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Thread: Can't access ubuntu server

  1. #1
    Join Date
    Sep 2020
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    6

    Can't access ubuntu server

    We have web server running on ubuntu 14.04 server. This server randomly blocks access from user PC. I can ping other server on the same network but not this server. As a temporary solution i changed the ip address and it works. The firewall is switched off.
    Is there any way to find out why this server refuse connection.
    Last edited by ozarif2006; September 1st, 2020 at 06:43 AM.

  2. #2
    Join Date
    Nov 2009
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    Hidden!
    Distro
    Kubuntu 18.04 Bionic Beaver

    Re: Can't access ubuntu server

    it's in the logs. auth.log and maybe some others as well.

    check /var/log
    Read the easy to understand, lots of pics Ubuntu manual.
    Do i need antivirus/firewall in linux?
    Full disk backup (newer kernel -> suitable for newer PC): Clonezilla
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  3. #3
    Join Date
    Sep 2020
    Beans
    6

    Re: Can't access ubuntu server

    checked /var/auth.log and can't find.

  4. #4
    Join Date
    Sep 2020
    Beans
    6

    Re: Can't access ubuntu server

    i had another ip blocked by ubuntu server. this time I use the same blocked ip and assigned to another pc2. now pc2 is blocked. I can ping the pc2 from the ubuntu server but now from the pc2.
    I also ran tcpdump on ubuntu and it reply back but still no communication from pc2.

  5. #5
    Join Date
    Nov 2009
    Beans
    Hidden!
    Distro
    Kubuntu 18.04 Bionic Beaver

    Re: Can't access ubuntu server

    so an IP connection is blocked. are you using maybe some fail2ban or similar service that blacklisted the IP indefinitely and is keeping it in jail?
    Read the easy to understand, lots of pics Ubuntu manual.
    Do i need antivirus/firewall in linux?
    Full disk backup (newer kernel -> suitable for newer PC): Clonezilla
    User friendly full disk backup: Rescuezilla

  6. #6
    Join Date
    Nov 2008
    Location
    Metro Boston
    Beans
    15,486
    Distro
    Kubuntu 20.04 Focal Fossa

    Re: Can't access ubuntu server

    Are you sure you don't have an IP conflict on your network with two machines having the same address?

    Your servers do use static IP assignments, right? Never rely on DHCP to assign addresses to servers.
    If you ask for help, do not abandon your request. Please have the courtesy to check for responses and thank the people who helped you.

    Blog · Linode System Administration Guides · Android Apps for Ubuntu Users

  7. #7
    Join Date
    Sep 2020
    Beans
    6

    Re: Can't access ubuntu server

    No we dont use such software unless it bundled with OS.
    Quote Originally Posted by mastablasta View Post
    so an IP connection is blocked. are you using maybe some fail2ban or similar service that blacklisted the IP indefinitely and is keeping it in jail?

  8. #8
    Join Date
    Sep 2020
    Beans
    6

    Re: Can't access ubuntu server

    Initially i suspected duplicate ip. but one i am testing is the only ip address. This PC i can ping from the server but not from PC to server. While doing ping test from the server, i removed the network cable to see if there is another device with same ip but not.


    Quote Originally Posted by SeijiSensei View Post
    Are you sure you don't have an IP conflict on your network with two machines having the same address?

    Your servers do use static IP assignments, right? Never rely on DHCP to assign addresses to servers.

  9. #9
    Join Date
    Nov 2008
    Location
    Metro Boston
    Beans
    15,486
    Distro
    Kubuntu 20.04 Focal Fossa

    Re: Can't access ubuntu server

    Is the server running iptables? Is it blocking ICMP (ping) requests?
    If you ask for help, do not abandon your request. Please have the courtesy to check for responses and thank the people who helped you.

    Blog · Linode System Administration Guides · Android Apps for Ubuntu Users

  10. #10
    Join Date
    Feb 2010
    Location
    Obscurial Springs
    Beans
    14,523
    Distro
    Ubuntu Budgie Development Release

    Re: Can't access ubuntu server

    Support request moved to Server Platforms.
    “Start where you are. Use what you have. Do what you can".

    Ubuntu Documentation Search: Popular Pages
    Ubuntu: Security Basics
    Ubuntu: Flavors

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