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Old 04-19-2010, 06:14 PM   #1
Akdor 1154
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Registered: Mar 2008
Distribution: Xubuntu, Sidux, Debian
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Question Automatic Route Table Entries

Hi all,

I've got the following setup working nicely, with my linux laptop working as a brilliant wireless bridge while keeping my subnetwork with its own dhcp and dns separate from the rest of the network:
|     Internet   |
|                |
 |  | router |---[other devices]  |
 |  +--------+                    |
 |     |    |
 |     |                          |
 |     |[wifi]      +-------------+--------------------+
 |     +------------|  laptop     |     |
 +------------------+-------------+                    |
                    |   |    +-----------------+       |
                    |   +----| ethernet switch |       |
                    |        +-----------------+       |
                    |          |          |            |
                    | +-------------+   +--------+     |
                    | |    Debian   |   | Gaming |     |
                    | |    Server   |   |   PC   |     |
                    | +-------------+   +--------+     |
The laptop is routing using iptables. Each side, given a routing table entry to the other subnet via the laptop, can see the other subnet no worries. Now, thanks to my control over dhcp on the .0.0 side via my server, I can pass the laptop's IP as the default gateway to everything in my (the subnet and all these routes are configured automatically. Shabang, internet ahoy! The problem comes from when someone on the subnet (i.e. any wifi clients) wants to access the ...0.0 side. If a route to via the laptop is added, it works fine - however this is a pain in the arse. I have friends with macbooks where it's tedious at best, and at worst my symbian wifi phone doesn't even ALLOW me to configure the routing table, leaving it isolated from all my servery goodness.
Scoping around the internets, I came across which seems to do what I've wanted - however I can't get it to work. I'm using icmpush on the laptop to create packets for prototyping my configuration, but nothing seems to actually change how e.g. my symbian phone can absolutely not see
One thing I am looking at with interest is how routers (e.g. my laptop) are meant to add themselves to the multicast group - do I need to configure this before things will start to route through it automatically?

Other than that I'm out of ideas, so alternate plans for automatic routes from to are welcome.

I should also mention that I have no access to the wifi router so I can't add static routes there.
The above setup is at the limits of my ability at the moment - obviously expanding these limits is OK but just keep in mind I'm no network engineer.

Thanks kindly,
Old 04-21-2010, 11:06 PM   #2
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Is your phone configured to use router discovery ? ... probably not likely
Old 04-26-2010, 04:23 PM   #3
Registered: Mar 2009
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Just configure the default router with the route, as well as sending the traffic to your laptop it will use ICMP redirect to inform the hosts to use the laptop.

Originally Posted by Akdor 1154 View Post
The laptop is routing using iptables.
Iptables does not do routing, and nothing in your question requires the use of iptables on the laptop.

On a point of terminology, your laptop is not a wireless bridge, it is a router.


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