Question Cascading two modems lan-to-lan[A WEIRD PROBLEM]

Jun 16, 2020
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Hello everyone. Long story short, i cascaded my ISP provided modem( ZTE ZXHN H298A) with TP-LINK Archer vr300(this will be second modem) via lan to lan connection in order to extend my wifi range. I turned off the DHCP server on the tplink and turn off all the firewalls on both modems and unpnp and nat. I choose different channels and same SSID, same passwords. So instead of simultanious switch between first and second router depending on the signal strength, when my devices tries to switch from 1st to 2nd modem, it fails and no internet connection. It looks like it is connected but no internet access. From 2nd modem to 1st modem is just fine, no problem. So then i thought that i can change the SSID and make them seperate and switch back and forth manually, so i did that. Now, if i disconnect from 2nd router and connect to the 1st, it is ok, but if i try to disconnect from 1st and join the 2nd, it fails. I have to try for like 10 minutes and then it connects. So my real problem is that i have experiencing a connection issues to my 2nd modem and i dont know why, i factory resset it like a dozen of times. Also in the interface of the second modem it shows that no internet connection but in fact there is internet connection and i can use it fine if i can connect.

Side note: I was using this TPLINK modem as my primary and there was no issues at all. So it is not a hardware related problem. But now, i have to use the ISP provided modem for my internet access.
 
Jun 16, 2020
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I never heard about this before. Will def check out. Because i am having the hardest time while trying to connect my pcs, phones are connect eventually. But the thing is, even if i change the ssid and make it different seperate network, i still get connection errors.
 

Ralston18

Titan
Moderator
Connections being:

ISP ---->ZTE Modem [LAN]---ethernet cable --->[LAN port] TP-Link[LAN Port] ---> Ethernet cable to wired devices and ~~~~> wireless to wireless devices.

Edit and correct my line diagram as necessary.

ZTE Modem has DHCP off - correct? Only one modem/router should have DHCP enabled.

Separate network(s) - what IP addresses and ranges are you using? Subnet masks?

Frequency and channels being used?

How many devices: wired, wireless....?
 
Last edited:
Jun 16, 2020
9
0
10
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Connections being:

ISP ---->ZTE Modem [LAN]---ethernet cable --->[LAN port] TP-Link[LAN Port] ---> Ethernet cable to wired devices and ~~~~> wireless to wireless devices.

Edit and correct my line diagram as necessary.

ZTE Modem has DHCP off - correct? Only one modem/router should have DHCP enabled.

Separate network(s) - what IP addresses and ranges are you using? Subnet masks?

Frequency and channels being used?

How many devices: wired, wireless....?
diagram is correct. But DHCP is on on ZTE modem and Off on TPLINK

192.168.1.1 is ZTE’s ip and 192.168.1.2 is for TPLINK.

Both are using 5ghz and channels are auto(I tried set them to different channels but it did not have any difference)

4-5 devices
 
What happens if you use static ip on your pc. This would eliminate any dhcp type issues but dhpc is not active on both device so it really can't be that.

This looks like some kind of bug. Almost like the mac address is being mapped to the wrong port and it takes a while for it to time out.

Have you tried a ethernet cable and moved it from router to router. I can't see why wifi would be any different since the radio chip is internally connected to the switch chip.
 
Jun 16, 2020
9
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What happens if you use static ip on your pc. This would eliminate any dhcp type issues but dhpc is not active on both device so it really can't be that.

This looks like some kind of bug. Almost like the mac address is being mapped to the wrong port and it takes a while for it to time out.

Have you tried a ethernet cable and moved it from router to router. I can't see why wifi would be any different since the radio chip is internally connected to the switch chip.
dhcp is active on the main router. If i try to use cable from my pc to second router. It works fine but wirelessly i cannot use it. Actually i managed to connect from my other pc wirelessly too. So it is just my laptop does not connects to wifi. And i checked both modems to see if there is any blacklist for my pc but no, blacklisting feature is even turned off. So it really is a strange and stupid bug...
 

Ralston18

Titan
Moderator
Yes:

Just as you applied "ipconfig /all" simply type "arp -a" instead.

