computer not seeing modem through ethernet switch

Discussion in 'Computing and Networks' started by xtal_01, May 17, 2019.

  1. Yaakov

    Well-Known Member

    Jan 27, 2019
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    We'll have to leave this at disagreement.
     
  2. eetech00

    Senior Member

    Jun 8, 2013
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    Agreed..:D
     
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Yeah, but if you are going to use a hosts file, you wouldn’t use an IP address to access the modem. You would use the host name! Otherwise, it’s not smart.

    The problem seems to be that the browser is NOT recognizing the IP address as an IP address. You say it should... But it doesn’t. This problem is not unique to the TS.
    https://stackoverflow.com/questions...ress-is-entered-directly-into-the-address-bar

    So give the modem a DNS name and always access it with that name. What’s wrong with that?
     
  4. eetech00

    Senior Member

    Jun 8, 2013
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    :rolleyes: Here we go again...

    If the browser can’t do that it’s worthless...

    That’s basically what placing a name the host file does except its used locally and doesn’t require DNS.

    eT
     
  5. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Obviously, you don’t understand what I said.

    Saying a browser is worthless contributed nothing to the discussion nor does it change reality.

    Did I say anything about requiring DNS?

    I aced the networking certification exam. I designed/ built/ maintained a $20M/month e-commerce site that broke the network down into 7 sub networks separated by redundant firewalls and redundant application layer firewalls. With redundant routers and switches in a three tier network design. It passed the strictest PCI DSS certification level (the same that banks and financial institutions must meet). Met 99.999% uptime contractual requirements. Also, duplicated the entire environment on the west coast in a warm server site. All transactions were duplicated on both coasts in real time. All the while processing 30,000 transactions/sec.

    Just curious. What are your qualifications?

    I’ll be nice and agree to disagree as well.
     
    Last edited: May 19, 2019
  6. eetech00

    Senior Member

    Jun 8, 2013
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    Sorry...Its hard for me to understand what you don't properly explain.
    For example, what the heck does this mean?....

    "Yeah, but if you are going to use a hosts file, you wouldn’t use an IP address to access the modem. You would use the host name! Otherwise, it’s not smart."

    It does contribute....It means it isn't the browser.

    Yes.....Perhaps you like to explain how to give it a DNS name?

    Nice experience....congratulations..

    I've been integrating/engineering computer systems and networks for over 30 years. including various firewalls, switches, routers, WANs, email systems, both Unix/linux and all MS sever systems including 2016, Azure...and too many others to mention here without boring everyone. If you want to know more you can PM me if you like.

    eT
     
  7. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    I;ll go back later and read the thread. I'll start with:

    because I THINK it's an easy question.

    You have to pay attention to the "stupid little lights" around the Ethernet port.

    You likely don't have the green light on the port with the modem attached to the switch?

    So, my answer is:

    A port somewhere is not auto-MIDX or you need a CROSSOVER CABLE.

    If the switch has a WAN port, it will essentially be crossed. Us it for the device that doesn't give you a green light,

    In the old days with 10-BT switches and no auto-MIDX ports, a 7-port hub had 8 ports. one was shared and was an uplink port. It had a crossover type wiring. 10-Bt only had 2 pairs.

    By DEFINITION Gigabit ports are auto-MIDX. A 4 Pr Gigabit crossover cable is not supposed to cross the spare pair.

    I had one stupid device, a print server at home that did not like the cross-over cable direct to the laptop. It insisted that it needed a hub/switch./
     
  8. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    FYI.

    A ping to 224.0.0.1 (multicast address) and then an arp -a
    will often bring up most of the addresses on the network. including one that don't belong there.

    if a device is assigned a link local address:

    Link-local addresses for IPv4 are defined in the address block 169.254.0.0/16 in CIDR notation. In IPv6, they are assigned the address block fe80::/10.[2]

    https://en.wikipedia.org/wiki/Link-local_address

    Then there is no DHCP server.

    -=---

    Incidently 127.0.0.1 is localhost or the device that your doing a ping to. A ping to 127.0.0.1 from your computer is always your computer. When you had to install the network stack, that was the first test.

    ==


    FWIW: You might want to look at AWS. https://aws.amazon.com/
    Because you generally can't get to the other location unless it has an assigned IP address, both sides end up using dynamic DNS, Home internet doesn't get a permanent IP address. It gets it from a pool. that pool changes, so your IP address keeps changing.

