Network is unreachable & connection time out

Hello,

I am working on access FABRIC VM slivers using the bastion host from Jupyter Hub, following by https://learn.fabric-testbed.net/knowledge-base/logging-into-fabric-vms/#ssh-keypair-primer-creating-identifying-fingerprinting-keypairs.

I tried to access slivers
ssh -F ~/work/.ssh/fabric-ssh-config -i ~/work/.ssh/sliver_key_pair ubuntu@11.22.33.44
It shows error:
channel 0: open failed: connect failed: connection timed out

In addition, when I tried
ssh -F ~/work/.ssh/fabric-ssh-config centos@1.2.3.4
It shows error:
channel 0: open failed: connect failed: Connection timed out

I’not sure where the problem is. If you could help me with that, I will much appreciate your help.

FYI
cat fabric-ssh-config

UserKnownHostsFile /dev/null
StrictHostKeyChecking no
ServerAliveInterval 120

Host bastion-?.fabric-testbed.net
User xai_0051546236
ForwardAgent yes
Hostname %h
IdentityFile ~/work/.ssh/id_rsa_fabric
IdentitiesOnly yes

Host * !bastion-?.fabric-testbed.net
ProxyJump xai_0051546236@bastion-1.fabric-testbed.net:22
##ProxyJump xai_0051546236@bastion-2.fabric-testbed.net:22

Thanks,
Xusheng