A link can be a member of at most one bridge. So, if you want to move a link from one bridge instance to another bridge instance, you must first remove the link from the current bridge before adding it to another bridge.
Links that are assigned to the same bridge must have the same MTU value. Although you can change the MTU value on an existing link, the bridge instance goes into maintenance state until you remove or change the assigned links so that the MTU values match before you restart the bridge.
With the support for FMA datalink alert, an FMA alert is raised whenever, an MTU mismatch is detected between the two datalinks. For more information, see How Datalink MTU Mismatch Errors Are Detected in Troubleshooting Network Administration Issues in Oracle Solaris 11.4.
$ dladm add-bridge -l new-link bridge-name
$ dladm add-bridge -l net2 rialto