Port 8500 Consul · TCP

What runs on port 8500

HashiCorp Consul's HTTP API and UI: service catalogue, health checks, KV store. The DNS interface is on 8600, gossip on 8301/8302, RPC on 8300. Unauthenticated Consul exposes service topology and, with the KV store, often configuration and credentials; enable ACLs and TLS.

Software that uses it: HashiCorp Consul · Nomad (uses 4646) · Fabio, Traefik, consul-template (clients)

Should port 8500 be open?

Private network or VPN only. Nothing good comes from this port being reachable from the internet. Keep it on an internal network, reach it over a VPN or an SSH tunnel, and firewall it from everything that does not need it.

• curl -s http://host:8500/v1/status/leader returns the leader; an empty string means no quorum.

Check port 8500

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :8500'
sudo lsof -i :8500

# from another machine: is it reachable?
nc -zv host 8500
nmap -p 8500 host
curl -v telnet://host:8500      # raw TCP connect test, Ctrl-C to leave

A port that answers from the internet when it should not is the finding; nmap from a machine outside your network (or a VPS) is the honest test, because scans from inside the LAN pass the firewall you are trying to verify.

Allow or block port 8500

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 8500 proto tcp
sudo ufw deny 8500/tcp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 tcp dport 8500 accept
nft add rule inet filter input tcp dport 8500 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 8500 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8500 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=8500 protocol=tcp accept'

Replace 10.0.0.0/8 with the networks that need access. Allowing by source address is the rule that matters; "allow 8500" with no source is just "open".

Related ports

• 8200 Vault

Part of the port number reference. Ports are 16-bit numbers; see also the subnet calculator and the packet decoder, which shows ports inside TCP and UDP headers.

Questions