DNS. At the moment if you talk to NS1 you will get public IPs for each server using ISP1's SDSL line and public IP block. If you talk to NS2 you will get public IPs for each server using ISP2's SDSL line and public IP block. Now I have tried to read and experiment with all the examples on the net I could find including the following links which are the main ones I came across several times. http://www.samag.com/documents/s=1824/sam0201h/0201h.htm http://www.linuxvirtualserver.org/~julian/nano.txt http://www.linuxvirtualserver.org/~julian/dgd-usage.txt Now with each of theses I run into a similar issue. That I will get to in a moment. I also tried buying a cheap solution, NexLand's ISBPro800, which in short does not work. NexLand is aware of the problems I have experienced, and have been working on a new firmware release for over two months now. I am not sure if they will get it to work or not. The only other choices of solutions I can buy are out of my price range at the moment. One is $5000, and the other starts at $7500.00. Here are links in order of pricing, http://www.sysmaster.com/products.htm http://www.fatpipeinc.com/ Now it is rumored that the second runs a modified flavor of Linux. So far the closest I have ever been able to get using Linux as a load balancing/redundant gateway router has some issues when it comes to routes existing in the route cache table. If you establish a connection to a server using a public IP from ISP1, and then go and establish a connection to the same server using a public IP from ISP2, you cannot until after the routing cache has been flushed. I tried playing around with the garbage collection and other params that are supposed to control the frequency that the routing cache is flushed. I was not able to reach a happy medium. I was talking with a engineer buddy of mine from Cisco and he said I needed proper aging to take place in my route cache. So if a new connection is attempted and an older different route exists in the routing cache, the older one will be dropped/removed to allow the new one in and traffic to flow. Makes sense, but I have no clue how to implement this, if it can be done outside of the kernel itself. So the bottom line is I can get it to work, providing that each and ever requests made to the server uses the same public IP from one or the other ISP. If there is a need to switch to the other line/ip then it will have to occur once the route has been cleared out of my routers cache, and possible the requesting machines cache as well. I am starting to think that this cannot be done properly with the current state of the linux kernel's multipath routing. Do I have to buy a >$5000.00 unit to do this? It seems that there are allot of people currently, and the more people switch to broadband I could see it only increasing, trying to do the same thing I am. So there really needs to be a solution for this. I will document a working solution if and when I come across one. Being that a couple companies are providing products that can do what I am attempting to, it seems this is something that the linux kernel hackers should look into adding or improving. If I had the proper knowledge of C/C++ and the linux kernel I would work on a solution myself. I am trying to envision a shell script or program outside of the kernel that could help out. But where I run into problems is for my program to be aware of each and every connection request and making a decision about the state of or content in the route cache without depleting the machine of it's resources. Is there anybody out there that has been able to get this to work? If so, how? What I am doing wrong? I can provide examples and anything needed. FYI I am currently using the Linux Router release of the 2.2 kernel, which is the linux router 2.9.8beta and is based on kernel 2.2.19. I think. I also attempted it with a newer kernel, 2.4.9-31 from Redhat, that was recompiled by me. Both lead me back to the same problem with the route cache. I am getting desperate and about ready to drop $5000.00, although I will not do it without kicking and screaming. Please help, anybody, I will try to make it up to you, so it is worth your time. Thank you in advance. -- Sincerely, William L. Thomson Jr. Support Group Obsidian-Studios Inc. 439 Amber Way Petaluma, Ca. 94952 Phone 707.766.9509 Fax 707.766.8989 http://www.obsidian-studios.com
