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load balancing on two ADSL connections

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by pfu

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I just got a second ADSL Internet connection.
I like to split the loading (users) between 2 ADSL now. Each ADSL use its own router, destinated as DHCP server and gateway .5 and .6 I have try splitting the users in two groups with two gateway orders 1) .5 then .6 2) .6 then .5
For some reason these gateway order doesn't affect which router it pick as the DHCP server(or GW) If first router is off, all computer will attached to the other router. Once the first router back on, all computer switch back to the first router as gateway.
Does the leased time from first router has any effect to this jumping back ?
If yes how could we reset this memory on the attaching computer ?
Currently I have to manually assign IP and GW and DNS on each group of computer in order to share the loading.
There should be so better ways to achieve this.
If anyone have some idea, please give me some assistance. Thanks a lot.
Philip

5 replies

by oz_media

Sorry, but his is not a forum for questions to be posted to.
You will get more accurate responses if you post with a point value to the Technical Q&A section of this site

by jim-h

As far as DCHP and Default gateways go your computer will not forward a DHCP request to the default gateway. With DHCP, the client will come online configured for DHCP and send out a "DHCPDISCOVER" Broadcast packet looking for an IP address from a Server. All DHCP Servers will respond that were within broadcast range and the client will accept what was assigned on a first come first serve basis.

Load balancing; I would move away from trying to load balance between two default GWs on each machine. If a single machine decides to change from Router-A to Router-B in the middle of a TCP/IP session then the source IP will suddenly change, assuming that your routers are using NAT, and this would confuse the connection if this happened. In mostcases your clients would just use the first Default GW in the list but I have see where a machine intermittently moves to the other without reason on Windows.

Let me know if this helped or if you need some other ideas for your dual DSL setup.
-Jim

by pfu

Hi Jim,
Thank you for you advice with very precise info on DHCP clients/server.
What I try to do is to share the Internet amount 2 ADSL connections with two rounters
With first come first serve base I guess a DHCP client has no choice on which DHCP server it could takes. Then I might have to settle on manually assigning the IP/GW/DNS on two groups of computers so that each groups will be connect through their assigned router. Right ?
Any alternative ?
Thanks
Philip

by jim-h

Hmmmmm, I do not know your full environment, but you should be able to get this to work for you:

1) Disable DHCP on both routers. Since the routers can?t communicate with each other over who did what last we will take them out o the DHCP Loop.
2) Enable a Server, or even just a service on a server always on, dedicated to DHCP for your LAN.

This should give you some options.
One option is that you could create two DHCP groups on your single DHCP Server. Then manually add in the MAC addresses of all your local computers alternating which group that they belong. If someone comes online that is not in the group you could then default them to Group-1 or Group-2.

Another option, probably easier in Linux or Unix systems, is to add somehomegrown scripts into DHCP ?deciding? When a DHCP packet comes in a script could check and verify Default-Gateway status, current users in either group, etc; for DHCP-Group-1 and DHCP-Group-2. With a setup like this if DSL-1 goes down then tell clients to renew the IP and then the DHCP Server could be smart enough to move all requests to the working one. Ideas can go on and on here for rules to use one or the other.

Do me a favor and post the progress.

Good Luck, hope it helps.
-Jim

by pfu

Jim,
I would temporary assign IP/GW/DNS to seperate the users in two groups.
In long run I will adopt your idea to have a single DHCP server using two scopes of IP.

Many thanks for your kind input.
Best Wishes, Philip

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