[clug] A routing question

David Tulloh david at tulloh.id.au
Wed Apr 18 23:44:37 GMT 2007

I've helped friends play this game before.  Our situation sounded 
similar, we were in the residential colleges and all outgoing traffic 
was charged (at over 30c/mb).  On the other hand the university gave us 
free traffic and we had an open connection to the university.  By 
playing bouncing games we were able to route through the university 
cache or directly out to the internet.

Assuming you don't have access to the routers I don't think that you can 
do this using standard IP routing.  I think that the easiest way to do 
it is to set up a proxy server on the middle computer, so it does the 
external requests on your behalf.  A http proxy server is fairly easy to 
find but if you want a lot of different ports you could try playing with 
socks.  I'd also suggest some fairly strict blocking rules to stop other 
people jumping through your proxy.

If you want a specific site like a game server you can set up a tunnel 
using ssh, the manual explains how to do it fairly well.

A final warning, the ANU monitors traffic levels from all computers and 
as soon as your traffic starts to go above the normal levels they will 
pay you a visit.  They have all seen these tricks done many times before.


Kim Holburn wrote:
> It really depends on what sort of routers you have and how much you 
> control them.
> The simplest way would probably be to remove the A to B link.  What do 
> you need it for anyway?
> Make all the machines on subnet A use the router that handles A to C.  
> Tell the A to C router that subnet B traffic goes to the router 
> handing C to B.  On subnet B tell the router that to find subnet A go 
> the the router handing B to C.
> On 2007/Apr/18, at 3:54 PM, Christopher Zhang wrote:
>> Hi list,
>> Say if the connections from subnet A to B are throttled down, but the 
>> connections from subnet A to C and from subnet B to C aren't. The way 
>> the connections are throttled is by applying rules on the default 
>> gateways of subnets A and B.
>> Is there a way to speed up the connections from subnet A to B?
>> The closest idea I can think of is to setup a gateway within subnet 
>> A, let's call it D. Setup a host in subnet C, let's call it E, and 
>> finally another gateway in subnet B, and call it F.
>> The idea is to route all traffic from subnet A to C, then bounce it 
>> off C to B. Since the connections from A to C and B to C are fast, 
>> this effectively increases speed from A to B. So instead of using the 
>> default gateways for subnet A and B, we can use our own new gateway 
>> D, then somehow pipe all traffic to E, and then from E pipe all 
>> traffic to our new gateway F in subnet B.
>> The reason this increases the speed from subnet A to B is that the 
>> connection is unthrottled from subnet A to C, and from subnet C to B.
>> Eventually this is like a man in the middle setup, in subnet A, tell 
>> all machines to use D as the default gateway. What D does is to 
>> forward to the traffic to E, D still uses the real default gateway 
>> for subnet A to do that however since this connection is to host E in 
>> an unaffected subnet, the connection is fast. Then E forwards 
>> whatever is forwarded to it to F, if we tell all computers to use F 
>> in subnet B, the traffic will reach any host fin subnet B, without 
>> any speed loss.
>> It is easy to setup D as a gateway and route traffic through it, but 
>> how can I tell D to route the traffic to E (in subnet C) and from E 
>> route all traffic to F (in subnet B)? I cannot tell D to use E as the 
>> default gateway since they are on different subnets. If I use 
>> iptables to forward the traffic, the packet will lose the original 
>> header which means the reverse won't come through.
>> Maybe a tunnel needs to be setup, but I have no idea how to do that, 
>> does anyone have better ideas?
>> Thanks
>> Chris
>> --linux mailing list
>> linux at lists.samba.org
>> https://lists.samba.org/mailman/listinfo/linux
> -- 
> Kim Holburn
> IT Network & Security Consultant
> Ph: +39 06 855 4294  M: +39 3494957443
> mailto:kim at holburn.net  aim://kimholburn
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> Democracy imposed from without is the severest form of tyranny.
>                           -- Lloyd Biggle, Jr. Analog, Apr 1961
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