+[[pve_firewall_default_rules]]
+Default firewall rules
+----------------------
+
+The following traffic is filtered by the default firewall configuration:
+
+Datacenter incoming/outgoing DROP/REJECT
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If the input or output policy for the firewall is set to DROP or REJECT, the
+following traffic is still allowed for all {pve} hosts in the cluster:
+
+* traffic over the loopback interface
+* already established connections
+* traffic using the IGMP protocol
+* TCP traffic from management hosts to port 8006 in order to allow access to
+ the web interface
+* TCP traffic from management hosts to the port range 5900 to 5999 allowing
+ traffic for the VNC web console
+* TCP traffic from management hosts to port 3128 for connections to the SPICE
+ proxy
+* TCP traffic from management hosts to port 22 to allow ssh access
+* UDP traffic in the cluster network to port 5404 and 5405 for corosync
+* UDP multicast traffic in the cluster network
+* ICMP traffic type 3 (Destination Unreachable), 4 (congestion control) or 11
+ (Time Exceeded)
+
+The following traffic is dropped, but not logged even with logging enabled:
+
+* TCP connections with invalid connection state
+* Broadcast, multicast and anycast traffic not related to corosync, i.e., not
+ coming through port 5404 or 5405
+* TCP traffic to port 43
+* UDP traffic to ports 135 and 445
+* UDP traffic to the port range 137 to 139
+* UDP traffic form source port 137 to port range 1024 to 65535
+* UDP traffic to port 1900
+* TCP traffic to port 135, 139 and 445
+* UDP traffic originating from source port 53
+
+The rest of the traffic is dropped or rejected, respectively, and also logged.
+This may vary depending on the additional options enabled in
+*Firewall* -> *Options*, such as NDP, SMURFS and TCP flag filtering.
+
+[[pve_firewall_iptables_inspect]]
+Please inspect the output of the
+
+----
+ # iptables-save
+----
+
+system command to see the firewall chains and rules active on your system.
+This output is also included in a `System Report`, accessible over a node's
+subscription tab in the web GUI, or through the `pvereport` command line tool.
+
+VM/CT incoming/outgoing DROP/REJECT
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This drops or rejects all the traffic to the VMs, with some exceptions for
+DHCP, NDP, Router Advertisement, MAC and IP filtering depending on the set
+configuration. The same rules for dropping/rejecting packets are inherited
+from the datacenter, while the exceptions for accepted incomming/outgoing
+traffic of the host do not apply.
+
+Again, you can use xref:pve_firewall_iptables_inspect[iptables-save (see above)]
+to inspect all rules and chains applied.
+