Can't connect using DHCP

sleepless said:

And the router settings:
Attachment 342347

Out of curiosity, why does the DHCP-assigned IP address range of the router begin at 192.168.0.10? Ordinarily, I would have guessed the default starting IP address to be 192.168.0.2. Did you change this initial default value to 192.168.0.10, or did it come that way from Cisco?

Do you have any other IP addresses between 192.168.0.2 and 192.168.0.9 "reserved" by MAC address?

You've shown the router's "connected devices" summary, with the desktop's now DHCP-assigned 192.168.0.10, as well as the laptop's hard-forced 192.168.0.14. But is there anything in your "pre-assigned DHCP IP addresses"? What is shown if you push that button?

How did you acquire that DPC3825? New? Used? Provided by your cable company or purchased yourself? Does it have the latest version of firmware installed? Doesn't appear to be the world's most universally loved device by user reviewers. A bit of bad-mouthing going on, but that doesn't really have relevance to your specific situation.

Nevertheless, it's honestly quite remarkable that BOTH your wired and wireless connections to the router from the laptop BOTH fail to work with DHCP, but BOTH work with hard-assigned IP addresses. I don't know if that's really a critical problem or maybe just one of life's inexplicable mysteries that we learn to work around and just live with. More specifically, it's hard to conclude that the problem is likely caused on the PC side somewhere in your laptop Windows system, or on the router side (which seems less likely as there's no issue with DHCP performing properly with your desktop machine and its installed Windows system).

One other idea. Seems you can easily try an "address reservation" in the router for both wired and wireless laptop adapters' specific two MAC addresses in the router (say to 192.168.0.2 for wired in the laptop, and 192.168.0.3 for wireless in the laptop), along with "obtain addresses automatically" in the TCPIP IPv4 Properties setup for both adapters on the laptop, to see if that works. You're now kind of bypassing true DHCP in the router by requesting specific 192.168.0.2 and 192.168.0.3 IP addresses to be assigned by the DHCP server mechanism when specific hardware MAC addresses are detected in the connecting device adapters (i.e. in your laptop), but at least your laptop still thinks of it as "obtain addresses automatically" and you haven't set anything hard-assigned in the laptop itself. Your configuration is in the router.

We really don't know where the issue is... whether (a) it's in BOTH of your laptop adapters trying to agree with the router on a true DHCP-assigned IP address, which really seems unlikely, or (b) it's a problem with the router unhappy with BOTH of your laptop adapters in trying to agree on a true DHCP-assigned IP address, which again really seems unlikely. So maybe an acceptable workaround is honestly the best we can hope for. You already have a proven workaround, of hard-specifying the IP address for both wired and wireless adapters in the laptop.

Using "address reservation" by MAC address in the router is truly a standard DHCP technique (coupled with "obtain addresses automatically" in the laptop), for situations such as remotely accessed host/server machines running RealVNC Server which require specific port-forwarding configuration in the router to get through firewalls for remote access from RealVNC Clients. Only when "address reservation by MAC" is used can the specific RealVNC Server machines be consistently accessed via consistent port-forwarding.

So there's nothing improper or non-standard about "address reservation by MAC" simply if you wanted consistent IP address assignment for your particular LAN machines, and I would still think of it as DHCP working properly.

But mostly, I'm curious to know if this particular "reserved by MAC" IP address assignment technique in the router coupled with "obtain addresses automatically" in the laptop, manages to overcome the symptoms we've been fighting, and instead successfully works the same way things do when you hard-assign IP addresses for PC and DNS in the laptop.

sleepless said:

My local ip is 192.168.0.1 but this is what's displayed in ipconfig:

Attachment 342028

thoughts?

I wonder if not having the Default Gateway listed in IPCONFIG is the problem?
Mine:

Out of curiosity, why does the DHCP-assigned IP address range of the router begin at 192.168.0.10? Ordinarily, I would have guessed the default starting IP address to be 192.168.0.2. Did you change this initial default value to 192.168.0.10, or did it come that way from Cisco?

