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Topic: How to configure for Cable Modem DHCP?

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I have two routers: a little WR850g motorola "broadband" router with a web interface that is connected to my cable modem and a linksys WRT54gs running whiterussian .9. My internet provider is comcast.

Since I am configuring my linksys WRT54gs, I  have the WRT54GS plugged into the motorola wr850G.

I can then plug my PC into either the WRT54GS or the WR850G and access the internet.

The WR850g tells me it has a "cable modem (DHCP)" on the wan side.

Apparently, I have my WRT54GS/openWRT set up for DHCP on both sides because my PC is configured as DHCP client.

Why is it that when I plug my WRT54GS/openWRT directly into the cable modem it won't pick up WAN address? I do an ifconfig eth1 and it won't display an address!

However, when I plug it back into theWR850g it will pick up an IP address!

when I do a "nvram show | grep wan" I get (see below).

Is there something special about cable modem DHCP v. normal DHCP?

How do I make my WRT54GS recognize the cable modem DNS?
Thanks,
Siegfried

root@OpenWrt:~# nvram show | grep wan
wan_unit=0
wan_device=eth1
wan_get_dns=
wan_run_mtu=1500
wan_lease=0
http_wanport=8080
wan_gateway=10.169.1.2
wan_domain=
wan_hwname=
wan_netmask=255.255.0.0
block_wan=1
size: 11320 bytes (21448 left)
dr_wan_rx=0
wan_dns=209.97.224.2 209.97.224.3
dhcp_wins=wan
wan_proto=dhcp
wan_hwaddr=00:14:BF:E5:2B:FA
wan_ifnames=eth1
dr_wan_tx=0
wan_primary=1
dhcp_domain=wan
wan_gateway_buf=0.0.0.0
wan_iface=eth1
upnp_wan_proto=
wan_ipaddr=10.169.1.11
wan_wins=0.0.0.0
wan_speed=4
wan_mtu=1500
wan_get_domain=
wan_ifname=eth1
wan_hostname=

Power cycle the cable modem between attempts.  There's always some mechanism to insure 1 IP per customer and this is the most common.

If you want a shot at hot-plugging either device without a power cycle, "clone the MAC" (set WRT54GS wan_hwaddr= to the same as the WR850g WAN MAC or vice versa).

I have no idea how cable modem DHCP is detected... not by official spec, anyway.  Sounds like Motorola does something on their own.

HTH

(Last edited by Bill_MI on 15 May 2008, 12:27)

That reboot did the trick! Thank you! Yahoo!

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