    You MIGHT find out that you can;t reach the cellular modem from the internet, but the cellular modem can access the Internet. Hence the cloud approach.

    A thermostat publishes data to a cloud and you go on the Internet to get that published data. Two devices might do the same. I have no idea how it all works, but I've been reading.
     
    Last edited: May 21, 2019
  9. xtal_01

    Thread Starter Member

    May 1, 2016
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    OK .... it has been almost a month.

    I have fought with this darn thing and with tech support ... watched youtube videos ... read page on page .....

    I am sooooooo close!

    Lots of little things (apn # erased after flash, apn given to me with spelling mistake, SIMM card problem, antenna problem, ....).

    So over the weekend I finally got it to connect to Verizon!

    Now I have a new problem I have been fighting and just don't understand enough ... and can't find a good explanation on the web.

    Here is the location of the online manual: https://support.advantech-bb.com/download/sr/1-HIPH-380

    So, first I followed example 1 page 63 .... I checked "send all remaining incoming packets to ..... 192.168.1.2" ... which just happens to be the IP that came up when I did a "ipconfig" in the command prompt window of my computer.

    It works! I was able to use the Remote desktop function in computers (one at home and one on the cellular modem) to connect.

    Now the problem ... I have (or will have) two devices (a plc and a touch panel HMI) to connect to the cellular modem.

    I tried to follow example 2 (page 64 - 65) .... no luck.

    I unchecked "send all remaining ..."

    I entered "81" 80" "TCP" "192.168.1.2" into the table ... no luck.

    After watching a youtube video, I entered "3389" "3389" "TCP" "192.168.1.2" ... it worked! Again I could connect the two computers via remote desktop.

    If I try any other number other then 3389, it does not work.

    So, how do you get two devices to work?

    I will assign two different internal IP addresses (one to the PLC and one the touch screen) ... for the sake of argument lets say I manually enter 192.168.1.5 (for the PLC) and 192.168.1.6 (for the touch screen) ... I am guessing these are valid values.

    How will I enter these into the table?

    Can they both have the same port # (just different IP addresses)?

    Why is 3389 working (got it off a youtube video) ... why not 80 as in the example?

    Mike
     
  10. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    IP addresses identify different devices

    Ports (like 3389) identify different functions or services on a device.

    Routers let you map different devices and different ports to another device and another port.

    3389 happens to be the port for Remote Desktop Services. You need one device with software that sends on port 3389 to another device that is listening on port 3389. The device you wish to connect to with RDP, must have software that listens on port 3389.

    This doesn’t apply to you, but for security, oftentimes port 3389 is changed. This is since everyone knows what port 3389 is used for, hackers try to scan your IP addresses with port 3389 to take control of your assets.
     
  11. xtal_01

    Thread Starter Member

    May 1, 2016
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    So, are you saying that when I want to connect my PLC and Touch panel to the cellular modem, I should use port 80?

    In the example, they use "private" vs "public" ports.

    The private ports are all "80" and he public ports all different "81", "82". "83", ....

    If "80" is the right port ... can I just put all the ports (all public and private ports) in the NAT table as "80"?

    Thanks again ..... Mike
     
  12. eetech00

    Senior Member

    Jun 8, 2013
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    A picture is worth a thousand words. :)

    Draw a diagram of your network showing all physical device connections. Name each device and identify their ports with a number on the diagram. Post the diagram. This will help eliminate a lot of guess work..

    Then let’s discuss...
     
  13. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I agree with eetech00. But, the port you use isn’t arbitrary. It depends on what you want to do between the PLC and Touch Pad. If it’s strictly browser access, then port 80 will work (http: protocol is by default on port 80). If it’s RDP, then you need port 3389 open. Or any other standard service, you’ll need the assigned port open.

    Think of it this way. You want to deliver a package to Jim in apt. 12 at 1 Elm St.
    • 1 Elm St is the address. Compare it to the IP address of your device.
    • Jim is in apt. 12. The port in this example would be 12.
    • Jim has to be home to accept the package. This represents the service software that runs on your device which listens to a port.
    You can’t connect via a browser if there isn’t something listening for an http: request. You can’t RDP to a machine if there’s nothing listening for data on port 3389. And does something with that data.
     
