William H. Magill on 14 Aug 2005 21:12:40 -0000


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Re: [PLUG] Just trying to ping my DSL modem 

On 12 Aug, 2005, at 21:59, Douglas Lentz intoned:

Hi all. Back on 7/21 Luke, David and Christopher were good enough to respond to me re my problems with getting my Verizon DSL connection (my ISP is dca.net) up. Unfortunately, just when they responded to me I had a series of exams at Drexel, and was not able to implement their suggestions then. I have just gotten back to the problem now.

To make a long story short, I have had DSL for a month now, without getting/receiving one byte. But that may not be an extraordinary experience :-)

I have a "static" IP address from DCANET, which means that they promise to keep assigning me the same one via DHCP. (Some confusion surrounds this point. This definition of static IP address is NOT the one the modem's manufacturer has in mind). I believe that DHCP is failing on my RH9 box because I cannot establish connectivity with the ADSL modem, period. So this is not a request to help me get my connection up; at this point, a success condition would be pinging the modem, which I cannot do at this point. OR, another way to say this is that I may need to build a case that the modem is defective, but I would like to establish that scientifically.

Before anything happens, I need to be able to connect to the modem.

The modem is a Zoom 5515 ADSL Bridge. Now according to its docs (which assume Windows user and PPPoe, neither of which is true in my case), if my DSL connection was of the PPPoe variety I should, in ifcfg-eth0, set the IPADDR to 10.0.0.3. Additionally, the modem is supposed to have configuration software at 10.0.0.2.

Please correct me if I am mistaken, I am more of a DBA type than a network person. My idea is: I have a home network. I should be able to pull the ethernet cable running from the RH9 box to the hub OUT of the hub, plug the cable into the modem, and ping the modem at either 10.0.0.3 or 10.0.0.2, and I should get a response even if the modem isn't connected to the phone line. Am I correct? 

No you are not.

The 5515 is a MODEM, not a router! It does not do NAT and does not do DHCP.

It happens to have a Web interface (primarily for firmware updates).
This answers on a different port than a ping.
Very few Modems or Hubs are smart enough to answer a ping.

You can communicate with this Web GUI via your browser and the address 10.0.0.2

The 5515 should work out of the box with no configuration necessary.
It really is just a dumb modem.

The MAC address of your RH9 box needs to be registered with DCAnet to allow it to get the DHCP address from their server. One MAC address = one IP address. Multiple machines need to be registered independently or else you need to run and configure your own Router and or other NAT server.

You say "I cannot establish connectivity with the ADSL modem" -- what does that statement mean? What do the indicator lights show... are you getting "sync" from the DSL line?

The front pannel lights which should be lit: PWR and LINK.
The LINK light will flash during the power-up sequence. Once the modem establishes a "sync" condition with the DSLAM in the CO, this light will go on solid. If it does NOT stay on solid, there is a line problem, most likely the DSLAM needs to be reset. Call DCA, and they can do it while you are on the phone with them.

The LAN light will light up when there is a valid Ethernet connection plugged into the modem. If the light on your Interface card (NIC) does not come on or the light on the Modem does not come on, you do not have a connection in one direction or another. This is true of any two Ethernet connections. You may have a bad cable NIC card or need a "crossover" cable. Note that the 5515 does have a 10/100 interface.


Step 1: ifcfg

The Linux installation instructions are on page 23, Section C. Custom Installation Instructions.

My ifcfg-eth0 file is

DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
USERCTL=no
PEERDNS=no
TYPE=Ethernet
IPADDR=192.168.1.1
NETMASK=255.255.255.0
NETWORK=192.168.1.0
BROADCAST=192.168.1.255
GATEWAY=192.168.1.1


The above config won't work with either DHCP or to contact the modem.

They describe the following settings for ifcfg.

DEVICE=eth0
ONBOOT=yes
BOOTPROTO=static
IPADDR=10.0.0.3
NETMASK=255.255.255.0
NETWORK=10.0.0.2

Run: /sbin/ifdown eth0
     /sbin/ifup eth0

Step 2: Plug the cable from the modem directly into the PC. Try using your browser to reach 10.0.0.2. If that doesn't work, get a "reversed" or "crossover" cable and plug that in (they are usually red). [Otherwise just leave the hub in place. The setup really shouldn't care.]

Step 3:

Reconfigure your interface for DHCP. The two configs are NOT compatible.

Note that you will not be able to contact the modem on the 10.0 address once you get you DHCP interface up unless you get into some serious network configuration games.

If your various lights come on as expected, and the MAC address is correctly registered with DCAnet (typos happen), then the box should simply "come up." There is nothing particularly fancy about your setup. If it does not, the problem is most likely with the DHCP configuration on your RH box.

BTW: The Folks at DCAnet are pretty good with Linux configurations.

I'm not using RH, but FreeBSD and OSX with DCAnet's new "static" DHCP addresses. (I also still have one REAL static IP address, but that's another story.)

T.T.F.N.
William H. Magill
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magill@mcgillsociety.org
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