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The simplest and cheapest method of accessing the 5100b/4100/4100b modem GUI through a router is explained in the section "Let the modem do the PPP and issue a public/private IP to wan/internet port of router" at the bottom of the page here: »AT&T Midwest/Ameritech FAQ »Funhouse 5100b Setup and Reference Info and for the Motorola 2210 modem the explanation is here: »AT&T Midwest/Ameritech FAQ »Modem GUI access with a router ; however, sometimes there can be disadvantages to allowing the modem to make the PPPoE connection such as problems with some on-line games or P2P traffic.

An alternate method of accessing the modem's GUI when a router makes the PPPoE connection can be set up by inserting an inexpensive five-port switch (or hub) between the modem and the router. This works because the PPPoE-encapsulated traffic "tunnels" directly from the router through the switch to the modem without problems, but any other non-PPPoE-encapsulated traffic on the the 192.168.0.x subnet will be directed by the switch to the modem's GUI. Note: That this arrangement with appropriate IP adjustments can also be used for modem models other than the 5100b/4100/4100b or 2210.

So what other type of ethernet connections can be made to the switch to access the modem?:

Method 1: A computer off the LAN and dedicated to the collection of modem stats could be set up.

Method 2: A computer on the LAN, but with a second NIC set to the 192.168.0.x subnet could be connected to the switch.

Method 3: A second router in parallel with the primary router that bridges the 192.168.0.1 traffic.

This secondary router can be an old unused unit or it could be a wireless router that also adds wireless connectivity to the LAN. Both routers are assigned IPs on a subnet that isn't 192.168.0.x or 192.168.1.x. The DHCP function on the second router must be disabled. A patch cable connects a LAN port on the primary router with a LAN port on the secondary router.

In the following diagram, the primary router is set to make the PPPoE connection. The secondary router should be set to "Obtain an IP automatically" if the modem is in "PPP on the computer" mode or set to the static IP of 192.168.1.64 as stated at the bottom of this FAQ: »AT&T Midwest/Ameritech FAQ »Funhouse 5100b Setup and Reference Info if the modem is in the "Bridged Mode".

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From the command prompt, you must then run the following command for each LAN computer that is to access the modem GUI:

route -p add 192.168.0.1 mask 255.255.255.255 A.B.C.Y metric 5

The "-p" option make this routing persistent even after a computer reboot. The A.B.C.Y IP is the secondary router's IP. This command line could also be placed in a BAT file to be run as necessary.

The command: route delete 192.168.0.1 will erase the routing from the computer permanently if needed.

The background for this portion of the FAQ was derived from the discussions in this thread: »Viewing Modem Stats? Thanks to Bill_MI See Profile for the router set up details.

Method 4a: A connection from the router's switch to the five-port switch without the secondary bridging router.

The router is set to make the PPPoE connection. A patch cable connects a LAN port on the router with a port on the five-port switch. The computer's NIC is set to a wider mask than the typical 255.255.255.0 mask. The diagram shows it set to 255.255.0.0, but this could be restricted to 255.255.252.0 if there is some need to do so such as to allow connections through a VPN to other 192.168.x.x subnets.

Note: This method should only be used with static IPs on the LAN or with the modem's DHCP server disabled. The modem's DHCP server can be disabled by bridging or by accessing the CLI: »SBC DSL FAQ »How can I use the cfg command on the Speedstream modem?. Unintended routing results occur if the router is set up as a DHCP server and the modem's DHCP server is still active. For example, a DHCP client device on the LAN can end up with the 192.168.1.64 address issued by the modem's DHCP server instead of the intended address.

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Although this method requires less equipment than the other methods, it does produce slightly more traffic activity on the LAN. All the LEDs on all the equipment that show ethernet activity will blink simultaneously and the router logs might show false "intrusion" attempts on the WAN from the computer and modem broadcast traffic.

On occasion certain LAN devices can lose the path through the switches to the gateway router, 192.168.2.1, and packets will end up attempting to pass into the WAN port of the router. A router logging program could record this as an "attack" by your LAN device on your router. If this happens, either temporarily unplug the patch cable connecting the router port with the 5-port switch or disable the port through the router's GUI (if this option is available), then reboot the problem device and/or 5-port switch as necessary to restore the proper path to the router's switch side.

The method was modified from the discussions in this thread: »switching to dslextreme - question on setup. Thanks to sded See Profile for the ideas.

Method 4b: A connection through the router's switch without requiring the separate five-port switch of Method 4a.

Follow the directions and note given for Method 4a. The one drawback of this method, of course, is that it uses more wired ports, but if a wireless router is used, this may not be such a problem. The packet path stability of this method is unknown and it may require some manual attention on router reboots.

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The method was suggested by S_D See Profile.

Method 5: A connection from a dual WAN router to a five-port switch that uses the second WAN of the router for modem access. This can also be done with certain firmwares on WRT routers that will make the router's switch port act as a second WAN. The second WAN is then set to be a static IP: 192.168.0.100, Mask: 255.255.255.0, Gateway: Router's IP, DNS: Router's IP.

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Feedback received on this FAQ entry:
  • I have an Asus RT-N16 with TomatoUSB and a Billion 7800N. I've been able to allow access to the modem just by adding a second IP to the WAN interface My RT-N16 has LAN IP 10.0.0.1 /16, and my 7800N has LAN IP 10.1.1.1 /24 I added these to a startup script: ifconfig vlan2:0 10.1.1.2 netmask 255.255.255.0 iptables -t nat -I POSTROUTING -o vlan2 -j MASQUERADE You just need to make sure you use an IP in the same subnet as your modem's LAN, and different to your router's LAN. Also make sure the vlan number is correct for your WAN (my router uses vlan2. These commands create a new alias of vlan2 called vlan2:0)

    2013-04-24 12:06:48

  • With DD-WRT, you can do this without any additional hardware by enabling proxy ARP: /usr/sbin/ip addr add 192.168.0.2/24 dev eth1 brd + /usr/sbin/ip route del 192.168.0.0/24 dev eth1 /usr/sbin/ip route add 192.168.0.1 dev eth1 /bin/sh -c "/bin/echo 1 > /proc/sys/net/ipv4/conf/eth1/proxy_arp" /bin/sh -c "/bin/echo 1 > /proc/sys/net/ipv4/conf/br0/proxy_arp" The above commands are for a Buffalo G300NH using eth1 as the WAN interface. For a Linksys WRT-54GL, replace eth1 with vlan1. Your mileage may vary.

    2012-10-11 12:45:33 (bk1e See Profile)

  • THANK YOU THANK YOU THANK YOU. Option 4b is by far the coolest trick I have seen in years, which should be flattering, since I have worked in the industry for years. Thanks again.

    2010-07-24 10:28:44



Expand got feedback?

by d_l See Profile
last modified: 2010-08-07 18:15:22