Orbi WiFi 7 RBE973
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RBR750 DHCP

costler
Tutor

RBR750 DHCP

I have an Orbi RBR760 connected to my cable modem, also Netgear.

My network Gateway / DHCP is 10.0.0.x.  Works as advertised, most of the time.  However, I noticed a number of connected devices that have 192.168.2.x for IP addresses.

192.168.2.x is not configured on any device in my network.  The MAC address goes to my Orbi router.

 

Suggestions on how I resolve this?  Firmware is current, says the website.

Message 1 of 14
FURRYe38
Guru

Re: RBR750 DHCP

What Firmware version is currently loaded? v.2 is most current for the 7 series:

https://community.netgear.com/t5/Orbi-WiFi-6-AX-and-WiFi-6E-AXE/New-RBR750-RBS750-Firmware-Version-4...


What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too?

 

What mode is the RBR working in? Router or AP mode? 

 

There a screen capture of what your seeing that you can post here? 

Message 2 of 14
plemans
Guru

Re: RBR750 DHCP

What actual netgear modem is it? 
Usually if the router switches off the default ip address, the modem its connected to isn't just a modem, its a modem/router combo device. 

Its why model numbers help. 

If it is indeed a modem/router combo device, it causes a double nat. 

A double nat happens when you cascade more than 1 router.
https://kb.netgear.com/30186/What-is-Double-NAT
Fixes? There’s 3 options but only use 1.
1. Put the modem/gateway in modem only/pass through mode. This disables its routing functions.
2. Leave the modem/gateway in router mode but put the Netgears IP address into its DMZ. This forwards the data to the netgear. You can either leave the modem/gateway’s wireless enabled or disabled. Just make sure its using a different wifi channel to prevent interference. Probably not the option I'd use.
3. Put the Netgear router into access point mode. This disables its routing functions. Wifi/ethernet still works but it does disable some features.
https://kb.netgear.com/26765/Which-features-are-disabled-on-my-NETGEAR-router-when-it-is-set-to-AP-M...

 

I'd probably go with option 1 or 3. 

Message 3 of 14
CrimpOn
Guru

Re: RBR750 DHCP


@costler wrote:

My network Gateway / DHCP is 10.0.0.x.  Works as advertised, most of the time.  However, I noticed a number of connected devices that have 192.168.2.x for IP addresses.

192.168.2.x is not configured on any device in my network.  The MAC address goes to my Orbi router.


The default LAN IP subnet for Orbi routers is 192.168.1.x.  When the router is connected, it requests an IP address for the WAN port.  If this IP address is in the 192.168.1.x subnet, then the Orbi changes to 10.0.0.x for its LAN subnet.  (That is the other private IP space.)  This can be verified by checking the IP address that shows on the Orbi web interface, Advanced Home Page in the box labelled "Internet Port".

 

There are two ways a device gets an IP address:

  • A manual setting on the device itself (usually called a static IP).
  • Using DHCP, where the device broadcasts a request and accepts the first DHCP server to respond.  Usually, there is only one DHCP server in the local broadcast subnet (the router).  Things can get really ugly when there is another DHCP server in the network.

Could you please report the "internet IP" of the router?

Is it possible to access any of the devices with that 192.168.2.x IP address to see what they report as their Gateway IP?

Message 4 of 14
costler
Tutor

Re: RBR750 DHCP

Thanks for the replies

The Modem is a Nighthawk AX6 (CAX30).  WIFI disabled (in all of the many places it shows up).  I have tried to turn off the router mode, the Orbi end of things then stopped working.  I had to factory reset the Nighthawk to get back online.  It does have a 170.x.x.x ip address from my ISP.  DHCP for the LAN is 192.168.1.x the scope allows for only two IP addresses. firmware v1.4.10.8

 

RBR750 is in Router mode.  Firmware v4.6.5.14, one satellite.  Used to have two, one refuses to do anything, so I unplugged / deleted it.  DHCP scope is 10.0.0.2 - 10.0.0.77

When I look at attached devices there are 6 that have 192.168.2.x for an IP address, and to add to the mystery, they all work / internet / all good. They show a gateway of 192.168.1.1 ARP -a presents me with the Orbi MAC address.

 

What I do not have is the DHCP scope of 192.168.2.x configured on any device on the network.  Even if I was, it shouldn't work. I used to be a Banyan / Cisco network engineer, so this bother me.

