Connecting to Isambard


You will need an SSH key-pair to access Isambard.


The following stanza is required in your local ~/.ssh/config in order to traverse the bastion hosts transparently and enable SCP usage:

# --- GW4 Isambard --- #
Host * *isambard
  ForwardAgent yes
  ForwardX11 yes
  ServerAliveInterval 60
  IdentityFile ~/.ssh/id_rsa

# Isambard: MACS
Host login-01.isambard login.isambard
  Hostname login-01
  ProxyCommand ssh 'nc %h %p'

Host login-02.isambard
  Hostname login-02
  ProxyCommand ssh 'nc %h %p'

# Isambard: XCI
Host xcil00.isambard xci.isambard
  Hostname xcil00
  ProxyCommand ssh 'nc %h %p'

Host xcil01.isambard
  Hostname xcil01
  ProxyCommand ssh 'nc %h %p'

# Isambard: A64FX
Host a64fxlogin00.isambard a64fx.isambard
  Hostname gw4a64fxlogin00
  ProxyCommand ssh 'nc %h %p'

Host a64fxlogin01.isambard
  Hostname gw4a64fxlogin01
  ProxyCommand ssh 'nc %h %p'

# Isambard: Phase-3
Host p3login01.isambard p3login.isambard
  Hostname p3login01
  ProxyCommand ssh 'nc %h %p'


Update the ~/.ssh/config with your details:-

  • Substitute XX-USERNAME with your Isambard username

  • The IdentityFile points to the SSH key (private) that will be used for connecting to Isambard, the default for most users will be ~/.ssh/id_rsa. If you are using a different key Eg. ~/keystore/isambard, the entry should be IdentityFile ~/keystore/isambard

  • We recommend you overwrite previous versions of this configuration when updating in to ensure your configuration matches the documentation

To test the connection please first try connecting to the MACS system. This will ensure any initial configuration is performed for the first-time user.

MACS - Multi-Architecture Comparison System

To access the MACS, run either ssh login-XX.isambard or ssh login.isambard

XCI - Marvell Thunder X2

To access the XCI XC50 Arm system, run either ssh xcil00.isambard or ssh xci.isambard

A64FX - Fujitsu A64FX

To access the Fujitsu A64FX Arm system, run either ssh a64fxlogin00.isambard or ssh a64fx.isambard

Phase-3 - GPUs and Milan

To access the Phase-3 system, run either ssh p3login01.isambard or ssh p3login.isambard

Remember to replace XX-USERNAME with your Isambard username.


SSH keys can be created with Puttygen and managed with Putty’s Pageant to make them available to Putty and WinSCP. Especially useful if you use a passphrase to protect your SSH private key.

If you are using windows then the simplest way to set up access to Isambard is to with WinSCP:

  1. First create a New Site

    • Enter Hostname and your Username

    • Note that for Phase 2 (xcil00/01) the names are ‘ex’, ‘see’, ‘eye’, ‘el’, ‘zero’, ‘zero’/’one’.

    • For Phase 1 replace this with login-01/02 as per the ssh config above.

  1. Next click on Advanced and Connection -> Tunnel.

    • Select to ‘Connect through SSH tunnel’

    • Enter the proxy hostname ‘’ and your username.

  1. Click OK and Save, then Login and Enjoy …

Putty provides a shell to a remote server. As in the instructions for Linux a proxy command will be used to access the login node of the system you want.

  1. Set hostname to the the login node of the Isambard system, such as xcil00

  1. Next click on Connection -> Data and add your username to ‘Auto-login username’ e.g. xx-myname

  1. Next click on Connection -> Proxy

    • Select ‘Local’ for ‘Proxy type’

    • Enter ‘’ for ‘Proxy hostname’

    • Enter your username for ‘Username’

    • Enter ‘plink %proxyhost -l %user -agent -nc %host:%port’ for ‘Telnet command, or local proxy command’

    • Make sure Pageant is used when using the above command since plink needs to use the ssh key information.

  1. Click back to Session and save your connection settings and connect. If using ssh keys you should not need to use a password.