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Re: VOIP with a linksys PAP2

On 6/13/05, Kevin J. Cummings <cummings kjchome homeip net> wrote:

eth1 is neither UP, nor has any IP address information  (no IPADDR, no
NETMASK, no BROADCAST) so TCP/IP will not work over it.  Furthermore,
regardless of what may be attached to the network it is plugged into,
none of your routing referes to it (probably a side effect of not being
configured!  B^)

what's meant by "configured"?  I ask because I've used eth1 to connect
to the internet.  after physically installing eth1 and rebooting I was
presented with a menu and selected, IIRC, DHCP.

"Configured" is the actual assignment of the necessary configuration information necessary to make the device function in the desired environment. (obscur enough for you? B^) In this case it would refer to the assignment of an IP address, a Netmask, and a Broadcast mask, and the appropriate changes made to the kernel routing table in order to accommodate the network interface into your working network. *HOW* these attributes come to be assigned to the network interface may be because you selected DHCP, or because you entered them directly into a network configuration program. Ultimately, it doesn't matter which, the end result is that they must be assigned. In what you showed us with the output of the "ifconfig eth1" command, your eth1 interface is *NOT* configured at the time you ran the command. It *must* ultimately be configured in order for it to work. Period.

Furthermore, you need to keep your network interfaces straight. In your original email, you mentioned that your internet interface was through eth0. Above you say you've used eth1 to connect to the internet. You can't start waffling the device names when you start presenting actual command output if you want to get the correct advice from the people helping you out! Please!

thank you all so much for the help here :)

If you have no devices on the eth1 network which will be DHCP servers, you'll either have to run one on your Linux computer for it, or you'll have to configure the TCP/IP staticly (ie, pick a private subnet network address for it, and configure the network interface at boot time, and configure all devices on that network so that they all have different address in the same subnet. Basic TCP/IP administration, this is what we used to do before there was a DHCP standard!)

I'm pretty sure that if you run system-config-network (as root) you'll
see that the eth1 interface is *NOT* active.  However, don't despair,
its the right tool to configure that interface for you!

right, and "menu-->system tools-->network device control" also seems to bring this up. isn't DHCP preferable because it's less fragile?

I don't understand "If you have no devices on the eth1 network which
will be DHCP servers..." when on the eth1 network will be a hub and
the VOIP PAP2.  is the PAP2 or the hub a DHCP server?  I'd think not,
but don't know.

Read your owner's manual and be sure. If it isn't, it probably is expecting to exist in an environment where a DHCP server is available to it. If that is the case, you'll have to run one on your Linux computer which will serve addresses out to clients on the eth1 network so that they can work, and your Linux computer can forward their TCP stuff off to your internet service when necessary. That means at least turning on IP forwarding in your Linux kernel, and possibly doing either NAT on your computer, or turning it from a router into some kind of a bridge so that the eth1 devices can communicate on the internet [my personal opinion is that a seperate routed network is easier to configure and administer, but, I could be wrong, and often am!]

From my experience, I originally set my own Linux computer up as the firewall/router/NAT for my home network which includes 4 M$-Windows machines for the wife and kids. The Cable modem is connected to one of my ethernet cards, the home network was connected to the second, and my machine performed IP forwarding and NATing for the internal network. I know how it works, and I've been doing it for almost 10 years now (OK, I started with a SL/IP dial-up line before I got the cable modem). Just a couple of months ago I inserted a Linksys 802.11g router after the cable modem, and added my computer to the internal network. That means the Linksys router is now doing DHCP for the house network instead of my Linux computer. The end result is that the *rest* of the computers on my home network didn't really see any difference in their network configuration! The Linksys does everything for them that my computer used to do. (OK, I'm still the SAMBA master, but that's another story).


You're very welcome! Good Luck!

Kevin J. Cummings
kjchome rcn com
cummings kjchome homeip net
cummings kjc386 framingham ma us

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