Arch Linux

MichaelMocha

Member

Registered: 2025-05-23

Posts: 2

[SOLVED] Internet connection with Ipv6 is working but Ipv4 is failing.

I can still connect to arch wiki and forums but not several other sites. This problem appeared just after a pacman update and reboot. I have had a working system prior to this.
These are my current versions of systemd and arch.

systemd 259-2
linux 6.18.5.arch1-1

I am not sure what the issue is. Putting the output of the commands I looked at and my current configs for reference.

ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host noprefixroute 
       valid_lft forever preferred_lft forever
2: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 9c:6b:00:98:28:87 brd ff:ff:ff:ff:ff:ff
    altname enx9c6b00982887
    inet6 2600:1700:7b08:c230:9e6b:ff:fe98:2887/64 scope global dynamic mngtmpaddr noprefixroute 
       valid_lft 3474sec preferred_lft 3474sec
    inet6 fe80::9e6b:ff:fe98:2887/64 scope link proto kernel_ll 
       valid_lft forever preferred_lft forever
4: virbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc htb state UP group default qlen 1000
    link/ether 52:54:00:a2:ba:0f brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
       valid_lft forever preferred_lft forever
5: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether c8:a3:e8:86:8e:57 brd ff:ff:ff:ff:ff:ff
    inet6 2600:1700:7b08:c230:caa3:e8ff:fe86:8e57/64 scope global dynamic mngtmpaddr noprefixroute 
       valid_lft 3474sec preferred_lft 3474sec
    inet6 fe80::caa3:e8ff:fe86:8e57/64 scope link proto kernel_ll 
       valid_lft forever preferred_lft forever
6: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master virbr0 state UNKNOWN group default qlen 1000
    link/ether fe:54:00:62:ad:52 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fe62:ad52/64 scope link proto kernel_ll 
       valid_lft forever preferred_lft forever
7: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master virbr0 state UNKNOWN group default qlen 1000
    link/ether fe:54:00:d9:ba:32 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fed9:ba32/64 scope link proto kernel_ll 
       valid_lft forever preferred_lft forever

In ip a I see only ipv6 assigned to my ethernet and wifi enp8s0 and wlan0

networkctl
IDX LINK   TYPE     OPERATIONAL SETUP     
  1 lo     loopback carrier     unmanaged
  2 enp8s0 ether    routable    configured
  4 virbr0 bridge   routable    unmanaged
  5 wlan0  wlan     routable    configured
  6 vnet0  ether    enslaved    unmanaged
  7 vnet1  ether    enslaved    unmanaged

6 links listed.

My network configs are from https://wiki.archlinux.org/title/System … me_machine

From what I have read DHCP=yes should tell it to configure ipv4.
I have tried adding RequiredFamilyForOnline=ipv4 and =both yet after restarting systemd-networkd I still only get an ipv6 assigned.

/etc/systemd/network/20-wired.network

[Match]
Name=enp8s0

[Link]
RequiredForOnline=routable
RequiredFamilyForOnline=ipv4

[Network]
DHCP=yes

[DHCPv4]
RouteMetric=100

[IPv6AcceptRA]
RouteMetric=100

I can tell that this config is active by checking networkctl

networkctl status enp8s0
● 2: enp8s0
                   Link File: /usr/lib/systemd/network/99-default.link
                Network File: /etc/systemd/network/20-wired.network
                       State: routable (configured)
                Online state: offline
                        Type: ether
                        Path: pci-0000:08:00.0
                      Driver: r8169
                      Vendor: Realtek Semiconductor Co., Ltd.
                       Model: RTL8125 2.5GbE Controller
           Alternative Names: enx9c6b00982887
            Hardware Address: 9c:6b:00:98:28:87 (ASRock Incorporation)
                         MTU: 1500 (min: 68, max: 16362)
                       QDisc: fq_codel
IPv6 Address Generation Mode: eui64
    Number of Queues (Tx/Rx): 1/1
            Auto negotiation: yes
                       Speed: 1Gbps
                      Duplex: full
                        Port: tp
                     Address: 2600:1700:7b08:c230:9e6b:ff:fe98:2887
                              fe80::9e6b:ff:fe98:2887
                     Gateway: fe80::92d0:92ff:fe6d:f321
                         DNS: 2600:1700:7b08:c230::1
           Activation Policy: up
         Required For Online: yes
          DHCPv6 Client IAID: 0xa97a36d2
          DHCPv6 Client DUID: DUID-EN/Vendor:0000ab118d85b5cc378a3555
                Connected To: n/a on port 90:d0:92:6d:f3:21
                              n/a on port 90:d0:92:6d:f3:21

