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 install Windows or other OS and then bring to another computer by using a physical drive and Virtual Machine with QEMU
  • PXE-E23 Error BOOTx64.EFI GRUB booting is 0 bytes tftp pxe dhcp solution NBP filesize is 0 Bytes
  • vagrant install on Debian Mint Ubuntu Linux RHEL Quick Setup Guide Tutorial
  • RHEL 8 CentOS 8, Alma Linux 8, Rocky Linux 8 System Not Booting with RAID or on other servers/computers Solution for dracut and initramfs missing kernel modules
  • How to Upgrade to Debian 11 from Version 8,9,10
  • Ubuntu Linux Mint Debian Redhat Cannot View Files on Android iPhone USB File Transfer Not Working Solution
  • Virtualbox Best Networking Mode In Lab/Work Environment without using NAT Network or Bridged
  • debootstrap how to install Ubuntu, Mint, Debian install
  • Linux grub not using UUID for the root device instead it uses /dev/sda1 or other device name solution
  • How To Restore Partition Table on Running Linux Mint Ubuntu Debian Machine
  • Debian Ubuntu apt install stop daemon questions/accept the default action without prompting
  • iptables NAT how to enable PPTP in newer Debian/Ubuntu/Mint Kernels Linux
  • Grandstream Phone Vulnerability Security Issue Remote Backdoor Connection to 207.246.119.209:3478
  • Linux How to Check Which NIC is Onboard eth0 or eth1 Ubuntu Centos Debian Mint
  • VboxManage VirtualBox NAT Network Issues Managment Troubleshooting
  • Dell PowerEdge Server iDRAC Remote KVM/IP Default Username, Password Reset and Login Information Solution
  • Nvidia Tesla GPUs K40/K80/M40/P40/P100/V100 at home/desktop hacking, cooling, powering, cable solutions Tutorial AIO Solutions
  • Stop ls in Linux Debian Mint CentOS Ubuntu from applying quotes around filenames and directory names
  • Thunderbird Attachment Download Error Corrupt Wrong filesize of 29 or 27 bytes Solution
  • Generic IP Camera LAN Default IP Settings DVR