[wellylug] saturn cable connection with linux
Mark
mark at incet.com
Mon Feb 4 23:29:26 NZDT 2002
sorry to mislead the rfc I quoted should be rfc 1918 :)) not 1912 which
is more related to
well know music !!
Mark wrote:
>Hi Don,
>
>This is a little bit of info I am aware of about Hybrid Fibre Coax Networks:
>
>Downspeed bandwidth is greater than upspeed about 30MB:10MB I believe
>
>your bandwidth for your modem is rateshaped according to your contract
>
>Network is partitioned and there is an effective broadcast network
>within the segment
>
>the total bandwidth on the segment is shared between the users on that
>segment
>
>there is filtering so that if you sniff traffic on the modem you see
>only your traffic and broadcast traffic (like a switch)
>
>the network acts a layer 2 bridge with filtering, the modem has no ip
>address for the customer traffic
>you cannot use a hub directly into the back of the modem since you only
>get 1 real ip
>
>If you try to use a hub and use private IPs on the hub then those
>machines will not be able to use the internet because the source ip of
>the packets are in the RFC1912 address space and will be dropped by the
>internet
>
>if you wish to use > 1 PC on the network configure 1 with Linux and then
>have 2 network cards and plug the hub into the second card as already
>described previously and then your setup will work for multiple PCS.
>
>you canot bypass the modem - the cable is broadband (data modulated on a
>number of carrier frequencies) and ethernet is baseband where the data
>signals are written to the media without any modulation. The cable
>modem does the modulation/demodulation. An analogy would be connecting
>your pc serial port to the phoneline!!
>
>any help
>
>mark
>
>
>
>
>Don Jones wrote:
>
>>Hmmm
>>
>>Im getting a saturn cable modem installed on Friday
>>
>>>You plug your ethernet card into the cable modem
>>>
>>using the ethernet
>>
>>>cable they provide.
>>>
>>Is this a X-over do you know?
>>
>>>Saturn give you an IP address, a netmask, a
>>>
>>gateway address and two dns
>>
>>>servers.
>>>
>>Whats the netmask?
>>
>>The description suggests that the saturn cable
>>"modem" is just a bridge/media converter/layer2
>>device. Has anyone investigated this? Essentially
>>the whole cable network is one big LAN. This
>>suggests that anyone who plugs the "modem" strait
>>into a hub with a number of hosts on it is
>>essentialy an extension of the lan. Except with a
>>bridge in between. So presumably it filters
>>incomming frames at the "modem" based on its
>>external MAC address. That will allow filtering of
>>inbound frames (ie you wont be able to sniff traffic
>>on the main LAN beyond the bridge). But what about
>>frames comming from internal hosts in the hubbed
>>setup described above, how does the bridge decide
>>which frames to forward? Either it forwards then all
>>and you have internal addresses out on the main
>>segment or does it do some kind of arp or deny any
>>ip addresses in the internal range? - whatever -
>>either would bump it up to a layer 3 device - anyone
>>know??
>>
>>I wonder what the specs of the segment are - is it
>>real ethernet (anyone know what type?) - 100Mbps or
>>Gigabit (its probably 1544Mbps or something)? Could
>>you hack together a connector to bypass the modem -
>>like a bnc 10base2 card running at whatever the
>>segments speed is? or some type of coax to cat5
>>media convertor running at the right speeds.
>>
>>Forgive my ramblings - but Im curious ;)
>>
>>Don Jones
>>
>
>
>
>
> .-. Wellington
> /V\ Linux
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