Weird shared secret issues

Ivan Kalik tnt at
Sun May 4 19:16:35 CEST 2008

If you have a spare box on a local network, switch that supports VLANs
and a router that can tag VLANs - you can spoof the whole outside
network with simple IP/VLAN configuration:

configure a gateway IP interface for the network you want to spoof on
your router and tag it with testing VLAN ID - that will create a locally
connected routing table entry - no creative manual entries needed

configure testing VLAN ID on the switchport to which you will connect the
testing box

configure IP you want to spoof on the testing box

That shouldn't take more than 5 minutes. Just make sure that you remove
the spoofed gateway interface from the router after testing in order to
be able to use the real network.

Ivan Kalik
Kalik Informatika ISP

Dana 4/5/2008, "Tuc at T-B-O-H.NET" <ml at> piše:

>> Hi,
>> > 	Tech calls in and say that he can't get an appliance working in the field.
>> > I ask him what secret he's using and the IP address of the appliance. I want to
>> > be able to be locally logged onto the radius server and use radtest/radclient/rad????
>> > to be able to query radius asking "If I was IP, and I gave you SECRET, would you
>> > authorize me?".
>> >
>> > 	So I want to be on, but say I'm on . Right now, If I
>> > say I'm on, it still wants the secret for .
>> you want to spoof the source address? tricky.  one 'easy' way to do this would
>> be to create a local VPN/GRE tunnel on the linux box under which you could
>> emulate a remote link.
>> configure freeradius to also listen on that virtual address, run the
>> radclient with the destination being the end point of the VPN - the
>> linux routing tables would then come into play.  you'd have to
>> reconfigure the VPN end addresses etc each time to emulate an
>> outside world link...but it would work.
>	Not worth it. All I'm looking to do is get programatic confirmation
>that the ip/secret combination in the field is correct. Since this is an
>appliance, not an OS, I don't have access to radtest on the appliance. To
>have someone start setting up VPN/GRE/etc is more hassle than its worth.
>I just have to tell the tech to RTFD closer. I was just hoping I could
>put together a local form on a webserver that could shell out to a script
>to make the test.
>	We'll just have to suffer. :) (Or ask the manufacturer to include
>a utility in the "diagnostic" section)
>		Thanks, Tuc
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