 

While my Bandwidth and connectivity with the Orbi has been great, I find them extra special flakey.. I had a firmware problem last winter and Supports only answer was to do a hard reset.  If I can't run this down, I may have to put the Orbi stuff on craigs list and go purchase something better.

 

Message 5 of 14
CrimpOn
Guru

Re: RBR750 DHCP

Wow. What a puzzle!

 

To recap:

  • The CAX30 WAN port has a public IP address.
  • The CAX30 LAN port has 192.168.1.1
  • Nothing is connected directly to the CAX30 besides the RBR750.
  • The RBR750 WAN port has IP 192.168.1.2
  • The RBR750 LAN port is IP 10.0.0.1
  • The RBR750 DHCP range is 10.0.0.2 - 10.0.0.77
  • The router Attached Devices page shows devices with both 10.0.0.x and 192.168.2.x IP addresses.
  • When you dump the entire ARP table on a PC, there are entries with both 10.0.0.x and 192.168.2.x IP addresses.

Can you share the type of devices that have 192.168.2.x IP addresses?

Is the Guest WiFi network enabled?

Message 6 of 14
FURRYe38
Guru

Re: RBR750 DHCP

Modem mode on the CAX would be recommended. If you set this, the modem should reboot and if you power OFF the RBR while it's in router mode, it should get a clean WAN IP address from the modem. Thus by passing all the double nat issues that you seem to be having. 

 

I recommend trying the CAX modem in modem mode and the RBR in router mode. 

https://kb.netgear.com/27191/How-to-set-the-cable-modem-router-to-be-on-modem-only


@costler wrote:

Thanks for the replies

The Modem is a Nighthawk AX6 (CAX30).  WIFI disabled (in all of the many places it shows up).  I have tried to turn off the router mode, the Orbi end of things then stopped working.  I had to factory reset the Nighthawk to get back online.  It does have a 170.x.x.x ip address from my ISP.  DHCP for the LAN is 192.168.1.x the scope allows for only two IP addresses. firmware v1.4.10.8

 

RBR750 is in Router mode.  Firmware v4.6.5.14, one satellite.  Used to have two, one refuses to do anything, so I unplugged / deleted it.  DHCP scope is 10.0.0.2 - 10.0.0.77

When I look at attached devices there are 6 that have 192.168.2.x for an IP address, and to add to the mystery, they all work / internet / all good. They show a gateway of 192.168.1.1 ARP -a presents me with the Orbi MAC address.

 

What I do not have is the DHCP scope of 192.168.2.x configured on any device on the network.  Even if I was, it shouldn't work. I used to be a Banyan / Cisco network engineer, so this bother me.

 

While my Bandwidth and connectivity with the Orbi has been great, I find them extra special flakey.. I had a firmware problem last winter and Supports only answer was to do a hard reset.  If I can't run this down, I may have to put the Orbi stuff on craigs list and go purchase something better.

 


 

Message 7 of 14
CrimpOn
Guru

Re: RBR750 DHCP


@FURRYe38 wrote:

Modem mode on the CAX would be recommended. If you set this, the modem should reboot and if you power OFF the RBR while it's in router mode, it should get a clean WAN IP address from the modem. Thus by passing all the double nat issues that you seem to be having.

A bit annoying that this is not mentioned in the CAX30 User Manual.  Have no idea what this would do to the LAN Setup Table for any devices which have assigned IP addresses.


 


 

Message 8 of 14
FURRYe38
Guru

Re: RBR750 DHCP

Ya not sure why it's not in the manual. Should be. Need good information on features that the modem does support. Modem mode is one of them. I presume maybe NG wants users to use the CAX in gateway mode rather than modem mode. Just make things easier to make the CAX into modem mode. 

I've done this myself with mine and works well. 

 

I have static assigned IP addresses however there always on the main network (192.168.0.1) for me. I have setup a 2nd router behind the primary and always use 192.168.1.1 for those and avoid mixing devices between them. Limited devices on the 2nd router whilst testing. 

 

My ISP is gracious though to allow me to have more than 1 WAN IP address on my CAX so while in modem mode, I can have two or more routers connected and all have different WAN IPs. 😉


@CrimpOn wrote:

@FURRYe38 wrote:

Modem mode on the CAX would be recommended. If you set this, the modem should reboot and if you power OFF the RBR while it's in router mode, it should get a clean WAN IP address from the modem. Thus by passing all the double nat issues that you seem to be having.