  14. xtal_01

    Thread Starter Member

    May 1, 2016
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    OK, I did a quick drawing and attached it to this e-mail.

    I hope it makes sense.

    The plc really is the interface with the outside world (its' I/O controls pumps, takes in 4-20 mA signals, ...). The touch screen provides the virtual switches for the plc. The plc reports back to the touch screen (indicates if pumps are on or off).

    Both the PLC and the touch screen can send out e-mails ... report if something is wrong.

    When on my home computer, I contact the cellular modem (it has a static IP address) through a browser window. When I do this, I should be able to control the HMI panel. It has software built in that lets you do this ... just like using a remote desktop.

    If you need more description, please just ask.

    Thanks .... Mike
     
  15. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    I want to try to help you understand something.

    http: is the Hypertext Transfer protocal. It occurs on a "well-known" port. So say 192.168.1.1 is an address of some device.

    http://192.168.1.1 is the same as 192.168.1.1:80

    If for some reason you have an http service running on port 8080, you have to specify the port and protocol. e.g. http://192.168.1.1:8080

    Sending mail has a specific port to. That one can be a bit more complicated. Your ISP might change the port number.

    Telnet is essentially a character based connection, Way back when I was able to send mail using the specific port commands to send mail when passwords were sent in the clear. I could also use my woors mail server to send mail from my computer from any ISP.

    ==

    When you add routers to the mess that don't have STATIC IP adddresses, you have to use a DymanicDNS service. An app on a router/computer will tell the dyndns website that your IP address has changed, It might assign you the domain name myproject.dyndns.org

    --

    Once you throw in a router that has a DYNAMIC IP address, NAT or Network Address Translation. That single public IP address has the port numbers. You have to assign incoming ports to specific computers in your private network. You cannot have two port 80's looking in from from outside. You can have an http service running on port 80 at 192.168.1.1 and also at 192.168.1.2:80 and re-direct them in the router.

    Within the local network you can have two port 80;s, just not from outside, 8080 can get re-diected to port 80- on one machine and 80 could be re-directed to 80 on another.

    Through the magic of NAT and MAC addresses, all outgoiing and incoming port messages, get your public IP address and ports to communicate.
     
  16. xtal_01

    Thread Starter Member

    May 1, 2016
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    I looked up a table of port addresses on Wikipedia ... I think it all makes sense.

    So I will need to know (say for the touch screen) 1) what the internal ip address is and 2) what protocol they are using to communicate with the touch screen.

    Just for the sake of arguments, lets say it was http ... then I would choose port 80.

    It this correct?

    Now just one question ... the PLC and touch screen can both send out e-mail alerts.

    They are "sending", not receiving e-mails. Do I still need to put them in the NAT table?

    If I do then I would enter their internal IP and put them on port 25 (or 2525 or 587 or 465 ... have not figured out why so many e-mail ports yet)?

    Thanks again ..... Mike
     
  17. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    That’s correct. You got it so far.

    You should be fine when sending messages on an outbound connection, all communication occur using that initial session.

    The multitude of ports are because email is more than a simple protocol. There are many to support a broad range of services. SMTP and POP are two and there are others and some servers use different ports for security. But all you need to know is the external email servers IP address and which port it can listen on.

    Side story: while working in IT security, I could test an email server with a laptop and a program like Telnet. It’s how Wikileaks hacked into our political email servers (both major parties).
     
    Last edited: Jun 4, 2019
  18. xtal_01

    Thread Starter Member

    May 1, 2016
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    Interesting .... well I will never be an expert on the subject .... hmmm ... I guess I might now qualify as a beginner ... but at least I think I understand enough to get this project off the ground.

    I will now order the PLC and touch panel ... cross my fingers and see if I can get everything talking!

    I am sure I will have more questions when I get these parts in.

    Thanks .... Mike
     
    djsfantasi likes this.
  19. avalonnetwork

    New Member

    Aug 17, 2019
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    How are you assigning an IP address ? Is the main question in comes in my mind.
    As, If the switch has a management address, the switch and modem may share the same default address but if both devices are running DHCP, there could be a conflict.
    That's how the computer can find the modem when going through the switches.
     
  20. Geff Rush

    New Member

    Sep 9, 2019
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    reboot the system and change the modem
     
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