HardwareBanter - View Single Post - Mysterious internet/ethernet issue (kinda need testing/connection/communicationservice to diagnose it ???)

**Char Jackson** · October 12th 18, 09:16 PM posted to alt.comp.hardware.pc-homebuilt

On Fri, 12 Oct 2018 11:31:53 -0700 (PDT), wrote:

Annoying perhaps, but critical to the success of any networking, whether
local on your LAN or extending to the Internet as a whole. Simply put,
the netmask tells you which part of an IP address refers to the network
and which part identifies the particular host.

I know this already, it's very vague, cause all kinds of network types possible.

Also how to calculate this netmask in the head ?

Just use an IP calculator. There are tons available on the web.

Very hard to do requires calculating some bitmask and then converting that to decimals... ok I can do that.

Why not enter all this stuff in bits in the first place, maybe be a bit easier and prevent this conversion calculation.

Then the thing that gets even worse is this /24 specifier...

The /24 is shorthand for 255.255.255.0. Both formats show that 24 bits
are being used to specify the network and the other 8 bits are being
used to identify the hosts on that network.

What is this supposed to mean ?

Also can netmasks be 10101010101 or always 1111111 ?

The first case is my guess, which makes very little sense.

Play with an IP calculator to see what happens when you adjust the
netmask. Bottom line, when sending IP traffic from a networking device
such as a PC, the netmask is consulted to see whether the destination is
local or remote. If it's local, use ARP to find the physical address
(MAC address) of the device that owns the destination IP. If it's
remote, slap the physical (MAC) address of the gateway onto the packet.
Every device on the local network will see the packet, but all devices
will ignore it except for the device that has a matching MAC address,
the gateway in this example. The gateway will strip off its own MAC from
the packet and replace it with the MAC of the next device upstream, then
forward it on to that device. At each hop, the destination IP stays the
same but the destination MAC changes, until it finally reaches its
destination. That will be where the destination IP and the destination
MAC refer to the same networking device.

Perhaps these guys trying to access their ziggo modems are talking about two different things:

1. The status page of the modem.
2. The menus of the modem.

They are trying to access 1, which is cut off from them, only from external it can be seen.

Not sure if these guys can access 2.

What would cause 2 to not be available ?

If I set my cable modem to bridge mode or some other crazy setting is there a chance the webserver won't work anymore ?

What setting would I have to set for the webserver to go missing ?

The most likely cause for the modem's web server to "go missing" is:
1. That specific model of cable modem simply doesn't have a web server.
Unusual, but not unheard of. Back in the 1990's, Toshiba cable modems
were examples of devices that didn't have internal web servers.

2. If you have a combo modem-router, you won't have a standalone cable
modem web server. It'll either be integrated into the router interface
or it simply won't be accessible to you on the LAN side of the device.

If you really want to see what's going on, check with your ISP about
purchasing your own cable modem and router. Be sure to look at getting
separate devices for those two functions. Then you'll have all of the
logs and visibility that you've been asking for.

Also surely the IP address assigned to this webserver would be resetted if I reset the cable modem ?!

No. The WAN-side IP address of a cable modem is mapped to its MAC
address, so resetting the cable modem will always result in getting the
same WAN-side IP, not that it does you any good since you can't access
the modem via that IP.

Even if not I already tried a scan of 192.168.x.x

However this can be done partiually...

later on the cable modem gets an ip from coax/isp. and this can no longer function... even windows refuses to send packets out, however the scan program happily continues.

One possibility to keep the cable modem operating at IP range 192.168.x.x would be to disconnect it from the internet by removing the coax cable.

I may try this later to perform an IP scan range on this device.

I do remember re-assing 192.168.100.1 to something more reasonable 0.100 or something or 0.254

But now I can't remember, apperently didn't document it, maybe it was even on different modem but I think it was on this.

May have to replace this modem cause not being able to enter it is kinda ****ty... and weird... hack concerns also.

If the device belongs to the ISP, it's not weird at all. Buy your own
equipment (and stop paying their monthly rental fee) in order to get
more control.

Wish somebody could read out it's memory contents and check if it was hacked or so.

I used to do that back in 2006, but not to see if the modem was hacked
but rather to make sure it was hacked. You shouldn't do that, though. In
my case, the modems belonged to me, not to the ISP. The keyword is
"JTAG".

Another hypo is that ISP tried some experimental software update and it somehow failed.

Not at all likely. ISPs don't try experimental software on their
customer base. Things can and do go wrong from time to time, but I
wouldn't call it experimental.

Or my vaccum cleaner killed parts of it... still strange that it's functioning perfectly except the menu... seems more human intervention then by chance.

You've never mentioned whether you can access the router menu in that
device, and if so, whether the router menu includes one or more pages
for the modem side of the device.

I strongly assume the answer to the first part is yes, and that alone
would have confirmed to you that the device is a combo modem-router and
not simply a modem.