Two Gateways?

mattreay said:
no load balancing router will be able to combine the speeds of your internet connections if you have 2 external ip addresses which is what usually happens if you are using two modem/routers. It is in the nature of TCP/IP that if must have a destination IP address and a source IP address, meaning one connection can only be from one router or the other. If you have two seperate TCP/IP connections then you a load balancing router should router one so the source IP is router 1 and the seconds so the source IP is router 2 giving you the full speed of each router per connection.
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Yes you can. You just need some kind of round robin dns system to distribute the requests to each modem. Zonedit works well for me. Look at their failover & Load Balancing services.
 
that's what i meant with a connection being from one router or the other. you can combine the speeds with 2 or more TCP/IP connections but you couldn't have the full combined through put with just one TCP/IP connection as one TCP/IP connection must come from one router or the other.

Zonedit's service works in that way, by sending the data for your dns name to one or the other of the modems, it couldn't split the packets between the modems unless that was shown as the source IP address to packets leaving and entering your network, in which case it would just be a load balancing NAT router
 
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the only way you could do it would be to add another NAT router after your ADSL modem/routers, this would allow you to have one external IP address but that would be pointless unless you could get your ISP to do it
 
mattreay said:
the only way you could do it would be to add another NAT router after your ADSL modem/routers, this would allow you to have one external IP address but that would be pointless unless you could get your ISP to do it
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This is incorrect.
 
The only way to combine multiple connections with a single TCP connection is bonding, which requires ISP support. No other "NAT routers" involved.
Load balancing will only give you the combined bandwidth of both with multiple TCP connections.

Dunno where the hell DNS comes into it, since it doesn't affect routing. :confused:
 
Could you explain yourself please Topgun?


I presumed adding a NAT router at your ISP's end of the connection would make that router the end point of TCP/IP Connections? Then again it would still have to route TCP/IP connections to one or the other of the modem/routers?

DNS has nothing to do with routing but can provide redudency by setting more than one IP address for a domain name.

EDIT: Appolgies, I've been talikng crap there, after doing some research. You're right, NAT wouldn't solve anything, is is possible to create a ppp connection that is split between two modems? This would give a single IP address and splittle the data between connections would be done lower down the connection on the OSI model? Not sure if this would work, it would probably require ISP support?
 
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sorry, went off topic sightly. try my original suggestion, set 2 static routes on your server to 0.0.0.0 and set the gateway to your 2 routers. If you give them equal metrics is sound destribute connections equally between the connections or set a higher metric if you have one less favoured connection. I think that should work.
 
If its a windows box, can you not add 2 default routes to each route?, the main and secondary interfaces on the box are specified with the "if" keyword, and the secondary route has a metric of 10, if the main interface goes down it'll drop out of the windows routing table, only problem is that the failover depends on the interface going down, it won't failover if there is a problem other than physical, past your router.. but its better than nothing.
 
Yea, think he's looking to switch paths based on CE-PE link failure unfortunately.

Do you know what routing protocols (if any) are supported by your routers?
 
setting a default route/default gateway is that same as setting a static route to 0.0.0.0 on windows you should be able to specify more than one default gateway on a computer by going on to properites of tcp/ip for a network card, you can also set a manual metric for each gateway
 
Sorry to bring this back up from the depths but it's exactly what I intend to achieve.

For windows to failover to the other gateway, will destination net unreachable from the router be sufficient for it to be considered dead?
 
we did it through the ISP, they supplied us with a cisco 1800 series router and bonded two connections together


works a treat
 
There's no real redundancy there though, if the isp has problems, both lines will fail.

I want to have automatic failover to another gateway.
 
Well you wont unless they run into problems, I'm saying that having two different ISP's is going to be better than your bonded solution.
 
Im pretty sure they run both the adsl connections on different circuits so yes I suppose in the event the ISP's whole network fails yes, we lose connection, which Is why we have fallback ISDN :P
 
To be honest, either you buy the kit to do this properly (and the cost isn't an issue) or you plug a different cable in when the first connection goes down.
 
ruffneck said:
Im pretty sure they run both the adsl connections on different circuits so yes I suppose in the event the ISP's whole network fails yes, we lose connection, which Is why we have fallback ISDN :P
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or the DSLAM at the exchange breaks, or their BT central...

that solution offers improved speed sure, but it offers very little reliability benefit..
 
I have a single linux gateway doing something similiar with a cable + adsl connection. A couple of cron scripts that check connectivity by pinging outside mean that if one goes down it will switch to the working one.
 
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