I just upgraded my MacBook Air (13-inch, Early 2015) from Sierra to High Sierra 10.13.2. I habitually use Cisco AnyConnect to access my corporate network. I use the macOs built-in ssh client to access servers inside my corporate network.
Since the upgrade I get 'network is down' whenever I try to use ssh over the vpn.
With the Cisco vpn client disconnected I can still ssh to my raspberry pi on my home network.
But with the VPN connected if I try to connect to a work machine I get:
ssh -vvv wspasm03 OpenSSH_7.6p1, LibreSSL 2.6.2 debug1: Reading configuration data /Users/XXX/.ssh/config debug1: /Users/XXX/.ssh/config line 1: Applying options for * debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 48: Applying options for * debug2: ssh_connect_direct: needpriv 0 debug1: Connecting to wspasm03 port 22. ssh: connect to host wspasm03 port 22: Network is down
I tried netcat and it can make a tcp connection to the servers with:
nc wspasm03 22 SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
So this is a very odd problem. It feels like ssh is using a different routing table from everything else.
If I run Wireshark capturing the VPN interface I can see netcat making the connection. If I try with ssh I get the 'network is down' error and no packets are captured.
I noticed that the VPN client creates two IP interfaces, utun0 has only an ipv6 address whereas utun1 has both ipv4 and ipv6 addresses. So I tried
ssh -4 but that didn't help.
This is my ~/.ssh/config:
Host * AddressFamily inet CheckHostIP no
This is /etc/ssh/ssh_config (comment and blank lines omitted):
Host * SendEnv LANG LC_*