Hi,
It is designed to accept the both single and multi-value but not range of IP's.
ProxyDefinition
Specifies the IP address of a proxy (such as a cache device) that requires the use of a custom HTTP header. This custom header helps the agent resolve the IP addresses of the requester.
Default: No default
Limits: The string must contain an IP address. Do not use server names or fully qualified DNS host names.
Thanks,
Sharan