The Juniper vMX 14.1R11 virtual machine image can be downloaded here.
1\ Import into GNS3 as a QEMU appliance. you can run this device with as little as 512M memory, though 1G+ memory is recommended.
2\ Set the network adapter type as ‘Intel e1000’.
3\ The username and password is root/root123
4\ DO NOT use the em0 and em1 interfaces. You can only use the interfaces start from em2. Juniper has reserved em0 and em1 for other purposes.
5\ Have fun and stay tuned.