Anyone have a Vizio router? (DHCP problem)

[Ichinisan]

If you have a Vizio router, could you change the DHCP starting address from 192.168.1.100 to 192.168.1.101 and tell me if the setting does anything? You might have to reboot the router and your devices.

Back story:

I talked to a customer today and she has a Vizio-brand router. These are usually sold in the home-theater section of department stores, intended for use with network-capable TVs and BD players. It's dual-band and allows different SSIDs and security settings for the 2.4Ghz and 5Ghz networks.

I'm not sure how a Vizio-brand router got installed in an office environment. They say there's no network-capable TV or player. It's the only Vizio-brand device they have. Long story (relatively) short, the customer is convinced that someone is hacking their network because she keeps getting a LAN IP address conflict with 192.168.1.100

The wireless security on both networks was using WPA2 with a very secure passphrase, so I told them that an intrusion is unlikely. Still, I changed the SSIDs slightly in case a neighbor in-range has similar settings:

"VIZIO HD" --> "VIZIO HD 5Ghz"
"VIZIO" --> "VIZIO 2.4Ghz"​

We also changed the WPA passphrases again. We checked the configuration of every computer to determine if one had manually-entered the 192.168.1.100 address, but they were all configured for DHCP. There is no network printer and, supposedly, no other network devices. Anyway, we do know which two devices were conflicting: 1) A wireless laptop computer and 2) A wired desktop computer.

We set the DHCP starting IP to 192.168.1.101 and saved settings. Rebooted the router and the computer. Manually did ipconfig /release and ipconfig /renew ...The desktop computer now has 192.168.1.101, but the laptop keeps pulling 192.168.1.100

Either the router is ignoring its own setting for "DHCP starting address," or the laptop is somehow hanging-on to the 192.168.1.100 address and causing the conflict. I'm guessing the latter is most-likely.

Has anyone ever seen this before?

 

[imagoon]

DHCP will keep using the assigned address as long as the lease hasn't expired even if the DHCP server is off line. Likely the laptop is not getting a NAK for the address and will keep using it unless you release it.

 

[Ichinisan]

DHCP will keep using the assigned address as long as the lease hasn't expired even if the DHCP server is off line. Likely the laptop is not getting a NAK for the address and will keep using it unless you release it.

Thought of that.

... Manually did ipconfig /release and ipconfig /renew ...

Thanks, though. Any other ideas?

 

[imagoon]

If a device is not releasing a DHCP lease it normally means it thinks it is ok. I would trace the line myself but if this is a customer site that might not be easy. DHCP is all broadcast so the requests will show up on an wireshark scan.

You can also try to release and renew while the router is off. If it gets 192.168.1.100 again that means there is more than one DHCP server on the line.

 

[Ichinisan]

If a device is not releasing a DHCP lease it normally means it thinks it is ok. I would trace the line myself but if this is a customer site that might not be easy. DHCP is all broadcast so the requests will show up on an wireshark scan.

You can also try to release and renew while the router is off. If it gets 192.168.1.100 again that means there is more than one DHCP server on the line.

I haven't been physically on-site, but I did some remote assistance through http://join.me/

You might be correct about another DHCP server.

 

[imagoon]

Seems common enough to me. Someone got a new wifi router and the old one is still the acting as the NAT device or something.

Wireless LAN adapter Wireless Network Connection:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Dell Wireless 1510 Wireless-N WLAN Mini-C
ard
   Physical Address. . . . . . . . . : C0-CB-38-7B-93-F5
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   Link-local IPv6 Address . . . . . : fe80::f1f5:3298:2905:7b84%11(Preferred)
   IPv4 Address. . . . . . . . . . . : 192.168.1.119(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Lease Obtained. . . . . . . . . . : Tuesday, March 20, 2012 8:09:33 AM
   Lease Expires . . . . . . . . . . : Saturday, March 24, 2012 4:00:41 AM
   Default Gateway . . . . . . . . . : 192.168.1.1
   DHCP Server . . . . . . . . . . . : 192.168.1.1
   DHCPv6 IAID . . . . . . . . . . . : 226026496
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-13-65-45-B2-B8-AC-6F-62-A4-2C

   DNS Servers . . . . . . . . . . . : 8.8.8.8
                                       8.8.4.4
   NetBIOS over Tcpip. . . . . . . . : Enabled

The "DHCP Server" ip should match the router that gave it the lease.

 

[Ichinisan]

Seems common enough to me. Someone got a new wifi router and the old one is still the acting as the NAT device or something. Didn't check to see if the DHCP server was a different IP, but if the assigned IP was 192.168.1.100, then I'm guessing the DHCP server has the same IP as the Vizio router (assuming there *is* a rogue DHCP server).

Wireless LAN adapter Wireless Network Connection:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Dell Wireless 1510 Wireless-N WLAN Mini-C
ard
   Physical Address. . . . . . . . . : C0-CB-38-7B-93-F5
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   Link-local IPv6 Address . . . . . : fe80::f1f5:3298:2905:7b84%11(Preferred)
   IPv4 Address. . . . . . . . . . . : 192.168.1.119(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Lease Obtained. . . . . . . . . . : Tuesday, March 20, 2012 8:09:33 AM
   Lease Expires . . . . . . . . . . : Saturday, March 24, 2012 4:00:41 AM
   Default Gateway . . . . . . . . . : 192.168.1.1
   DHCP Server . . . . . . . . . . . : 192.168.1.1
   DHCPv6 IAID . . . . . . . . . . . : 226026496
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-13-65-45-B2-B8-AC-6F-62-A4-2C

   DNS Servers . . . . . . . . . . . : 8.8.8.8
                                       8.8.4.4
   NetBIOS over Tcpip. . . . . . . . : Enabled

The "DHCP Server" ip should match the router that gave it the lease.

I did ipconfig /all, but only looked at the gateway IP (192.168.1.1), which took me to the Vizio router interface (no authentication required). From the ISP end, the Vizio's WAN MAC is seen and it has a valid public IP.