Jan 15 18:55:47 archlinux systemd-networkd[10309]: enp8s0: Link UP
Jan 15 18:55:47 archlinux systemd-networkd[10309]: enp8s0: Gained carrier
Jan 15 18:55:47 archlinux systemd-networkd[10309]: enp8s0: Gained IPv6LL
Jan 15 18:55:47 archlinux systemd-networkd[10309]: enp8s0: Configuring with /etc/systemd/network/20-wired.network.
Jan 15 18:55:48 archlinux systemd-networkd[10309]: enp8s0: DHCP: received delegated prefix 2600:1700:7b08:c23f::/64
Jan 15 19:10:32 archlinux systemd-networkd[13394]: enp8s0: Link UP
Jan 15 19:10:32 archlinux systemd-networkd[13394]: enp8s0: Gained carrier
Jan 15 19:10:32 archlinux systemd-networkd[13394]: enp8s0: Gained IPv6LL
Jan 15 19:10:32 archlinux systemd-networkd[13394]: enp8s0: Configuring with /etc/systemd/network/20-wired.network.
Jan 15 19:10:33 archlinux systemd-networkd[13394]: enp8s0: DHCP: received delegated prefix 2600:1700:7b08:c23f::/64

It looks like saying Ipv4 is required for online just relabeled it as offline while it still configured ipv6

I don't see any errors in systemd-networkd

systemctl status systemd-networkd
● systemd-networkd.service - Network Management
     Loaded: loaded (/usr/lib/systemd/system/systemd-networkd.service; enabled; preset: enabled)
     Active: active (running) since Thu 2026-01-15 19:10:32 CST; 9min ago
 Invocation: 6bd02c870ef3488eacdb10ddcb9917e7
TriggeredBy: ● systemd-networkd.socket
             ● systemd-networkd-resolve-hook.socket
             ● systemd-networkd-varlink.socket
       Docs: man:systemd-networkd.service(8)
             man:org.freedesktop.network1(5)
   Main PID: 13394 (systemd-network)
     Status: "Processing requests..."
      Tasks: 1 (limit: 74037)
   FD Store: 1 (limit: 512)
     Memory: 2.4M (peak: 7.2M)
        CPU: 46ms
     CGroup: /system.slice/systemd-networkd.service
             └─13394 /usr/lib/systemd/systemd-networkd

Jan 15 19:10:32 archlinux systemd-networkd[13394]: wlan0: Connected WiFi access point: WIFINAME (90:d0:92:6d:f3:28)
Jan 15 19:10:32 archlinux systemd[1]: Started Network Management.
Jan 15 19:10:32 archlinux systemd-networkd[13394]: enp8s0: Configuring with /etc/systemd/network/20-wired.network.
Jan 15 19:10:32 archlinux systemd-networkd[13394]: wlan0: Configuring with /etc/systemd/network/25-wireless.network.
Jan 15 19:10:33 archlinux systemd-networkd[13394]: enp8s0: DHCP: received delegated prefix 2600:1700:7b08:c23f::/64
Jan 15 19:10:33 archlinux systemd-networkd[13394]: wlan0: DHCP: received delegated prefix 2600:1700:7b08:c23e::/64
Jan 15 19:17:43 archlinux systemd-networkd[13394]: enp8s0: Lost carrier
Jan 15 19:17:43 archlinux systemd-networkd[13394]: enp8s0: DHCPv6 lease lost
Jan 15 19:17:49 archlinux systemd-networkd[13394]: enp8s0: Gained carrier
Jan 15 19:18:02 archlinux systemd-networkd[13394]: enp8s0: DHCP: received delegated prefix 2600:1700:7b08:c23f::/64

The 9 min ago uptime is from when I restarted systemd-networkd after editing the ethernet's config file.

Let me know if there is anything else I can test or try. Thanks.

Last edited by MichaelMocha (2026-01-16 16:11:34)

-thc

Member

Registered: 2017-03-15

Posts: 1,086

Re: [SOLVED] Internet connection with Ipv6 is working but Ipv4 is failing.

This

Jan 15 19:10:33 archlinux systemd-networkd[13394]: enp8s0: DHCP: received delegated prefix 2600:1700:7b08:c23f::/64

literally means your PC is acting as an IPv6 router which gets a delegated IPv6 prefix from your main router.

AFAIK this is only possible through DHCPv6 - you have to look at your DHCP client and configuration. There you may find a reason for your machine to not issue DHCPv4 requests.

MichaelMocha

Member

Registered: 2025-05-23

Posts: 2

Re: [SOLVED] Internet connection with Ipv6 is working but Ipv4 is failing.

Turns out I had the exact same issue on my windows laptop. Power cycling my router fixed the issue with Ethernet. Wifi says it is still configuring.

-thc

Member

Registered: 2017-03-15

Posts: 1,086

Re: [SOLVED] Internet connection with Ipv6 is working but Ipv4 is failing.

Turns out this:

https://www.youtube.com/watch?v=5UT8RkSmN4k

helps in quite an astonishing amount of cases.