[SOLVED] Router Rejecting Static IPs

[FishEye18]

Okay, this is a really weird problem I dealt with yesterday and found a workaround for, but still left me with a weird question: can a standard home router deliberately block static IP's?

The setup I had:
Router: 192.168.0.1/24
Workstation: 192.168.0.2/24 (Static)
File Server VM (bridged): 192.168.0.3/24 (Static)
Laptop Ethernet: 192.168.0.4/24 (Static)
Laptop Wireless: DHCP
DHCP Range is from .10/24 to .100/24

The night before the issue popped up network connectivity to the Workstation dropped. I was going to bed and figured the ISP was brainfarting as it does every so often. Next morning the Workstation and file server had no connectivity at all. Other dhcp devices like my laptop where fine.

Long story short, after verifying configurations, checking the ethernet cables with my cable tester (our pet likes to chew on things), and multiple restarts of all computers and the router, the only thing that I could prove was the router was blocking devices with static IP's both inside and outside of the dhcp range. At the time I did not reserve DHCP addresses for my three systems. The Laptop could access the router and internet on wireless, but had zero connection using ethernet unless I put the ethernet port on DHCP.

LAN connectivity with static IP's, with the router disconnected from the ISP, was completely FUBAR unless I put the devices on DHCP. If I used the workstation's Wireless with the static address and the ethernet disabled the wireless would disconnect, this was repeatable with the Laptop. I even shut down the laptop to isolate just the router and Workstation and the same thing occurred. If using ethernet with wireless disabled I could often only get one ping to the router and then no more at all. I attempted to verify the possible presence of an overlap both with ping and the router admin page, there was no other devices on except for the the Workstation & Laptop.

The final workaround in which all devices have confirmed connectivity is currently:

Router: 192.168.0.1/24
Workstation: 192.168.0.2/24 (Reserved DHCP)
File Server VM (bridged): 192.168.0.3/24 (Reserved DHCP)
Laptop Ethernet: 192.168.0.4/24 (Reserved DHCP)
Laptop Wireless: DHCP
DHCP Range is from .2/24 to .100/24


And now for the ultimate question, What? Can a home router just randomly decide to block devices that don't use DHCP? Is this a poorly thought out security or idiot proofing update, like websites that block me from pasting in passwords from my password manager? Am I now a Russian hacker because I use static IP's and AMD CPU's? Did I not burn enough of the sacred incense for the Router's machine spirit?

I'm just really really confused as to why Reserved DHCP works but static doesn't, despite the first set up listed as having worked just fine for almost a year with no changes. Nothing on my networking courses or CCNA covered this kind of issue with routers demanding DHCP be used. (And no, I could not find a new security setting for that either.)

 

[kanewolf]

Okay, this is a really weird problem I dealt with yesterday and found a workaround for, but still left me with a weird question: can a standard home router deliberately block static IP's?

The setup I had:
Router: 192.168.0.1/24
Workstation: 192.168.0.2/24 (Static)
File Server VM (bridged): 192.168.0.3/24 (Static)
Laptop Ethernet: 192.168.0.4/24 (Static)
Laptop Wireless: DHCP
DHCP Range is from .10/24 to .100/24

The night before the issue popped up network connectivity to the Workstation dropped. I was going to bed and figured the ISP was brainfarting as it does every so often. Next morning the Workstation and file server had no connectivity at all. Other dhcp devices like my laptop where fine.

Long story short, after verifying configurations, checking the ethernet cables with my cable tester (our pet likes to chew on things), and multiple restarts of all computers and the router, the only thing that I could prove was the router was blocking devices with static IP's both inside and outside of the dhcp range. At the time I did not reserve DHCP addresses for my three systems. The Laptop could access the router and internet on wireless, but had zero connection using ethernet unless I put the ethernet port on DHCP.

LAN connectivity with static IP's, with the router disconnected from the ISP, was completely FUBAR unless I put the devices on DHCP. If I used the workstation's Wireless with the static address and the ethernet disabled the wireless would disconnect, this was repeatable with the Laptop. I even shut down the laptop to isolate just the router and Workstation and the same thing occurred. If using ethernet with wireless disabled I could often only get one ping to the router and then no more at all. I attempted to verify the possible presence of an overlap both with ping and the router admin page, there was no other devices on except for the the Workstation & Laptop.

The final workaround in which all devices have confirmed connectivity is currently:

Router: 192.168.0.1/24
Workstation: 192.168.0.2/24 (Reserved DHCP)
File Server VM (bridged): 192.168.0.3/24 (Reserved DHCP)
Laptop Ethernet: 192.168.0.4/24 (Reserved DHCP)
Laptop Wireless: DHCP
DHCP Range is from .2/24 to .100/24


And now for the ultimate question, What? Can a home router just randomly decide to block devices that don't use DHCP? Is this a poorly thought out security or idiot proofing update, like websites that block me from pasting in passwords from my password manager? Am I now a Russian hacker because I use static IP's and AMD CPU's? Did I not burn enough of the sacred incense for the Router's machine spirit?

I'm just really really confused as to why Reserved DHCP works but static doesn't, despite the first set up listed as having worked just fine for almost a year with no changes. Nothing on my networking courses or CCNA covered this kind of issue with routers demanding DHCP be used. (And no, I could not find a new security setting for that either.)

It could be a security feature. The equivalent of MAC filtering. If MAC not in the DHCP table the drop packets.

 

[bill001g]

That would be strange since network should be able to run 100% static.
What you could try to do is ping between the 2 devices that have static IP on ethernet. The lan ports in most routers are the same as a unmanged switch. It does not have the feature to filter traffic at a layer 2 level. Now this is your more standard consumer routers if you have something different then it could have some kind of special feature that does that.

 

[FishEye18]

It could be a security feature. The equivalent of MAC filtering. If MAC not in the DHCP table the drop packets.

That actually makes the most sense. There is MAC filtering options on the router, but none I saw related to DHCP, but the behavior was similar. With just my laptop, workstation, and a switch, they pinged each other just fine. Add in the router and it rejected all of them no matter which port on the switch I used. However, the lack of configuration option for such a thing if it is indeed the actual case is very, very annoying.