That's the default setting. in this whole process i reset the router to default, just to see if that might solve the problem. it did not.

Do you have any other IP addresses between 192.168.0.2 and 192.168.0.9 "reserved" by MAC address?

No.

You've shown the router's "connected devices" summary, with the desktop's now DHCP-assigned 192.168.0.10, as well as the laptop's hard-forced 192.168.0.14. But is there anything in your "pre-assigned DHCP IP addresses"? What is shown if you push that button?

How did you acquire that DPC3825? New? Used? Provided by your cable company or purchased yourself? Does it have the latest version of firmware installed? Doesn't appear to be the world's most universally loved device by user reviewers. A bit of bad-mouthing going on, but that doesn't really have relevance to your specific situation.

Standard issue from my isp.

One other idea. Seems you can easily try an "address reservation" in the router for both wired and wireless laptop adapters' specific two MAC addresses in the router (say to 192.168.0.2 for wired in the laptop, and 192.168.0.3 for wireless in the laptop), along with "obtain addresses automatically" in the TCPIP IPv4 Properties setup for both adapters on the laptop, to see if that works.

If by "address reservation", you mean pre-assigned addresses, i tried that (not with those specific addresses) - didn't work.

Also, it should be noted that dhcp did work for me in the past. i switched to static ip's years ago and only noticed the problem when i tried to switch back. i have even re-installed windows since then. that is why i'm asking:

ARE THERE ANY WINDOWS PROCESSES/SERVICES THAT ARE REQUIRED FOR DHCP TO WORK?

i realize it's not "really a critical problem", nonetheless i would like to know what's going on.

Berton said:

I wonder if not having the Default Gateway listed in IPCONFIG is the problem?

I'd say it's one of the resulting symptoms, not "the problem" itself.

It's remarkable, that when DHCP is enabled on the laptop the router doesn't see it as a "connected device" via the wired or wireless paths (and thus does not provide either IP for the laptop or IP for the "default gateway" or DNS servers). But when DHCP is disabled on the laptop (and thus DHCP IP address assignment in the router bypassed) the very same still-in-effect wired or wireless connection paths now work fine.

It would seem to be a router issue, but the fact that the second "desktop" machine in the story works perfectly in DHCP mode from the very same router via its wired connection. So that would seem to eliminate the router as the possible culprit, rather than point to it.

I would have suggested trying a different ethernet cable from router to the laptop, but that too is pointless since the same failure occurs on the wireless approach as well.

Again, seems like a problem with the Windows and DHCP in the laptop when communicating to the router for a DHCP-assigned IP and DNS and default gateway address, as the most likely explanation, as it extends across both wired and wireless options to the laptop.

I still want to know the results of the "address reservation by MAC" router configuration with laptop still configured for DHCP with "obtain addresses automatically", to see if that works.

I wonder if not having the Default Gateway listed in IPCONFIG is the problem?

That certainly is a CLUE... i just don't know what it means.

Your "pre-assigned DHCP IP address" screenshot shows the two .14 and .15 static addresses as "reserved". This seems odd to me as these would really be properly shown as "connected devices", not "reserved". I wonder if this is residual from some of your earlier experiments, and the Cisco firmware has not cleared out these entries. I'd like to see if we can purge these two items and see if it makes any difference.

While working from your desktop machine and with your laptop powered off, can you select each one of those individually, and then push the "remove static IP" button to delete the entry. I want you to thus remove both of these entries from that list.

Now power everything off. Shut down your desktop, and pull the power plug on the DPC3825. Let things "rest" for 30 seconds.

Now power the DPC3825 on first, and let all the front panel lights stabilize.

When the DPC3825 is stabilized, power on the desktop. When everything on the desktop machine is stabilized, connect to the router and re-verify that only the desktop machine (what you called "HTPC" I believe?) shows up in connected devices as well as "active" in the pre-assigned list (although I find that kind of odd, since you didn't actually pre-assign it yourself I don't believe, per your story). Or is it not shown in the pre-assigned list? Anyway, hopefully the previously present .14 and .15 entries should definitely NOT be shown.

