AT&T U-verse → Re: BGH 210 IP Passthru Help

Hello, Economist:

Thank you for your detailed and informative explanation; I really appreciate it. Please, allow me to ask for a few clarifications, around the two (2) DHCP Servers on the BGW210.Regarding the above quote, is the DHCP Server that you are talking about here, is this the DHCP Server indicated in the IP Passthrough section, defaulted at ten (10) minutes? I am asking because I am under the impression that this ("IP Passthrough DHCP Server") is a separate DHCP Server from what I am calling the "main" DHCP Server of the BGW210, which, in following your great explanation, continues to hand out DHCP addresses to other devices connected to the BGW210, not singled out, in the IP Passthrough section of the BGW210, based on the specified MAC address within the IP Passthrough section. Are these actually two (2) different DHCP Servers on the BGW210? Or, is the "IP Passthrough DHCP Server" setting merely a subset or feature of the "main" (and only) DHCP Server of the BGW210 and the interface is simply listing it as a DHCP "Server?"

I guess my question is coming from the fact that you can select a different lease time for the "IP Passthrough DHCP Server," for forwarding the "copy" of the public IP address, to one's 3rd-party router and this lease time is separate from the "main" DHCP Server" lease setting of the BGW210, which is handing out private IPs to any other device connected to the other LAN ports of the BGW210. I apologize for my wordiness; I'm trying to fully understand the interface interrelationship of the BGW210's two (2) DHCP lease settings.

Again, I really do appreciate you taking the time to clarify this for me, Economist; thank you.

There is only 1 DHCP server in the BGW, but it has a separate lease time setting for IP Passthrough vs everything else connected to it. IP Passthrough provides the public address IP number to the Netgear via DHCP.

So, I guess you could consider that a 2nd DHCP server, but there is no address pool, only the 1 public address copy to hand out to the single device you selected from the IP passthrough device list. I think of it as a single DHCP server with its regular address pool + the 1 public IP that is bound to the device on the IP passthrough device list. This is just like any other router. You can bind 192.168.1.5 to your Amazon Fire TV by binding 192.168.1.5 for the FireTV MAC address. Whenever the router received a request from that MAC address, the DHCP server gives that MAC address 192.168.1.5. With IP passthrough, whenever the MAC address of the Netgear requests an IP, the DHCP server hands that MAC address the public IP address as its leased IP. MAC addresses are how the DHCP server recognizes which device is which. It doesn't know *Netgear* obviously, only the unique number 00-14-22-01-23-45 that might be its MAC address.

The lease time on the IP passthrough is probably short just in case the gateway when it renews its own lease with AT&T, gets an public IP change. That public change needs to be quickly passed off to the Netgear, but won't unless the Netgear asks for it which it won't do unless the lease is up. If your public IP was 99.99.10.12, that IP is passed to the Netgear. But if the IP changes to 99.99.22.41, Netgear will wait until its lease of 99.99.10.12 expires. Set that time to 10 minutes and you have the wrong address for only 10 minutes before it says, hey, renew my lease and BGW give Netgear the new IP.

What gets confusing sometimes is that the BGW is both a DHCP server and a DHCP client. IT is a client to AT&Ts DHCP server, but the gateway is a DHCP server for the LAN clients connected to it. The netgear is the same way. It is a client on the WAN side, but DHCP server on the LAN side.

Clients do not get to chose their lease time. That is done by a DHCP server. The client option is to manually release and then renew the IP, which basically gives back the IP to the IP address pool and then asks for the DHCP server to issue another IP.

So AT&T DHCP has a lease time, say 12 hours. Every 12 hours the BGW renews the lease with AT&T or you can do it sooner manually by rebooting the BGW or doing a release renew of its public IP.

Then the BGW DHCP has its lease time for its clients, like your TV STBs, or any devices connected to it. Its defaults is 24 hours. Your TV boxes and any other devices like PCs renew their IP leases every 24 hours.

Then you have the Netgear. It has its own DHCP server with its own lease times. Again, clients will renew their leases per the interval specified in the Netgear DHCP settings.

BUT, Netgear does not set the time between getting its IP from the BGW. The BGW does not set the time between getting its IP refreshed from AT&T. DHCP servers set the lease times, not the clients.

I use pass through on my 210 and set the lease time to 1 day so it matches my Asus router. No issues doing this. I also disable all settings on the 210 firewall and allow the Asus router to handle the v4 and v6 firewall duties. I have nothing hooked to the 210 except the router.

