New Contributor
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11 Messages
Router not honoring blocked devices, nor reserved IP addresses
Hi there, we just had a router failure and comcast replaced our Cisco router with a Technicolor CGA4332COM. Having some weirdness now.
Our printer has needs a static (local) IP address. So I reserved the proper IP with the printer's MAC address. Seemed to work OK. Then I got a call today- printer isn't printing. Asked the person onsite to browse to the printer's management IP address- no luck.
Upon investigation, I found another device had been issued the IP address that is reserved for the printer. How does that happen?
In order to remedy the issue, I blocked the device that was issued the "Reserved" IP address. It still showed online, so I rebooted the router. That enabled the printer to pick up its proper reserved IP address. However, the printer does NOT show up in the list of connected devices- it shows up in the "offline devices" pane in the display.
Then I noticed the device I had blocked was ONLINE after the reboot- it was issued a different IP address. I double checked- the MAC address is in the blocked list, "Always" block. And even in the "connected devices" list, the "X" on the far right- where you click to block a device- wasn't there!! So the router knows it is blocked, but allows it on the network anyway. Why??
The device with the reserved IP is hardwired ethernet via an external switch if that makes a difference. The "blocked" device is on WiFi via our Cisco mesh system which is also ethernet hardwired to the router (via an external switch)- it only does wifi, no DHCP or anything like that.
So I have three problems in one issue here.
#1- Why does the router issue an IP address that I have set up as "reserved"?
#2- Why does that device with the reserved IP not show up in the connected devices list as being connected? (Yes, it's connected, I can ping, print, browse the management interface, arp -a shows the mac address of the printer, etc.)
#3- Why is a device that has its MAC in the "Blocked Devices" list allowed on the network?
Thanks.
Comcast_ThomasD
Official Employee
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22 Messages
4 months ago
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buckyswider
New Contributor
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11 Messages
4 months ago
Hi Thomas, thanks for the reply, but did you read my question fully? Or maybe you're a bot? I have set a reserved IP address for a device, and the router's DHCP client gave that IP address to a DIFFERENT client.
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buckyswider
New Contributor
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11 Messages
4 months ago
I may have some partial answers- but I'm not sure.
It is possible that the reserved IP address was issued before the address reservation was added to the configuration shortly after the gateway was replaced. But the gateway was rebooted many times after that- why didn't the gateway force the client to re-register after the reboot? DHCP has a function FORCERENEW- which should be implemented any time the router notices an improper client which has a reserved IP that doesn't belong to it. Possible yes, but after the gateway was replaced I browsed to the management interface of the printer to make sure it was working properly, and it worked then. So I don't think that's the case, but it may be.
#2- Although DHCP gave the blocked client an IP address, I found a "reports" tab under "Content Filtering". Running the report showed the MAC of the blocked client and a large number under "Attempts" - like 400, with "Device Blocked" listed. I would think that blocking a device wouldn't even allow it on the network (i.e. deny the DHCP request) but it looks like it's just blocking all traffic. Oh well.
Still no idea why the device with the reserved IP isn't showing up as a connected device. And an arp -a says that the IP is dynamic. Weird.
(edited)
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