I have a server that receives its IP address by DHCP. This seems to work and the connectivity is working (at the moment). However, I have not rebooted since installing a new
/etc/sysconfig/iptables file so I could lose big upon the next reboot in case DHCP functionality depends on the connections now blocked.
I have noticed that my firewall blocks outgoing UDP DHCP connections like this one:
[22994.373788] Firewall: *UDP_OUT Blocked* IN= OUT=enup0 SRC=$OUR_IP DST=$DHCP_SERVER_IP LEN=328 TOS=0x00 PREC=0x00 TTL=64 ID=53942 DF PROTO=UDP SPT=68 DPT=67 LEN=308 UID=0 GID=0
This is presumably some DHCP client command like the request for a renewal of the DHCP lease?
What happens if I block this outgoing request? If that is DHCP server implementation dependent: Does perhaps an RFC document demand I do not block this?
Related: Do the firewall rules get initialised from
iptables.service) before or after the network is brought up during boot?
I wish to block as much as possible otherwise I would just allow it instead of asking here.