The .CA registry requires that name servers for a .CA domain must have unique IP addresses if the host objects are subordinate of a .CA domain. For instance, the IP address for ns1.nameserver.ca must be different from the IP address for ns2.nameserver.ca. This rule applies to both domain registrations and updates replacing name servers.
Otherwise, the domain won't be delegated and the ModifyDomain command will fail with the following error:
code = 541
description = Invalid attribute value
[fury:ciracode => 8008: Unique IP address required for Host]