IP Passthrough instead of bridge mode in VDSL wireless router?

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Level 1

88 points

IP Passthrough instead of bridge mode in VDSL wireless router?

From my ISP, Swisscom, I have a Netopia VDSL modem *** wireless router. When I had ADSL, I just configured the router for bridged mode, connected it to my AirPort Extreme Base Station's WAN port, and configured the AEBS with the information it needed to login to the service. The AEBS did NAT and DHCP for the network. Now, that no longer works. The VDSL modems use some other means of identification, then they receive an IP address. So now I have to let the VDSL modem do NAT and DHCP, and have to put the AEBS in bridged mode. The problem is, some features of OS X 10.6, e.g., Wake on Demand (incl. wireless connections) don't work if the AEBS is in bridged mode.

Therefore, I was wondering whether the IP Passthrough feature of the VDSL modem/router is an alternative. As I understand the feature, the VDSL modem/router can be configured to pass its "outside" IP address to a device on the network. In my case, that would be the AEBS. The AEBS would then do NAT and DHCP for the devices connected to it. The only problem I see is, it seems that the VDSL modem/router must have DHCP service available so as to assign its outside address to the AEBS, so there would be two DHCP servers that would could respond to a DHCP client connecting to the AEBS.

Does anybody have any experience with this?

MacBook Core 2 Duo 2 GHz, MacBook Pro i7 2.66 GHz 17" glossy screen, Mac OS X (10.6.4), 8GB RAM

Posted on Jul 6, 2010 3:39 PM

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Answer 1

adsfushi72

Level 4

1,115 points

Jul 7, 2010 11:49 AM in response to Richard Liu

I'm pretty sure your router isn't assigning the Extreme your outside address but rather forwarding it all inbound traffic.
In any case, it wouldn't make sense for IP Passthrough to make the router act as a DHCP server, since the purpose of IP Passthrough is to let another device on the network handle all routing functions.

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Answer 2

Richard Liu Author

Level 1

88 points

Jul 7, 2010 7:31 PM in response to adsfushi72

No, from what I can gather from a manual describing how to configure IP Passthrough on Netopia modem/routers, the public IP address is being being shared. The manual distinguishes two cases: (a) if the modem/router has a fixed address, the other device must be configured to connect to it with that address; (b) if the modem/router receives its IP address, it must be configured to assign it to a device with a particular MAC address using DHCP. This does not mean that the LAN portion of the modem/router performs DHCP, but that it is using DHCP (or something like it) to get its WAN addres, and the other device will use DHCP to maintain the correct WAN address, Gateway, DNS, etc. So I think I can use IP Passthrough as a substitute for running the modem/router in bridged mode. The manual warns, however, that once IP Passthrough is enabled, the modem/router can no longer be managed remotely over the WAN address. That, as I understand it, is the reason my ISP doesn't want users to run the modem in bridged mode,

Will try this when I have enough time to make and rectify mistakes.

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