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nstuyvesant avatar Ubuntu

Disable both IPv4 and IPv6 on a specific interface

ag flag
nstuyvesant

Using Ubuntu 21.10, SoftEther docs recommend disabling IPv4 and IPv6 on one of the two Ethernet interfaces used for the local bridge network adapter.

Here's my /etc/netplan/01-network-manager-all.yaml...

network:
  version: 2
  renderer: NetworkManager
  ethernets:
    lan:
      match:
        macaddress: a8:20:XX:XX:9f:da
      dhcp4: false
      dhcp6: true
      addresses:
        - 192.168.1.3/24
      routes:
        - to: default
          via: 192.168.1.1
          metric: 100
      nameservers:
        addresses: [192.168.1.1]
        search: []
      set-name: lan
    softether:
      match:
        macaddress: 40:6c:XX:XX:4a:93
      dhcp4: false
      dhcp6: false
      link-local: []
      optional: true
      set-name: softether

then ran sudo netplan generate then sudo netplan apply. As you can see, I renamed the interface for the local bridge to softether.

Also added this to the end of /etc/sysctl.d/99-sysctl.conf

net.ipv6.conf.softether.disable_ipv6 = 1

then ran sudo sysctl -p.

After rebooting, I am still seeing an IPv4 and IPv6 addresses on softether when running ip a...

2: softether: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 40:6c:XX:XX:4a:93 brd ff:ff:ff:ff:ff:ff
    altname enp9s0
    inet 169.254.65.216/16 brd 169.254.255.255 scope link noprefixroute softether
       valid_lft forever preferred_lft forever
    inet6 fd8b:a698:e8f4:3:426c:8fff:fe35:4a93/64 scope global deprecated dynamic mngtmpaddr 
       valid_lft 769sec preferred_lft 0sec
    inet6 fd97:65c2:6883:1:426c:8fff:fe35:4a93/64 scope global dynamic mngtmpaddr 
       valid_lft 1785sec preferred_lft 1785sec
    inet6 fda2:db11:4cad:2:426c:8fff:fe35:4a93/64 scope global deprecated dynamic mngtmpaddr 
       valid_lft 769sec preferred_lft 0sec
    inet6 fdaa:ed5f:f69b:4:426c:8fff:fe35:4a93/64 scope global deprecated dynamic mngtmpaddr 
       valid_lft 770sec preferred_lft 0sec
    inet6 fe80::426c:8fff:fe35:4a93/64 scope link 
       valid_lft forever preferred_lft forever

The Netplan docs show these examples...

Example to enable only IPv4 link-local: link-local: [ ipv4 ]
Example to enable all link-local addresses: link-local: [ ipv4, ipv6 ]
Example to disable all link-local addresses: link-local: [ ]

So I thought using the last one would give me what I wanted (but it didn't).

Any thoughts about what I'm doing wrong?

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nstuyvesant avatar Ubuntu
ag flag
nstuyvesant

Looks like the issue was the Netplan renderer of NetworkManager. After switching to networkd, I got the results I was looking for:

2: softether: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 40:6c:XX:XX:4a:93 brd ff:ff:ff:ff:ff:ff
    altname enp9s0

Here's my new /etc/netplan/01-network-manager-all.yaml:

network:
  version: 2
  renderer: networkd
  ethernets:
    lan:
      match:
        macaddress: a8:20:XX:XX:9f:da
      dhcp6: true
      addresses:
        - 192.168.1.3/24
      routes:
        - to: default
          via: 192.168.1.1
          metric: 100
      nameservers:
        addresses: [192.168.1.1]
        search: []
      set-name: lan
    softether:
      match:
        macaddress: 40:6c:XX:XX:4a:93
      optional: true
      # optional-addresses: []
      link-local: []
      set-name: softether
  wifis:
    wlp2s0:
#     match:
#       macaddress: 88:53:XX:XX:f0:75
      dhcp4: yes
      dhcp6: yes
      access-points:
        "Some SSID":
          password: "SOME PASSWORD"
#     set-name: wifi

Unfortunately, I can no longer rename the WiFi interface like I could with NetworkManager as networkd's wifis don't support match.

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ru flag
Thomas Ward
Actually, according to the documentation, netplan's `wifs` *does* support match, it's possible you're just not entering them correctly.
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us flag
slangasek
What IPs were you seeing when setting link-local: [] with NetworkManager? This may be a bug in NM or in netplan that we should track and fix.
1
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nstuyvesant avatar
ag flag
nstuyvesant
The results of my `ip a` for the softether interface are included in my original post - 169.254.65.216/16 plus 5 x ipv6 addresses. I submitted an ubuntu-bug based on the results I saw above.
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nstuyvesant avatar
ag flag
nstuyvesant
Regarding the Netplan wifi's, my renaming of the interface worked with NetworkManager as the renderer (the commented lines were not previously commented). After switching to networkd, I got the error "ERROR: wlp2s0: networkd backend does not support wifi with match:, only by interface name". I'm open to suggestions if you're seeing a mistake in one of the 3 commented lines.
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