In a CentOS 7 server, I type in firewall-cmd --list-all, and it gives me the following:  public (default, active)  interfaces: enp3s0  sources:   services: dhcpv6-client https ssh  ports:   masquerade: no  forward-ports:   icmp-blocks:   rich rules:What is the dhcpv6-client service?  What does it do?  And what are the implications of removing it? I read the wikipedia page for dhcpv6, but it does not tell me specifically what this service on CentOS 7 Firewalld does.  This server is accessible via https and email via mydomain.com, but it is a private server that can only be accessed via https by a list of known ip addresses.  In addition, this server can receive email from a list of known email addresses.  Is the dhcpv6-client service required to reconcile the domain addresses from the known ip https requests and for exchanging the email with known email addresses?
what is dhcpv6-client service in firewalld, and can i safely remove it?
centos;firewall;dhcp;firewalld
This is needed if you are using DHCP v6 due to the slightly different way that DHCP works in v4 and v6.In DHCP v4 the client establishes the connection with the server and because of the default rules to allow 'established' connections back through the firewall, the returning DHCP response is allowed through.However, in DHCP v6, the initial client request is sent to a statically assigned multicast address while the response has the DHCP server's unicast address as the source (see RFC 3315).  As the source is now different to the initial request's destination, the 'established' rule will not allow it through and consequently DHCP v6 will fail.To combat this, a new firewalld rule was created called dhcpv6-client which allows incoming DHCP v6 responses to pass - this is the dhcpv6-client rule.  If you're not running DHCP v6 on your network or you are using static IP addressing, then you can disable it.