Mention firewall requirement for Layer 2
Fixes
@@ -46,10 +46,10 @@ MetalLB requires the following to function:
[cluster network configuration]({{% relref "installation/network-addons.md" %}}) that
can coexist with MetalLB.
- Some IPv4 addresses for MetalLB to hand out.
-- Depending on the operating mode, you may need one or more routers
- capable of
- speaking
- [BGP](https://en.wikipedia.org/wiki/Border_Gateway_Protocol).
+- When using the BGP operating mode, you will need one or more routers
+ capable of speaking [BGP](https://en.wikipedia.org/wiki/Border_Gateway_Protocol).
+- Traffic on port 7946 (TCP & UDP) must be allowed between nodes, as required by
+ [memberlist](https://github.com/hashicorp/memberlist).
## Usage
