Comment 6 for bug 1292022

L3 extension check is a bit tricky compared to other neutron extensions because floating IP support also depends on L3 extension.
I am working on this bug as a blueprint hide-router-panel-by-config.

Another reason is that Horizon does not have a way to control enabling/disabling panel/dashboard based on extension list from neutron. Dynamic control mechanism is being implemented as a part of blueprint separate-identity-dash and the mechanism can be used to control Neutron related panels.

> And I also found another extension not tested: agent extension. That extension is used in the admin dashboard to list Neutron agents [2]. If that extension is not supported, Horizon raised a 404 error.

Regarding agent extension, we already check agent extension is enabled based on extension list from Neutron.
Please check NetworkAgentsTab.allowed() and if you have still an issue please file it as a separate bug.