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WNR2000v4 keeps changing internal ip address
Hi there, Since a while I have a strange problem with my WNR2000v4. Every now and again the router changes the internal ip address of itself. The standard/default ip address is 192.168.1.1 but fo...
Hi Andy,
I have some more information on this subject from my ISP community. It is a rough translation with google translate, I hope you understand it.
This seemingly "strange phenomenon" can be explained. What I can say at this stage is that both parties have no guilt here. This phenomenon stems from two requirements that a manufacturer must meet when NAT is used with the product. See https://tools.ietf.org/html/rfc4787#section-4.4 for details.
Why you can see this at a modem reset is because the RF interface of the modem is not connected yet to the CMTS. As a result, the DHCP server of the modem itself is active until there is a connection to the CMTS. The WAN interface of your router detects a link down / up event and then try again to obtain an IP address. The WAN interface from your router will then receive a private IP from the modem of the same sequence which is then used your router at that time. The modem does not know that your router uses internally the same private IP range. This clearly presents a problem and configure your router responds correctly by itself with another private IP range. Why is the DHCP server of the modem active when there is no connection to the CMTS? Because you still can logon to the management interface of the modem.
Manufacturers must implement one of the following two things to make it work.
All traffic between internal / exterene clients correct translation and forwarding. This is difficult because you need a solution such as Session Traversal Utilities for NAT server. If the two clients are the same ISP who does double NAT, you are also dependent on the correct NAT hairpinning implementation of the ISP router.
The second solution is automatically ensure that the internal and external IP ranges do not overlap / are identical.
Manufacturers logically opt for the second easy solution. How can you solve this problem permanently? If your local network eg. 192.168.0.0 Class C network can be used eg. Set your router to use IP network 192.168.1.0.
What is the model number of your Ubee modem please?
If the Netgear router detects an IP address at the WAN port which would conflict with its LAN subnet it will automatically change the LAN subnet to avoid a conflict, and allow the LAN to continue to function. So if the LAN subnet is 192.168.1.x then it would seem that the router has detected the same subnet on the WAN side. This will typically happen where the modem is also a router, very common with DSL ISPs, and sometimes Cable ISPs also.
If you do have a modem/router combo, then it is normally advisable to set the modem to Bridged Mode. If you know the model number of the model run an Internet search on ‘model number Bridged Mode’ and if it is a modem/router then there’s a good chance that the answer to your issue will be there.
Hi Andy, No, it is not a combo. It is just a modem. My ISP does have combo's but I do not want one. I rather have control of things, hehe. Well anyway, sorry for the late answer. I had a RSS feed enabled but it seems not to be working or NetGear is blocking VPN connections. I will check the model number in the morning since it is night time at the moment of writing. I live in the netherlands. Also, subnets are not IP addresses. It is a mask ranging from 255.0.0.0 to 255.255.255.255. And NAT is enabled. Out of curiosity, could this also be caused by a DDOS attack? My ISP had one yesterday on its DNS servers and it seems they having them again today. Also, if I check the logs I see terms like DDOS. Now I come to think of it, I had never this problem but since I check for firmware updates/upgrades I have this problem. I can't be sure though. the version I'm using is 1.0.0.60. Anyway, thanks for looking into this :-)