A bit annoying that this is not mentioned in the CAX30 User Manual.  Have no idea what this would do to the LAN Setup Table for any devices which have assigned IP addresses.


 


 


 

Message 9 of 14
costler
Tutor

Re: RBR750 DHCP

I think you nailed it.

 

While I just looked at the list of attached devices.  What type of devices?  My phone, one laptop, iPad, other assorted smart switches.  they are ALL on the Guest network.

 

So I did a search for orbi rbr 750 Guest network IP range.  Appears that the guest network is responsible for the 192.168.2.x ip range.  Explains why the MAC address is the RBR 750, I should have noticed that.  I was hyper focused on how that IP range would even work, it would appear Netgear does it in the background. But this makes me question what the heck else is it doing all on it's own?

 

No double NAT issues.  Tracert PC-> Obri -> Cable Modem -> ISP - > destination

 

Thanks

Message 10 of 14
FURRYe38
Guru

Re: RBR750 DHCP

GN defaults to 192.168.2.1

If you have the Orbi in AP mode then there wouldn't be a double NAT issue. 


If you have the Orbi in router mode along with the CAX, this will be a double NAT issue. 

 

 

Message 11 of 14
CrimpOn
Guru

Re: RBR750 DHCP


@costler wrote:

Appears that the guest network is responsible for the 192.168.2.x ip range.  Explains why the MAC address is the RBR 750, I should have noticed that.  I was hyper focused on how that IP range would even work, it would appear Netgear does it in the background.


This is one of the design changes Netgear made between the original Orbi and the AX series.

  • The original Orbi had both primary and guest WiFi in the same IP subnet. This forced Netgear do track which devices were in the guest network in order to prevent them from accessing the primary network. (The original Orbi provided an option to allow devices on the guest network to interact with the primary network, or to prevent it.)
  • On the AX series, Netgear put guest devices in a separate subnet, which made preventing interaction trivial.

I've always wondered what caused Netgear to pick 10.0.0.x for the Orbi LAN subnet when the WAN port was in 192.168.1.x

There were hundreds of 192.168.?? subnets to choose from.

One would think that when the primary subnet changed to 10.0.0.x, then the guest subnet also should have changed.  But... oh, well.

 

On the topic of Double NAT.  There are specific applications which a Double NAT will affect (port forwarding, some internet gaming, UPnP, etc.) Internet search will turn up examples, such as https://kb.netgear.com/30186/What-is-Double-NAT   There are (literally) hundreds of thousands of customers who exist blissfully ignorant that they have a Double NAT.  All those people who just take their new WiFi system out of the box, connect the Ethernet cable, and proceed to use it. (Google, Asus, Linksys, Netgear, eero... all brands and models).

As long as they do not run into one of those specific applications, they never know. As a test, I connected three routers in a row:

ISP modem ->to->router 1->to->router 2->to->router 3-> PC.  Everything I tried on the PC worked fine: email, web browsing, video streaming, YouTube,  It was a challenge, but I was even able to forward a port through all three routers to a server on the PC.

Message 12 of 14
SeaRefractor
Apprentice

Re: RBR750 DHCP

I noticed that there had not been a mention of the service you are using to connect to the internet.

There might be a fourth option.   

I had double-NAT issues and while I could put the modem/router into bridge mode, I still wasn't pleased with the performance.

I have Fiber to the home (CenturyLink).   So I had an Adtran ONT -> Zyxel C3000Z -> Orbit RBR750.

I found out the settings I needed from CenturyLink support (my PPPoE username/password and the VLAN tagging I required) and configured those on my Orbi RBR750 and returned the Zyxel C3000Z to CenturyLink.   No need to lease the modem any more.

 

I don't know if this at all applies to your setup, but I wanted to post that there could be a fourth option (if ethernet handoff is provided from an ONT device that is not the Modem/router) if a similar setup.

Message 13 of 14
FURRYe38
Guru

Re: RBR750 DHCP

In this case they have a CAX30. Similar to the CAX80 I have. Can run double NAT and should work. However when encountering odd LAN IP addressing problems and such, sometimes it makes things easier to put the CAX to modem only mode and then run the RBR in router mode. KISS. 😘

Message 14 of 14
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