From my computer:

PS C:\WINDOWS\system32> arp -a
Interface: 192.168.1.107 --- 0xb
Internet Address Physical Address Type
192.168.1.1 94-10-3e-00-34-95 dynamic
192.168.1.100 00-1e-8f-99-ef-d1 dynamic
192.168.1.101 00-90-a9-b3-79-bc dynamic
192.168.1.255 ff-ff-ff-ff-ff-ff static
224.0.0.2 01-00-5e-00-00-02 static
224.0.0.22 01-00-5e-00-00-16 static
224.0.0.251 01-00-5e-00-00-fb static
224.0.0.252 01-00-5e-00-00-fc static
239.255.255.250 01-00-5e-7f-ff-fa static
255.255.255.255 ff-ff-ff-ff-ff-ff static
PS C:\WINDOWS\system32>

For more information about macs":

https://www.geeksforgeeks.org/introduction-of-mac-address-in-computer-network/
 
Last edited:
Jun 16, 2020
9
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Yes:

Just as you applied "ipconfig /all" simply type "arp -a" instead.

From my computer:

PS C:\WINDOWS\system32> arp -a
Interface: 192.168.1.107 --- 0xb
Internet Address Physical Address Type
192.168.1.1 94-10-3e-00-34-95 dynamic
192.168.1.100 00-1e-8f-99-ef-d1 dynamic
192.168.1.101 00-90-a9-b3-79-bc dynamic
192.168.1.255 ff-ff-ff-ff-ff-ff static
224.0.0.2 01-00-5e-00-00-02 static
224.0.0.22 01-00-5e-00-00-16 static
224.0.0.251 01-00-5e-00-00-fb static
224.0.0.252 01-00-5e-00-00-fc static
239.255.255.250 01-00-5e-7f-ff-fa static
255.255.255.255 ff-ff-ff-ff-ff-ff static
PS C:\WINDOWS\system32>

For more information about macs":

https://www.geeksforgeeks.org/introduction-of-mac-address-in-computer-network/
ok. this is the arp -a result from my computer. Right now i can connect the internet because yesterday i connected after waiting. So i don't know if i have connection issues again this results will be changed or not.

Interface: 192.168.1.20 --- 0x12
Internet Address Physical Address Type
192.168.1.1 e0-19-54-1d-17-18 dynamic
192.168.1.255 ff-ff-ff-ff-ff-ff static
224.0.0.2 01-00-5e-00-00-02 static
224.0.0.22 01-00-5e-00-00-16 static
224.0.0.251 01-00-5e-00-00-fb static
224.0.0.252 01-00-5e-00-00-fc static
239.255.255.250 01-00-5e-7f-ff-fa static
 

Ralston18

Titan
Moderator
Yes. Run "arp -a" every so often.

And keep as many devices active as possible on your network.

Do give all the devices time to "catch up" to the overall network configuration.

Right now your computer is assigned and is using 192.168.1.20 for its' dynamic IP address.

Log into your router and look for a list/display of network devices. There should be no IP duplicates.
 
Jun 16, 2020
9
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10
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Yes. Run "arp -a" every so often.

And keep as many devices active as possible on your network.

Do give all the devices time to "catch up" to the overall network configuration.

Right now your computer is assigned and is using 192.168.1.20 for its' dynamic IP address.

Log into your router and look for a list/display of network devices. There should be no IP duplicates.
I did check if there is any duplicates. I can’t find any. There is literally anything left to do i guess. But if i connect to other network and try to switch back to this one again(second router) i have to wait for 3 minutes and then it is fine.
 
These are the issues where it would be nice if the wifi chipset had any troubleshooting information. You could then see what is different. For some reason they do not provide this feature on consumer grade devices.

The only real difference between the 2 is that the encryption keys are different when you are talking to a different radio. It does take a small amount of time to restart but it should be less than 1 second.

Can you tell if you get connect to the radio but it does not work or if it is not connecting to the second radio.

If it does connect I assume you can not ping 192.168.1.1. What happens if you clear the arp table and then ping 192.168.1.1. Even if it fails does the arp entry for 192.168.1.1 reappear.
 

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