SSH Server Slow/Lagged/Delayed Login Response

This is really something the SSH Server developers should consider.  The cause of this annoyance is because of failed DNS lookups on your IP address, which is especially common for many dedicated/col-located servers and also computers on internal NAT/private networks.

The chances are this is the cause of your SSH Slow/Delayed Login problems.

The easy solution to SSH Login Problems

Edit /etc/ssh/sshd_config

Add this line to disable reverse DNS lookups when someone is logging into your SSH Server:

UseDNS no

*Don't forget to restart your SSH daemon for the change to take effect!

It would make sense for this option to be disabled by default, especially considering that someone could have a fake or invalid reverse DNS which makes it impossible to find who was really logged in or trying to login.

The SSH daemon should not initially due any reverse DNS or at least allow the login process to continue and try a few more times during the session to find the reverse DNS if it must.

Another symptom aside from it being slow is if you debug the SSH client and see things freeze here:

debug1: SSH2_MSG_SERVICE_ACCEPT received

The problem will be solved once you apply "UseDNS no" to you sshd_confdig and restart SSH.


Tags:

ssh, server, lagged, delayed, login, responsethis, developers, annoyance, dns, lookups, ip, dedicated, col, located, servers, nat, networks, edit, etc, sshd_config, disable, logging, usedns, restart, daemon, disabled, default, invalid, logged, initially, symptom, debug, _msg_service_accept, quot, sshd_confdig,

Latest Articles

  • How to allow SSH root user access in Linux/Debian/Mint/RHEL/Ubuntu/CentOS
  • Ansible Tutorial - Playbook How To Install From Scratch and Deploy LAMP + Wordpress on Remote Server
  • Ceph Install Errors on Proxmox / How To Fix Solution
  • Proxmox Update Error https://enterprise.proxmox.com/debian/pve bullseye InRelease 401 Unauthorized [IP: 144.217.225.162 443]
  • QEMU/KVM How to Hot-add A Virtual Disk .raw/.qcow2 via QEMU Monitor Commands
  • Proxmox How To Enable Ceph Distributed Storage Cluster with OSD and Pools
  • pulseaudio issue on QEMU/KVM guest VM when microphone is replugged/unplugged pulseaudio: pa_threaded_mainloop_lock failed pulseaudio: Reason: Invalid argument
  • Ubuntu Linux Mint - Volume Control Stopped Working
  • Proxmox Services Won't Start Failed to start The Proxmox VE cluster filesystem. Proxmox VE firewall. PVE Status Daemon. Proxmox VE scheduler. PVE Cluster HA Resource Manager Daemon. PVE Local HA Resource Manager Daemon.
  • Proxmox Guide FAQ / Errors / Howto
  • Virtualbox Vbox Issue Cannot Enable Nested Virtualization Button is Grayed/Greyed Out and Unclickable HowTo Solution
  • Virtualbox VBOX Howto Port Forward To Guests
  • Linux Ubuntu Debian Centos Mint - How To Check if Intel VT-x or AMD-V Hardware Virtualization is Enabled?
  • Linux Howto Zip Multiple Files and Directories
  • Windows Cannot Format USB drive Device Media is Write Protected Error Solution
  • Linux Mint 20 cannot install snapd missing solution
  • Virtualbox VBOX How To Install Guest-Utils/GuestUtils so drag and drop and clipboard works Ubuntu Mint Debian Linux
  • How to install Kubernetes with microk8s and deploy apps on Debian/Mint/Ubuntu Linux
  • vi how to delete everything to the end of the line or the rest of the line from the cursor
  • Cisco Howto Configure Console Port/Terminal/Comm Server with Async Cable Setup