# Blue Leader

Blue Leaders are able to communicate with the other Blue Leaders within a [Network Group](broken://pages/-LhFryiuCr1rrhVQqHqW) to facilitate the sharing of cached content between peers across subnet boundaries at the local level. The Blue Leader role is automatically assigned to a client per subnet.

A Blue Leader is basically a Red Leader (assigned using the same selection process) but stripped of the ability to download content over the WAN.

This feature requires Port 3703 (UDP) to be open for Multicast communication from Blue Leaders to clients on the local network segment. All leaders communicate with other leaders on ports 3704 and 3705 (UDP). Also check that the Microsoft BranchCache port is reachable and also the Blue Leader BranchCache port, which is typically assigned to the port one above the Microsoft BranchCache port number. 

### When is a Blue Leader elected?

* When no leader on Wi-Fi networks unless specifically its overridden
* When no leader on subnets with < 5 connected clients
  * Instead we activate a Green Leader for them

### Blue Leader and Delivery Optimization

* DO uses DNS Service Discovery
* Both Green and Blue Leaders forward DNS-SD to other networks in the same Segment from StifleR 2.11 and above.
* This binds DO peers together in Network Groups for smaller downloads
* Blue Leaders do not generate V1 Content, only the Red Leaders make these hash calculations.&#x20;


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