check for ipv6 address using netaddr.valid_ipv6

daemon/core/nodes/netclient.py

@@ -3,6 +3,7 @@ Clients for dealing with bridge/interface commands.
 """
 import json
 from typing import Callable
+import netaddr
 
 from core.constants import ETHTOOL_BIN, IP_BIN, OVS_BIN, SYSCTL_BIN, TC_BIN
 
@@ -168,7 +169,7 @@ class LinuxNetClient:
             )
         else:
             self.run(f"{IP_BIN} address add {address} dev {device}")
-        if ":" in address:
+        if netaddr.valid_ipv6(address.split("/")[0]):
             # IPv6 addresses are removed by default on interface down.
             # Make sure that the IPv6 address we add is not removed
             self.run(f"{SYSCTL_BIN} -w net.ipv6.conf.{device}.keep_addr_on_down=1")