Hello all. I’m trying to change the SSH port on an Oracle VM, but I’m getting nowhere and I don’t know where to solve the issue.

I have changed the SSH port:

edit /etc/ssh/sshd_config

Entered the port info:

Port 5522

I restarted the service:

sudo systemctl restart ssh

And made sure that the port is open:

ss -an | grep 5522
tcp   LISTEN 0      128                                                                               0.0.0.0:5522                0.0.0.0:*            
tcp   LISTEN 0      128                                                                                  [::]:5522                   [::]:*

I also allow incoming traffic to 5522:

sudo ufw allow 5522/tcp comment 'Open port ssh tcp port 5522'

AND just to make sure, I allow ‘routed’:

sudo ufw default allow FORWARD

And make sure the FW config is valid:

sudo ufw status verbose
Status: active
Logging: on (medium)
Default: deny (incoming), allow (outgoing), allow (routed)
New profiles: skip

To                         Action      From
--                         ------      ----
22/tcp                     ALLOW IN    Anywhere                   # Open port ssh tcp port 22
5522/tcp                   ALLOW IN    Anywhere                  
22/tcp (v6)                ALLOW IN    Anywhere (v6)              # Open port ssh tcp port 22
5522/tcp (v6)              ALLOW IN    Anywhere (v6)              # Open real ssh tcp port 22

Yet, I cannot connect to this server. Trying to ssh -vvvv -p 5522 [ip-adress] yields this:

OpenSSH_9.0p1 Ubuntu-1ubuntu8.4, OpenSSL 3.0.8 7 Feb 2023
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug2: resolve_canonicalize: hostname 129.x.x.5 is address
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/home/x/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/home/x/.ssh/known_hosts2'
debug3: ssh_connect_direct: entering
debug1: Connecting to 129.x.x.5 [129.x.x.5] port 5522.
debug3: set_sock_tos: set socket 3 IP_TOS 0x10
debug1: connect to address 129.x.x.5 port 5522: No route to host
ssh: connect to host 129.x.x.5 port 5522: No route to host

I can connect just fine when the port is at 22, but as soon as I change it to 5522, i get the ‘no route to host’ error.

I’ve made sure I have rules on Oracle cloud that allows ingress and egress traffic to 0.0.0.0/0 on all protocols, no matter the destination / source.

What am I doing wrong? It feels that this problem is host (server) based rather client based, since I’m getting a routing error. Do I need to configure the routing for that port specifically, and if so how?

PS: Also, connecting to localhost:5522 from the server itself works fine. So the problem is not in the configuration, but likely network related.

EDIT: This issue is solved, solution written on this post: https://lemmy.ml/comment/2787074

  • tetra@feddit.de
    2·
    1 year ago

    Ist that 0.0.0.0/24 CIDR a typo? That suffix should probably be /0.

    Also make sure to actually assign the firewall to your instance’s subnet in the Oracle cloud Interface.

    • krashOP
      2·
      1 year ago

      Correct - that was a typo, I’ve corrected the original post. Not a good idea to write a report when you’re angry and tired… 🤣

      The firewall (Network Security Group in Oracle lingo) is indeed attached to the subnet. I think I’ve solved the issue, will write it in a seperate post and link it to the original post.

  • randombullet@feddit.de
    1·
    1 year ago

    Do you have a firewall between the two devices?

    Can you do a packet capture to make sure that both ends are behaving as expected?

    Can you double check your IPs. I’ve had this issue before by fat fingering

    • krashOP
      1·
      1 year ago

      Correct - that was a typo in this post. The output from sudo ufw status verbose is however correct.

      I think I’ve solved the issue, will write it in a seperate post and link it to the original post.

  • krashOP
    1·
    1 year ago

    So I managed to smash a few buttons randomly again, and get this solved.

    There are a few things to be aware of:

    • Oracle doesn’t like ufw. So I disabled it and uninstalled it. Having ufw installed may result in bad stuff. Link
    • I decided to flush all rules in ip-tables to start on a clean slate: sudo iptables -F
    • While I’m at it, I’ve changed ip-tables to allow ALL. THE. INBOUND. TRAFFIC: sudo iptables -I INPUT -j ACCEPT
    • One last thing, I’ve changed the state of the firewall to go from stateful to stateless, still with no restrictions on the ingress / egress traffic.

    This is, of course, not a recommended setup for a host to be used in production or to have critical data, but it gave me a host in a working state that I can work with.

    Some posts that helped me in this: