Can anybody reach their NR7101 settings pages/GUI via LAN (ethernet cable)

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  • tonygibbs16
    tonygibbs16 Posts: 945  Guru Member
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    edited May 2023

    Hello @k1s

    Ok.

    The packet traffic says that there is no connection between 192.168.254.1 and 192.168.254.71

    Which seems like a routing issue.

    The ZTE modem is asking using ARP, so the issue might not be there.

    I wonder if adding a static route on the NR7101 as per section 10.2 of the user guide at https://download.zyxel.com/NR7101/user_guide/NR7101_Version%201.00.pdf might help.

    - I think that it would be 192.168.254.1 subnet mask 255.255.255.0 gateway 192.168.1.1

    Adding a static route should at least tell the NR7101 where to find your ZTE modem.

    Could you try this please and then re-run the tcpdump and Ping?

    Kind regards,

    Tony

  • k1s
    k1s Posts: 73  Ally Member
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    "The packet traffic says that there is no connection between 192.168.254.1 and 192.168.254.71"

    There doesn't need to be. These are two separate 5G modems - one (192.168.254.1, ZTE) is providing 'the internet' into the LAN's primary router (192.168.1.1) via one of the two WAN ports that can receive WAN/internet traffic. The other device (192.168.254.71) is the NR7101, which is supposed to be a 2nd/backup "source of internet" . The primary router (a Synology RYT6600ax) handles this - i.e. two independent internet connections, which it can load balance or simply switch between as failover. In either case, neither modem needs to be able to talk to each other or even see each other.

    So, just to recap, I don't need the two modems to talk with each other, I'm just trying to reach the NR7101 through the LAN.

    (If I can reach the ZTE modem from any PC on the lan simply by entering it's IP, without any static routes through the router, I was assuming I could do the same with the NR7101, but I guess there is something about the NR7101 that is configured out of the box differently than with the ZTE modem, which is causing it not to be seen 'plug & play' like the ZTE modem… )

  • tonygibbs16
    tonygibbs16 Posts: 945  Guru Member
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    edited May 2023

    Hello @k1s

    Thanks for your reply.

    If you want the NR7101 to have a 192.168.254.71 IP address then I think that there does need to be a connection and route between the NR7101 and the ZTE modem.

    If you don't, then that is up to you.

    If you add the static route on the NR7101 and it works, then you could have want you want, namely access to the NR7101 web configurator from your LAN.

    What would you like?

    Kind regards,

    Tony

  • k1s
    k1s Posts: 73  Ally Member
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    "If you want the NR7101 to have a 192.168.254.71 IP address then I think that there does need to be a connection and route between the NR7101 and the ZTE modem."

    Why would they need to talk to each other?

  • tonygibbs16
    tonygibbs16 Posts: 945  Guru Member
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    edited May 2023

    Hello @k1s

    https://community.zyxel.com/en/discussion/comment/52733#Comment_52733

    I think that it is because your primary LAN router is using your ZTE modem as the next hop for reaching any address on the 192.168.254.0/24 subnet.

    The tcpdump log seems to be indicating this, because your ZTE modem is asking by ARP what the MAC address of the NR7101 is, so that it can communicate with it.

    Kind regards,

    Tony

  • k1s
    k1s Posts: 73  Ally Member
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    "your primary LAN router is using your ZTE modem as the next hop for reaching any address on the 192.168.254.0/24 subnet".

    How does it make the first hop, without any help? Couldn't it do the same for any other on the 192.168.254.0/24 subnet? The ZTE modem doesn't have any routing capability enabled (no DHCP, no router functions. As far it's concerned its a dumb modem.), so I'm not sure why's it's 'asking by ARP what the MAC address of the NR7101'. I

  • tonygibbs16
    tonygibbs16 Posts: 945  Guru Member
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    edited May 2023

    Hello @k1s

    https://community.zyxel.com/en/discussion/comment/52967#Comment_52967

    A router has to work out the next hop for the routing of IP datagrams, by comparing the destination IP address with what is in its routing table, see http://www.cs.cornell.edu/courses/cs4410/2015su/lectures/lec23-routing.html#:~:text=To%20determine%20the%20next%20hop,first%20next%2Dhop%20that%20matches.

    So I think that your primary LAN router will have 192.168.254.0 with subnet mask 255.255.255.0 in its routing table, and so sends every datagram for the 192.168.254.0 subnet to a device on that network.

    Once your ZTE modem receives an IP datagram for a host on its subnet, then it has try find the host on its subnet by ARP, and reply destination unreachable if it does not get a reply.

    Your ZTE modem is not completely dumb, because it has to have the ability to route datagrams at OSI-RM layer 3 / IP layer. Your ZTE modem has to be able to transmit and receive IP datagrams between Ethernet and LTE/3GPP and that is a routing function.

    Your ZTE modem also has to be able to find other hosts on its own subnet, which is what it is doing.

    I hope that this is helpful.

    Kind regards,

    Tony

  • tonygibbs16
    tonygibbs16 Posts: 945  Guru Member
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    edited May 2023

    Hello @k1s

    Something else you could try if you wish, is putting the NR7101 into Router mode.

    You could make it give out a DHCP address in the 192.168.254.0 network with the LAN DHCP pool set so that it starts as 192.168.254.3

    You could then give your NR7101 a static IP address of 192.168.254.2 with subnet mask of

    255.255.255. 0

    This might allow both your ZTE modem and primary LAN router to find it and you could see if your NR7101 now responds to ping and allows you to manage it.

    I appreciate that this will be hard for you to setup, since your NR7101 is high up on a mount. You might want to bring your NR7101 device down to a more convenient height until it is working fully for you ...

    I hope that this is helpful.

    Kind regards, Tony

  • k1s
    k1s Posts: 73  Ally Member
    First Answer First Comment Friend Collector Second Anniversary

    Thanks for the suggestions, I'll give them a go at the

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