I have a CentOS 7 server in which I opened up ports for SNMP connections.
Even though I can see the ports open here:
[matias@Centos_7_VM ~]$ sudo firewall-cmd --list-all
[sudo] password for matias:
public (active)
target: default
icmp-block-inversion: no
interfaces: ens33
sources:
services: ssh dhcpv6-client
ports: 80/tcp 10050/tcp 50000/tcp 161/tcp 160/tcp
protocols:
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules:
When I try to hit this port from the outside I always get that it's closed. Even nmap agrees on this:
Starting Nmap 7.01 ( https://nmap.org ) at 2018-08-01 14:52 -03
Nmap scan report for Centos_7_VM (192.168.43.216)
Host is up (0.52s latency).
Not shown: 996 filtered ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
161/tcp closed snmp
50000/tcp closed ibm-db2
What else can I do to open these ports? (yes, I reloaded firewalld when I initially opened the ports.)
SNMP is a UDP protocol, not a TCP protocol. So you need to open the UDP port, i.e.
161/udp
.Better yet, just specify the service name and firewalld will take care of it.