The geth CLI options suggest that per default the client listens on TCP port 30303. This page, additionally suggests that UDP port 30301 is used for node discovery.
Is this all that is required or are there any additional ports in use?
[Ethereum] Which TCP and UDP ports are required to run an Ethereum client
firewallsNetworkport-numbers
Related Solutions
You can tell parity to avoid scanning private IPs by simply running:
parity --allow-ips public
You can even fine-tune parity to do less aggressive peering:
parity --allow-ips public --no-discovery --max-pending-peers 4 --min-peers 4 --max-peers 8
Or just block reserved IPs via iptables:
iptables -A OUTPUT -p tcp -s 0/0 -d 0.0.0.0/8 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 100.64.0.0/10 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 169.254.0.0/16 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 192.0.0.0/24 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 192.0.2.0/24 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 192.88.99.0/24 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 198.18.0.0/15 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 198.51.100.0/24 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 203.0.113.0/24 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 224.0.0.0/4 -j DROP
iptables -A OUTPUT -p tcp -s 0/0 -d 240.0.0.0/4 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 0.0.0.0/8 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 100.64.0.0/10 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 169.254.0.0/16 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 192.0.0.0/24 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 192.0.2.0/24 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 192.88.99.0/24 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 198.18.0.0/15 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 198.51.100.0/24 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 203.0.113.0/24 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 224.0.0.0/4 -j DROP
iptables -A OUTPUT -p udp -s 0/0 -d 240.0.0.0/4 -j DROP
Only a partial answer for the first couple of sub-questions...
How many nodes do we connect to?
The maximum number is set to 25 by default, but can be configured using the --maxpeers flag on the command line. This limit is flexible when taking into account "trusted" nodes. (See below.)
The finer detail is that we can also set the combined total of both pending incoming and outgoing connections using the --maxpendpeers flag. This is the number of nodes simultaneously performing connection handshakes, which may or may not be successful, and which depends on whether we can verify their identity. This is set to 66 by default (50 and 16 respectively).
What is the criteria for selecting which nodes to connect to?
There are three different categories of nodes that we connect to, though I'm unsure of the criteria they must meet (other than they must complete the handshake process):
Bootstrap nodes
// Bootstrap nodes are used to establish connectivity // with the rest of the network. BootstrapNodes []*discover.NodeStatic nodes:
// Static nodes are used as pre-configured connections which are always // maintained and re-connected on disconnects. StaticNodes []*discover.NodeTrusted nodes:
// Trusted nodes are used as pre-configured connections which are always // allowed to connect, even above the peer limit. TrustedNodes []*discover.Node
admin.addPeer() allows you to add a new entry to the array of static nodes.
Best Answer
Ethereum clients use a listener (TCP) port and a discovery (UDP) port, both on 30303 by default.
If you need to run JSON-RPC, you'll also need TCP port 8545. Note that JSON-RPC port should not be opened to the outside world, because from there you can do admin operations.
All client's ports can be customized from the default.
If you want geth/eth to find UPnP, you'll also want that enabled on your router. That's just so it can listen on a port, not necessary if you've already manually opened/routed them.
About the wiki page you linked, it reports actually just an example:
I think this misunderstanding is spreading also because of the behavior of the bootnode util. In fact, it uses 30301 as default UDP discovery port.
Note: geth will use IPv6 as a priority if it is available which may cause problems if you assume it is listening to the IPv4 address.