Wireless Access Point using a modem connection is not working correctly, probably due to MTU

Wim Van Geem

3/21/24, 10:18 AM

With netplan, I created a modem connection:

network:
 version: 2
 renderer: NetworkManager
 modems:
  cdc-wdm0:
   optional: false
   dhcp4: true
   auto-config: true
   pin: 2832
   apn: internet.proximus.be

I also created a wireless access point

network:
 version: 2
 renderer: NetworkManager

     # Wireless configuration
     wifis:
      wlp2s0:
       dhcp4: true
       optional: false
       access-points:
        DCA632784996:
         mode: ap

On the server itself, I can perfectly ping to www.google.be (using the modem connection), and browse to whatever site I want.

When I connect with another device (mobile phone, or other ubuntu) through the access point, I can ping to www.google.be, I can search in Google and get results, but I cannot browse to other sites.

I already had problems with MTU on this server for another project, since the modem has an MTU of 1430. So I changed both netplan configurations:

network:
 version: 2
 renderer: NetworkManager
 modems:
  cdc-wdm0:
   optional: false
   dhcp4: true
   auto-config: true
   pin: 2832
   apn: internet.proximus.be
   mtu: 1429

and

network:
 version: 2
 renderer: NetworkManager

     # Wireless configuration
     wifis:
      wlp2s0:
       dhcp4: true
       optional: false
       mtu: 1429
       access-points:
        DCA632784996:
         mode: ap

If I check my interfaces (ip addr show), the wlp2s0 show mtu=1429

But this doesn't solve the problem. I believe the "client" still tries to send packages with MTU 1500, although it connects to an access point with the MTU set to 1429.

Any idea how this could be resolved?

0 + 0

network-manager

modem

wireless-access-point

Elon Musk

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EN: Wireless Access Point using a modem connection is not working correctly, probably due to MTU

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