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I installed the latest CentOS 7 version 1611 on a Hyper-V VM with static IP. Network and firewall seem to be set up correctly. Now I am trying to simply log into it remotely from Putty. I get "Connection refused" right away.

As a comparison, I also installed Ubuntu Server separately in the same network with same configuration. I have no problem there.

To troubleshoot, I tried the following 6 things. I am a Linux newbie. I really hope someone can detect something wrong in my outputs below or suggest a new solution.

(1) While being logged into the CentOS VM directly, I watched log with following command before trying to connect with Putty.

tail -f /var/log/messages

However, no messages were registered.

(2) /etc/resolv.conf file has the following content.

# Generated by NetworkManager
nameserver 192.168.1.125
nameserver 75.75.75.75
nameserver 75.75.75.76

The first IP is the IP of DNS server (a Windows 2012 R2 Active Directory Domain Controller with DNS), the last 2 are DNS IPs of ISP. From CentOS VM, pinging to other computers with either IP or fully qualified name works fine. Pinging from other computers into CentOS VM also works using IP or fully qualified name.

(3) curl works fine

curl google.com

Gets me some html data.

(4) Firewall seems to indicate "ssh" is allowed in.

firewall-cmd --list-all

outputs the following (as you can see "ssh" is included in the services)

public (active)
target: default
icmp-block-inversion: no
interfaces: eth0
sources: 
services: dhcpv6-client ssh
ports: 
protocols: 
masquerade: no
forward-ports: 
sourceports: 
icmp-blocks: 
rich rules: 

(5) Status of sshd seems to be up and running

service sshd status

outputs the following.

Redirecting to /bin/systemctl status  sshd.service
● sshd.service - OpenSSH server daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled)
Active: active (running) since Sun 2017-03-26 23:49:44 EDT; 1h 18min ago
 Docs: man:sshd(8)
       man:sshd_config(5)
Process: 959 ExecStart=/usr/sbin/sshd $OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 970 (sshd)
CGroup: /system.slice/sshd.service
       └─970 /usr/sbin/sshd

Mar 26 23:49:44 localhost.localdomain systemd[1]: Starting OpenSSH server daemon...
Mar 26 23:49:44 localhost.localdomain systemd[1]: PID file /var/run/sshd.pid not readable (yet?) after start.
Mar 26 23:49:44 localhost.localdomain sshd[970]: Server listening on 0.0.0.0 port 22.
Mar 26 23:49:44 localhost.localdomain sshd[970]: Server listening on :: port 22.
Mar 26 23:49:44 localhost.localdomain systemd[1]: Started OpenSSH server daemon.

(6) /etc/ssh/sshd_config has the following content

HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
SyslogFacility AUTHPRIV
AuthorizedKeysFile  .ssh/authorized_keys
PasswordAuthentication yes
ChallengeResponseAuthentication no
GSSAPIAuthentication yes
GSSAPICleanupCredentials no
UsePAM yes
X11Forwarding yes
UsePrivilegeSeparation sandbox      # Default for new installations.
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS
Subsystem   sftp    /usr/libexec/openssh/sftp-server

Output of netstat -l

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 0.0.0.0:ssh             0.0.0.0:*               LISTEN     
tcp        0      0 localhost:smtp          0.0.0.0:*               LISTEN     
tcp6       0      0 [::]:ssh                [::]:*                  LISTEN     
tcp6       0      0 localhost:smtp          [::]:*                  LISTEN     
udp        0      0 localhost:323           0.0.0.0:*                          
udp6       0      0 localhost:323           [::]:*                             
raw6       0      0 [::]:ipv6-icmp          [::]:*                  7          
Active UNIX domain sockets (only servers)
Proto RefCnt Flags       Type       State         I-Node   Path
unix  2      [ ACC ]     STREAM     LISTENING     9730     /run/systemd/journal/stdout
unix  2      [ ACC ]     STREAM     LISTENING     16151    /var/run/dbus/system_bus_socket
unix  2      [ ACC ]     STREAM     LISTENING     20503    public/flush
unix  2      [ ACC ]     STREAM     LISTENING     20518    public/showq
unix  2      [ ACC ]     STREAM     LISTENING     20472    public/pickup
unix  2      [ ACC ]     STREAM     LISTENING     20478    public/cleanup
unix  2      [ ACC ]     STREAM     LISTENING     20481    public/qmgr
unix  2      [ ACC ]     STREAM     LISTENING     14233    /run/lvm/lvmetad.socket
unix  2      [ ACC ]     SEQPACKET  LISTENING     14243    /run/udev/control
unix  2      [ ACC ]     STREAM     LISTENING     20500    private/verify
unix  2      [ ACC ]     STREAM     LISTENING     20506    private/proxymap
unix  2      [ ACC ]     STREAM     LISTENING     20509    private/proxywrite
unix  2      [ ACC ]     STREAM     LISTENING     20512    private/smtp
unix  2      [ ACC ]     STREAM     LISTENING     20515    private/relay
unix  2      [ ACC ]     STREAM     LISTENING     20521    private/error
unix  2      [ ACC ]     STREAM     LISTENING     20524    private/retry
unix  2      [ ACC ]     STREAM     LISTENING     20527    private/discard
unix  2      [ ACC ]     STREAM     LISTENING     20530    private/local
unix  2      [ ACC ]     STREAM     LISTENING     20533    private/virtual
unix  2      [ ACC ]     STREAM     LISTENING     20536    private/lmtp
unix  2      [ ACC ]     STREAM     LISTENING     20539    private/anvil
unix  2      [ ACC ]     STREAM     LISTENING     20542    private/scache
unix  2      [ ACC ]     STREAM     LISTENING     14016    /run/systemd/private
unix  2      [ ACC ]     STREAM     LISTENING     20485    private/tlsmgr
unix  2      [ ACC ]     STREAM     LISTENING     20488    private/rewrite
unix  2      [ ACC ]     STREAM     LISTENING     20491    private/bounce
unix  2      [ ACC ]     STREAM     LISTENING     20494    private/defer
unix  2      [ ACC ]     STREAM     LISTENING     20497    private/trace
unix  2      [ ACC ]     STREAM     LISTENING     14044    /run/lvm/lvmpolld.socket
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  • what does netstat -l show you?
    – Jeff W.
    Mar 27, 2017 at 16:54
  • Thanks for responding. Idk how to format this for readability but here is the output of netstat -I. Kernel Interface table Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eth0 1500 8920 0 13 0 518 0 0 0 BMRU lo 65536 72 0 0 0 72 0 0 0 LRU
    – SamDevx
    Mar 28, 2017 at 9:38
  • I included the output of netstat -l above. Thanks.
    – SamDevx
    Mar 28, 2017 at 9:54
  • Also, one thing I noticed was the output of systemd-analyze blame shows 21 seconds on Kdump, 5 seconds on NetworkManager! I don't know the significance of this but that seems to indicate network performance issues, right? The system is very slow indeed with ping or curl or when trying to install packages. Not sure if this is connected to my original issue of SSH not working. I have none of these issues with Ubuntu Server VM configured the same way. Thanks, I could use any help :)
    – SamDevx
    Mar 28, 2017 at 10:05
  • afaik you might want to look in /var/log/secure.log for possible auth /reject reasons. try connecting locally (from your server) via ssh, additionally try with the "remote" ip from the server as well. Possibly this can help you pinpoint the issue (firewall perhaps after all) Mar 28, 2017 at 10:09

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