systemd.networkd: DHCP and link-local address











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Is it possible to configure systemd-networkd in a way like on Windows i nterms of DHCP and link-local address?



I mean:




  • if address can be obtained from DHCP, then fine - we are done.

  • if getting address from DHCP fails, then backfall to 169.254.x.x.


Also similar to RFC3927.



I am bit surprised how LinkLocalAddressing= option works. It just overrides DHCP. With settings like:



[Match]
Name=eth0
KernelCommandLine=!nfsroot

[Network]
DHCP=ipv4
LinkLocalAddressing=yes


I get:



Dec 17 15:10:43 my-system systemd-networkd[1276]: eth0: IPv6 successfully enabled
Dec 17 15:10:44 my-system systemd-networkd[1276]: eth0: Gained carrier
Dec 17 15:10:44 my-system systemd-networkd[1276]: eth0: DHCPv4 address 10.114.138.133/24 via 10.114.138.1
Dec 17 15:10:45 my-system systemd-networkd[1276]: eth0: Gained IPv6LL
Dec 17 15:10:57 my-system systemd-networkd[1276]: eth0: Configured
root@my-system:~#
root@my-system:~# ifconfig
eth0 Link encap:Ethernet HWaddr 00:44:44:00:04:17
inet addr:169.254.184.36 Bcast:169.254.255.255
Mask:255.255.0.0









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  • Is not that the default behaviour?
    – Rui F Ribeiro
    yesterday















up vote
0
down vote

favorite












Is it possible to configure systemd-networkd in a way like on Windows i nterms of DHCP and link-local address?



I mean:




  • if address can be obtained from DHCP, then fine - we are done.

  • if getting address from DHCP fails, then backfall to 169.254.x.x.


Also similar to RFC3927.



I am bit surprised how LinkLocalAddressing= option works. It just overrides DHCP. With settings like:



[Match]
Name=eth0
KernelCommandLine=!nfsroot

[Network]
DHCP=ipv4
LinkLocalAddressing=yes


I get:



Dec 17 15:10:43 my-system systemd-networkd[1276]: eth0: IPv6 successfully enabled
Dec 17 15:10:44 my-system systemd-networkd[1276]: eth0: Gained carrier
Dec 17 15:10:44 my-system systemd-networkd[1276]: eth0: DHCPv4 address 10.114.138.133/24 via 10.114.138.1
Dec 17 15:10:45 my-system systemd-networkd[1276]: eth0: Gained IPv6LL
Dec 17 15:10:57 my-system systemd-networkd[1276]: eth0: Configured
root@my-system:~#
root@my-system:~# ifconfig
eth0 Link encap:Ethernet HWaddr 00:44:44:00:04:17
inet addr:169.254.184.36 Bcast:169.254.255.255
Mask:255.255.0.0









share|improve this question







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  • Is not that the default behaviour?
    – Rui F Ribeiro
    yesterday













up vote
0
down vote

favorite









up vote
0
down vote

favorite











Is it possible to configure systemd-networkd in a way like on Windows i nterms of DHCP and link-local address?



I mean:




  • if address can be obtained from DHCP, then fine - we are done.

  • if getting address from DHCP fails, then backfall to 169.254.x.x.


Also similar to RFC3927.



I am bit surprised how LinkLocalAddressing= option works. It just overrides DHCP. With settings like:



[Match]
Name=eth0
KernelCommandLine=!nfsroot

[Network]
DHCP=ipv4
LinkLocalAddressing=yes


I get:



Dec 17 15:10:43 my-system systemd-networkd[1276]: eth0: IPv6 successfully enabled
Dec 17 15:10:44 my-system systemd-networkd[1276]: eth0: Gained carrier
Dec 17 15:10:44 my-system systemd-networkd[1276]: eth0: DHCPv4 address 10.114.138.133/24 via 10.114.138.1
Dec 17 15:10:45 my-system systemd-networkd[1276]: eth0: Gained IPv6LL
Dec 17 15:10:57 my-system systemd-networkd[1276]: eth0: Configured
root@my-system:~#
root@my-system:~# ifconfig
eth0 Link encap:Ethernet HWaddr 00:44:44:00:04:17
inet addr:169.254.184.36 Bcast:169.254.255.255
Mask:255.255.0.0









share|improve this question







New contributor




coulomb is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











Is it possible to configure systemd-networkd in a way like on Windows i nterms of DHCP and link-local address?



I mean:




  • if address can be obtained from DHCP, then fine - we are done.

  • if getting address from DHCP fails, then backfall to 169.254.x.x.


Also similar to RFC3927.



I am bit surprised how LinkLocalAddressing= option works. It just overrides DHCP. With settings like:



[Match]
Name=eth0
KernelCommandLine=!nfsroot

[Network]
DHCP=ipv4
LinkLocalAddressing=yes


I get:



Dec 17 15:10:43 my-system systemd-networkd[1276]: eth0: IPv6 successfully enabled
Dec 17 15:10:44 my-system systemd-networkd[1276]: eth0: Gained carrier
Dec 17 15:10:44 my-system systemd-networkd[1276]: eth0: DHCPv4 address 10.114.138.133/24 via 10.114.138.1
Dec 17 15:10:45 my-system systemd-networkd[1276]: eth0: Gained IPv6LL
Dec 17 15:10:57 my-system systemd-networkd[1276]: eth0: Configured
root@my-system:~#
root@my-system:~# ifconfig
eth0 Link encap:Ethernet HWaddr 00:44:44:00:04:17
inet addr:169.254.184.36 Bcast:169.254.255.255
Mask:255.255.0.0






networking systemd systemd-networkd






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  • Is not that the default behaviour?
    – Rui F Ribeiro
    yesterday


















  • Is not that the default behaviour?
    – Rui F Ribeiro
    yesterday
















Is not that the default behaviour?
– Rui F Ribeiro
yesterday




Is not that the default behaviour?
– Rui F Ribeiro
yesterday










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Try using "ip addr show" rather than ifconfig. I suspect that this will show you two IP addresses:




  1. the link local address; and

  2. the DHCP assigned IP address.


systemd-networkd is not "overriding" the DHCP assigned address with the link local address. Both addresses are active and working. It's just that ifconfig is only capable of showing a single IP address on the interface and it shows you the first address that it sees, ignoring any others.



ifconfig is already deprecated. It's time to switch to using the ip utility instead... Here's a cheat sheet that might help:
https://access.redhat.com/sites/default/files/attachments/rh_ip_command_cheatsheet_1214_jcs_print.pdf






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    Try using "ip addr show" rather than ifconfig. I suspect that this will show you two IP addresses:




    1. the link local address; and

    2. the DHCP assigned IP address.


    systemd-networkd is not "overriding" the DHCP assigned address with the link local address. Both addresses are active and working. It's just that ifconfig is only capable of showing a single IP address on the interface and it shows you the first address that it sees, ignoring any others.



    ifconfig is already deprecated. It's time to switch to using the ip utility instead... Here's a cheat sheet that might help:
    https://access.redhat.com/sites/default/files/attachments/rh_ip_command_cheatsheet_1214_jcs_print.pdf






    share|improve this answer








    New contributor




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      up vote
      0
      down vote













      Try using "ip addr show" rather than ifconfig. I suspect that this will show you two IP addresses:




      1. the link local address; and

      2. the DHCP assigned IP address.


      systemd-networkd is not "overriding" the DHCP assigned address with the link local address. Both addresses are active and working. It's just that ifconfig is only capable of showing a single IP address on the interface and it shows you the first address that it sees, ignoring any others.



      ifconfig is already deprecated. It's time to switch to using the ip utility instead... Here's a cheat sheet that might help:
      https://access.redhat.com/sites/default/files/attachments/rh_ip_command_cheatsheet_1214_jcs_print.pdf






      share|improve this answer








      New contributor




      the_kid is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.




















        up vote
        0
        down vote










        up vote
        0
        down vote









        Try using "ip addr show" rather than ifconfig. I suspect that this will show you two IP addresses:




        1. the link local address; and

        2. the DHCP assigned IP address.


        systemd-networkd is not "overriding" the DHCP assigned address with the link local address. Both addresses are active and working. It's just that ifconfig is only capable of showing a single IP address on the interface and it shows you the first address that it sees, ignoring any others.



        ifconfig is already deprecated. It's time to switch to using the ip utility instead... Here's a cheat sheet that might help:
        https://access.redhat.com/sites/default/files/attachments/rh_ip_command_cheatsheet_1214_jcs_print.pdf






        share|improve this answer








        New contributor




        the_kid is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.









        Try using "ip addr show" rather than ifconfig. I suspect that this will show you two IP addresses:




        1. the link local address; and

        2. the DHCP assigned IP address.


        systemd-networkd is not "overriding" the DHCP assigned address with the link local address. Both addresses are active and working. It's just that ifconfig is only capable of showing a single IP address on the interface and it shows you the first address that it sees, ignoring any others.



        ifconfig is already deprecated. It's time to switch to using the ip utility instead... Here's a cheat sheet that might help:
        https://access.redhat.com/sites/default/files/attachments/rh_ip_command_cheatsheet_1214_jcs_print.pdf







        share|improve this answer








        New contributor




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