[techtalk] MAC addr from Cable Modem

Kelly Lynn Martin kelly at poverty.bloomington.in.us
Wed Jan 19 03:01:30 EST 2000

On Tue, 18 Jan 2000 21:05:39 -0800 (PST), moebius at ip-solutions.net said:

>  I don't know if that  is normally the case, however I would think that
>it would not be. The reason that I say this is that the cable modem is not
>directly connected to the computer. It is connected thru cat5 cable.
>ifconfig reports (I may be wrong here) on system devices only. Arp should
>report on it, I'm not sure what's up with that. On my network arp only
>reports 3 out of 4 computers MAC addr. The fourth doesn't even show up,
>even though it's live. Any other suggestion?? This dang thing has got me

Oh, so the cablemodem is connected to a hub, along with several other
devices?  If that's the case, I would think you'd have to use some
sort of tool (usually provided by the cable modem manufacturer) to
configure the cable modem.  

Arp is a passive system: it just reports on the IP addresses it sees
attached to Ethernet hardware addresses.  You might trying seeing if
the cablemodem is trying to RARP its IP address by compiling RARP
support into your kernel and running rarpd.  Then if you get a RARP
packet from an ethernet hardware address you don't recognize, you
could set up rarpd to give that ethernet address the IP you want the
cablemodem to have.  This won't help you with routing, though, and
probably is of no real help at all. :)


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