If you create, say, a GRE tunnel between 192.0.2.1 and 203.0.113.1, then try to create another one with the same protocol and endpoints, the commit failure is quite unexpected.
vyos@r1# commit [ interfaces tunnel tun11 ] VyOS had an issue completing a command. ... Traceback (most recent call last): File "/usr/libexec/vyos/conf_mode/interfaces-tunnel.py", line 195, in <module> apply(c) File "/usr/libexec/vyos/conf_mode/interfaces-tunnel.py", line 185, in apply tun = TunnelIf(**tunnel) File "/usr/lib/python3/dist-packages/vyos/ifconfig/tunnel.py", line 109, in __init__ super().__init__(ifname, **kargs) File "/usr/lib/python3/dist-packages/vyos/ifconfig/interface.py", line 318, in __init__ self._create() File "/usr/lib/python3/dist-packages/vyos/ifconfig/tunnel.py", line 134, in _create self._cmd(cmd.format(**self.config)) File "/usr/lib/python3/dist-packages/vyos/ifconfig/control.py", line 52, in _cmd return cmd(command, self.debug) File "/usr/lib/python3/dist-packages/vyos/util.py", line 161, in cmd raise OSError(code, feedback) PermissionError: [Errno 1] failed to run command: ip tunnel add tun11 mode ip6gre local 2001:db8:1::1 remote 2001:db8:1::2 tos inherit ttl 64 encaplimit 4 flowlabel inherit hoplimit 64 tclass inherit returned: exit code: 1 noteworthy: cmd 'ip tunnel add tun11 mode ip6gre local 2001:db8:1::1 remote 2001:db8:1::2 tos inherit ttl 64 encaplimit 4 flowlabel inherit hoplimit 64 tclass inherit' returned (out): returned (err): add tunnel "ip6gre0" failed: No buffer space available [[interfaces tunnel tun11]] failed Commit failed [edit interfaces]
Such configs are certainly invalid, but we need to do something about the error message.