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nstuyvesant
Asked: 2021-11-07 06:31:09 +0800 CST

Disable both IPv4 and IPv6 on a specific interface

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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?

ethernet

1 Answers

  1. Best Answer

    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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