Now, finally, and with DHCP enabled on the laptop (i.e. "obtain addresses automatically" checked), power on the laptop and let it stabilize (to whatever it gets). Now once again, get back into the router from your desktop machine, and see what shows for both (a) connected devices, and also (b) pre-assigned address. What shows?

sleepless said:

If by "address reservation", you mean pre-assigned addresses, i tried that (not with those specific addresses) - didn't work.

Yes, by "address reservation" I did mean manually creating entries in that "pre-assigned IP address" list to correspond to both your wired MAC (say, addressing it with 192.168.0.2) and wireless MAC (addressing it with 192.168.0.3) in your laptop.

Now when your laptop is booted and tries to connect to the router through DHCP instead of with a hard-requested IP address for laptop and DNS servers, either/both of the laptop's MAC addresses would be recognized by the router in this list you just placed those MAC addresses in, and the specified 192.168.0.2 and/or 192.168.0.3 addresses should then be assigned. This is conceptually just as "DHCP-assigned" as anything 192.168.0.10 or higher, except that you've requested the router's DHCP mechanism to assign a specific IP address instead of taking one from the available pool above 192.168.0.10.

I'm just interested to see what this results in... same failure as before, or does it actually work.

Your "pre-assigned DHCP IP address" screenshot shows the two .14 and .15 static addresses as "reserved". This seems odd to me as these would really be properly shown as "connected devices", not "reserved". I wonder if this is residual from some of your earlier experiments, and the Cisco firmware has not cleared out these entries. I'd like to see if we can purge these two items and see if it makes any difference.

I tried that already AND reset the router completely to default - no dice. those reserved settings are there so that the router doesn't assign the static ip addresses to another device. the desktop (HTPC) doesn't need a reserved/preassigned address because it has been assigned by the router(dhcp) and the router knows not to assign the same address to another device.

i will try again, using the power on/off instructions you suggested. in the adapters tcp/ipv4 properties should i have the "obtain dns server address automatically" checked, or should i fill in my routers dns settings?

sleepless said:

I tried that already AND reset the router completely to default - no dice. those reserved settings are there so that the router doesn't assign the static ip addresses to another device.

But they didn't just get there by themselves. They either became part of that list automatically placed there (by the router) when you manually configured your laptop's two adapters with these addresses to get things to work, or you manually "pre-assigned" them yourself into that router list at some time in the past.

However they got to be in that list I'd like to at least ensure that they are NOT present when you next boot your laptop and try to get DHCP-assigned IP and DNS addresses assigned by the router, same as happens naturally and properly for your desktop machine.

the desktop (HTPC) doesn't need a reserved/preassigned address because it has been assigned by the router(dhcp) and the router knows not to assign the same address to another device.

Well that's what the "connected devices" list information conveys. So why does an entry appear in TWO lists for this router? Again, may be right for this equipment, but it does seem odd.

If an IP address is dynamically assigned by DHCP, I wouldn't expect it to appear in the "pre-assigned" list. That's only for manually reserved IP addresses for specific devices identified by their MAC address.

Here's my own Netgear router's (a) attached devices, and (b) pre-assigned address reservations [in two shots]. Note that I currently do not have any dynamically assigned IP address devices present (i.e. with IP addresses 192.168.1.20 or higher, which is the starting point for DHCP in my configuration).

NOTE: every single device in my home LAN which has an "address reservation" entry for it, is itself configured for "obtain IP address automatically" (i.e. from its perspective, assigned through DHCP) with the router itself recognizing the particular MAC addresses in its "address reservation" list and assigning the requested specific IP addresses accordingly. But the devices themselves, in each PC or player, TV, etc., thinks it is getting a "dynamic DHCP-assigned address".










And I need the "address reservation" to assign fixed IP addresses to certain of the PC's on my LAN because I use RealVNC to communicate with my home machines from my laptop when I'm out of town. This makes use of port-forwarding on the router, but to do that reliably you need to have static IP addresses in order to port-forward consistently.