We have, for quite some time, had problems with systems on our LAN coming up “bottled,” i.e., with non-functional connections. I recently noticed that the assigned IP addresses looked like they were colliding with fixed IP addresses on the LAN, which suggested that either the router/firewall (a TP-Link TL-WDR4300) wasn’t honoring its DHCP range, or there was a rogue DHCP server in the network.
This morning, my iMac came up “bottled,” and I was able to determine that the IP address had been vended by a DHCP server at the cable modem’s address (192.168.0.1), even though the setup page for the cable modem shows DHCP as unchecked. Then, later, when I brought up my Chromebook (which almost always initially comes up “bottled”), I looked more closely at the address it had been assigned: it wasn’t a collision with a fixed address (e.g., 192.168.1.102) at all; rather it was an address in the cable modem’s range: 192.168.0.103.
This raises three questions:
- Why is the cable modem’s DHCP server running when it’s supposedly disabled?
- Why are addresses in the 192.168.0.x range “bad” on our network?
- What can I do about it?
Answer
rather it was an address in the cable modem’s range: 192.168.0.103.
I found that my router came up in ‘bridged’ mode, and then acquired an IP address and configured the NAT. When the whole network came up after a power outage, the clients and the router were doing DHCP renewal at the same time the router was in bridge mode, and the DHCP traffic was leaking through to the ISP, and back to … well, in my case my DHCP server was seeing it, and going offline because it didn’t think there should be two conflicting DHCP servers on the same network segment.
Attribution
Source : Link , Question Author : hbquikcomjamesl , Answer Author : user165568
