[LARTC] arp-proxy and advanced routing problem

[LARTC] arp-proxy and advanced routing problem

[Arne Hueggenberg]

Hi,

i have a problem with my setup.
The box has 3 interfaces
to the cable modem,
to the dsl modem
to the switch serving our other boxes

all boxes on the switch have static ips
behind the cable modem is a subnet with hosts with static ips on the sae 
subnet
in behind the cable modem is also the default 

the arp-proxying is done between the cable interface and the switch interface

the third goes to the adsl modem
we do masqing on this interface

now, some of the boxes on the switch are supposed to go out over the adsl 
line, and some are supposed to go via the gateway behind the cable modem.
default route via the adsl, and a seperate table for those supposed to go via 
the cable.

Now, when we add that table everything works as its supposed to.
But if a windows box reboots it suddenly complains the switch interface had 
its ip and doesent configure the interface
if we remove the table it boots fine

Anyone have an idea what might be the problem?

-- 
Arne 'zal' Hueggenberg <zalaster@nef.wh.uni-dortmund.de>


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Re: [LARTC] arp-proxy and advanced routing problem

[Julian Anastasov]

	Hello,

On Tue, 11 Dec 2001, Arne Hueggenberg wrote:

> Hi,
>
> i have a problem with my setup.
> The box has 3 interfaces
> to the cable modem,
> to the dsl modem
> to the switch serving our other boxes
>
> all boxes on the switch have static ips
> behind the cable modem is a subnet with hosts with static ips on the sae
> subnet
> in behind the cable modem is also the default
>
> the arp-proxying is done between the cable interface and the switch interface
>
> the third goes to the adsl modem
> we do masqing on this interface
>
> now, some of the boxes on the switch are supposed to go out over the adsl
> line, and some are supposed to go via the gateway behind the cable modem.
> default route via the adsl, and a seperate table for those supposed to go via
> the cable.
>
> Now, when we add that table everything works as its supposed to.
> But if a windows box reboots it suddenly complains the switch interface had
> its ip and doesent configure the interface
> if we remove the table it boots fine
>
> Anyone have an idea what might be the problem?

	It seems the proxy ARP feature is activated for wrong route.
See the following URL and try to differentiate your devices by the
medium they are attached to. Then your router will know that the
target host can see the broadcast probes and will not reply for them.
For this to work, you need correct routes. The problem can be that
the proxy_arp feature does not know that two devices are attached
to same medium and the ARP reply should not be generated.

http://www.linuxvirtualserver.org/~julian/#medium_id

As I can't fully understand your settings, if you have some questions,
please provide some settings. And of course, the main thing: how
many distinct mediums you have. Read medium_id.txt for more
information.

Regards

--
Julian Anastasov <ja@ssi.bg>


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Re: [LARTC] arp-proxy and advanced routing problem

[Arne Hueggenberg]

On Wednesday 12 December 2001 00:38, you wrote:
> Hello,
>
> On Tue, 11 Dec 2001, Arne Hueggenberg wrote:
> > Hi,
> >
> > i have a problem with my setup.
> > The box has 3 interfaces
> > to the cable modem,
> > to the dsl modem
> > to the switch serving our other boxes
> >
> > all boxes on the switch have static ips
> > behind the cable modem is a subnet with hosts with static ips on the sae
> > subnet
> > in behind the cable modem is also the default
> >
> > the arp-proxying is done between the cable interface and the switch
> > interface
> >
> > the third goes to the adsl modem
> > we do masqing on this interface
> >
> > now, some of the boxes on the switch are supposed to go out over the adsl
> > line, and some are supposed to go via the gateway behind the cable modem.
> > default route via the adsl, and a seperate table for those supposed to go
> > via the cable.
> >
> > Now, when we add that table everything works as its supposed to.
> > But if a windows box reboots it suddenly complains the switch interface
> > had its ip and doesent configure the interface
> > if we remove the table it boots fine
> >
> > Anyone have an idea what might be the problem?
>
> 	It seems the proxy ARP feature is activated for wrong route.
> See the following URL and try to differentiate your devices by the
> medium they are attached to. Then your router will know that the
> target host can see the broadcast probes and will not reply for them.
> For this to work, you need correct routes. The problem can be that
> the proxy_arp feature does not know that two devices are attached
> to same medium and the ARP reply should not be generated.
>
> http://www.linuxvirtualserver.org/~julian/#medium_id
>
> As I can't fully understand your settings, if you have some questions,
> please provide some settings. And of course, the main thing: how
> many distinct mediums you have. Read medium_id.txt for more
> information.






{public subnet with gateway} -- --[cable modem]
                                                                         |
                                                                         |
 [box 1 with ip on public subnet]                |
                                          \                        /   |
                                           \         proxy-arp  |
                                           \                 /          |
                                            [switch]-- - - - -linux router}
                                          /                             |
                                       /                                |
 [box 2 with ip on public subnet]                |
                                                                         |
                                                                         |
                                                                 [adsl-modem]
                                                                         |
                                                                         |
                                                                         |
                                                                        ISP


So the linux router has 3 ethernet cards
proxy arp is needed between the switch and the cable modem
reason being that the cable modems use Time Division Multiplexing, and with 
everyone her using his own cable modem performance goes against 0
unfortunalty the cable modems only work with a single mac adress on the other 
end, so we have to do proxy arp

now, box 1 is supposed to be routed via the gateway behind the dsl line, and 
box 2 is supposed to be routed via the gateway on the subnet behind the cable 
modem.

Wich works fine if i add the necessary rules, except for the fact that if box 
1 wich runs windows is rebooted it complains about the linux router stealing 
its ip adress

so the linux router has host routes for box1 and box2, a network route for 
the public subnet and a default route over the DSL, with an table for box 
specifying the gateway behind the cable modem as default route

only that when the tables up we run into problems with the proxy-arp

cant access the box right now so i cant post configuration yet, but will as 
soon as its back up

> Regards
>
>--
>Julian Anastasov <ja@ssi.bg>

-- 
Arne 'zal' Hueggenberg <zalaster@nef.wh.uni-dortmund.de>


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