[nzlug] Telstra/linux

[Mathew Carley]

As I was trying to explain, I *think* that these modems are simply 
bridges, and if the firmware on mine is anything to go by, it doesn't 
have the ability to configure the IP address in the modem web-interface. 
I would think that if the modem is going to be set by anything, it would 
be by TFTP based on your node id on the cable network, and then your NIC 
just uses the cable modem as the interface to the network, rather than 
itself, as it seems that the MAC addresses stored within the cable modem 
are somehow important (MAC based routing of some sort?)

My eth0 settings are (as per ifconfig in Linux or ipconfig in Windows):
IP Address: 82.181.11.134
Subnet: 255.255.248.0
Default Gateway: 82.181.8.1

Which suggests that 1. Modem is a bridge, not a router and 2. your IP 
address on eth0 should *not* be an internal one, but set to whatever 
Telstra tells you to... I'm able to get my IP address by DHCP based on 
my MAC address or something, so I don't have to worry about it. My Mac 
is different again with 62.something... this causes some difficulties 
when trying to do any file sharing between the two computers, but its 
not often that I have to.

Don't ask me how I am still able to access my modem via 192.168.100.1 
when my ethernet cards IP address is not on that range... everything 
from networking 101 says that it doesn't make sense and I shouldn't be 
able to get to that address, yet I can. Maybe its a weird routing thing 
on their part which I never really noticed. My tracerts on the first hop 
are always to 10.202.64.1 which just makes things more confusing and/or 
fun :)

[OT] By the way, its good to see that Telstra is upping speeds and 
monthly limits. It would still only be about 5 days usage for me on 
their 80G plan but its a big improvement over a couple of years ago 
(even if the price more than double what I pay here for unlimited 
traffic). Are the DSL plans getting any better yet?

Mathew

Phillip Hutchings wrote:
> On 7/4/07, Volker Kuhlmann <hidden at paradise.net.nz> wrote:
>> > The modem IP address is http://192.168.100.1/
>>
>> Yes. The point to remember is that you may need a static route forcing
>> packets addressed to 192.168.100.1 out the interface to which the modem
>> is connected, if your local network setup wouldn't do this otherwise. Eg
>> you will need this route if you have a firewall (which you ought to have
>> with telstra cable!!) and you want to browse the modem from the inside
>> computers.
>
> If the default gateway is through the modem it will just work. The
> only time it would be a problem is of your internal network is
> 192.168.100.0/24 or you filter out RFC1918 addresses that aren't in
> your network at the firewall level.
>