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You decide to install the Federation for Jira app only on Jira 1. You need a license for the Federation for Jira app only on Jira 1. Now you can use functionality of Federation for Jira, such as /wiki/spaces/FED/pages/12386528 on a dashboard of Jira 1. This will provide you search results across your whole federation. The results displayed on the dashboard of Jira 1, will include issues from all your 3 Jira instances: Jira 1, Jira 2 and Jira 3.
From the point of view of the Federation for Jira app, Jira 1 is your local Jira instance, while Jira 2 and Jira 3 are remote Jira instances.
However since you have not installed the Federation for Jira app on Jira 2 and Jira 3, you cannot use the the /wiki/spaces/FED/pages/12386528 on a dashboard of those instances.From the point of view of the Federation for Jira app, Jira 1 is your local Jira instance, while Jira 2 and Jira 3 are remote Jira instances.