Hello, Economist:

Once again, I could not have asked for a better explanation; thank you! What was a little fuzzy after reading AT&T's IP Passthrough documentation is much clearer, now. Jim721, thank you, too, for your explanation of your setup. This is how I am envisioning setting up a network for a new client. Specifically, I was wondering if setting the BGW210's IP Passthrough separate DHCP lease time setting to match that of the client's 3rd-party router DHCP lease time setting (1 day) might cause some issues and figured the client might have to wait about a day or so, to see any potential conflicts. I had considered testing all devices with much shorter DHCP lease time settings, but, time got away from me. It's good to see that you, Jim721, are not seeing any issues in configuring your setup this way, too, if I am correct in assuming that when you say your BGW210's DHCP lease time setting of one (1) day is referring to your "IP Passthrough" DHCP lease time setting, verses your BGW210's "main" DHCP server lease time setting, which, of course, I assume could also be set to one (1) day. Finally, my understanding is that everything will be fine, so long as one's 3rd-party router's DHCP lease time setting is equal to or longer than the BGW210's IP Passthrough DHCP lease time setting. In the end, my initial confusion came from AT&T's forum post (»forums.att.com/t5/AT-T-I ··· 4#M29310), specifically, where AT&T says this, regarding the IP Passthrough DHCP lease time setting:

"DHCP Lease: By default, the IP Passthrough host's DHCP leases will be shortened to two minutes. This allows for timely updates of the host's IP address, which will be a private IP address before the WAN connection is established. After the WAN connection is established and has an address, the IP Passthrough host can renew its DHCP address binding to acquire the WAN IP address. You may alter this setting."

As you can see, AT&T lists (what I assumed to be) the default IP Passthrough DHCP lease time setting as two (2) minutes, not ten (10) minutes. While at the same time, they have an image indicating this same IP Passthrough DHCP lease time setting as ten (10) minutes and a second image with this setting (presumably) changed to one (1) day. Finally, they also have an image of text listing this default IP Passthrough DHCP lease time setting as two (2) minutes. Therefore, my assumptions began with the impression that the text listing two (2) minutes and the image of text listing two (2) minutes as the default IP Passthrough DHCP lease time setting came from an earlier firmware version of the BGW210 and/or from another AT&T gateway, altogether.

Hopefully, my attempt to help clarify this for myself and others is not making this worse, especially after Economist's explanations have been so helpful, detailed, and appreciated.

Disabling the DHCP also disables the Passthrough. For some reason, the BGW DHCP setting is for both Private and Public. I kept it on, but narrowed my Private DHCP pool to 1 Private IP & then IP Allocated it to my Gateway as fixed. This fixed the issue WTH the 1 day renewal dumping access to my BGW & forcing me to Factory Reset.

Since the gateway and personal router are on different subnets, I did not bother restricting either.

Do I disable all the firewall settings on the BGW210? Some settings are already off.

If I turn off flood limit, all the flood limit boxes below it stay on and cannot be changed.

Flood Limit

Flood rate limit
e.g. 4
Flood burst limit
e.g. 8
Flood limit ICMP enable
Flood limit UDP enable
Flood limit TCP enable
Flood limit TCP SYN-cookie

All firewall settings are disabled. The first Flood Limit function controls the following six sub Flood Limit functions. Those six functions are disabled when the main function is set to off.

Thanks. I see this for my firewall status. is this correct?

Firewall Status
Packet Filter On
IP Passthrough On
NAT Default Server Off
Firewall Advanced nil

Also when I click on Ip allocation I see this. Earlier today it showed my ASUS router,

IP Allocation
There are no DHCP clients and no IP Allocated clients

Obviously I have done something wrong. suggestions on what to do?

Appreciate the help.

Packet filter should be disabled.

Follow the guide in the link below. It references the NVG589 but the settings are the same for the BGW210.

»AT&T U-Verse FAQ »How do I setup bridge mode in the Motorola NVG589?

Thanks. Followed the guide but still no DHCP clients and no IP Allocated clients. I guess this doesn't matter since everything appears to be working.

If the Broadband IPv4 Address on the BGW210, and the WAN IP address of your router are the same, you have successfully implemented IP Passthrough.

They match. Thanks for the help!

Thanks for the link. I've been running a passthrough on my DSL RGW for ages and just got fiber hooked up this morning. Since it's something that doesn't get messed with once it's running, that step-by-step really helped.

The only real change is that firmware v1.5.12 forces DHCPS-fixed instead of -dynamic (which I had been using). No biggie.

Fixed, dynamic and manual are the three options available.

I know what the options are. Just for kicks, select DHCPS-dynamic. Then try to point it to your router.

Have fun.

I misread your post the first time. I read it as fixed was the only option.

If your using your own router why would you need dynamic anyway ? Fixed is the right way to set up your own device.

If you had read my first post you would see that I said 'No biggie'. It's two ways to do the same thing and I used to do it the other way. Now I do it this way. It does not matter and I said as much.

Hi, you seem to be very knowledgeable with setting hardware up. I am having a hard time getting the Netgear XR500 and BGW210 setup properly in passthrough. I get 940/940 through the BGW210 wired to start with. I followed a couple random guides but to help get it setup but nothing was tailored to this specific router. I had it running for a little bit and then all of a sudden it kept losing connectivity repeatedly and rebooting the BGW210 and XR500 did nothing to help it.

Can you help with a simple step by step guide?

Try this guide. It works for the 210.

»AT&T U-Verse FAQ »How do I setup bridge mode in the Motorola NVG589?

Hi
I just came to this post
Could you please tell me what should I use for the lease time?
I have the BGW210-700 and the asus ac5300, I get disconnected every 15 or 20 minutes and it reconnectes by itself, could the lease time be the issue?
I currently have the default 10 minutes.
Thank you in advance for your help
Mario