diff --git a/node/Constants.hpp b/node/Constants.hpp
index 5021724fd..4d720d5d9 100644
--- a/node/Constants.hpp
+++ b/node/Constants.hpp
@@ -133,7 +133,7 @@ error_no_byte_order_defined;
 #define ZT_UDP_DEFAULT_PAYLOAD_MTU 1444
 
 /**
- * MTU used for Ethernet tap device
+ * Default MTU used for Ethernet tap device
  *
  * This is pretty much an unchangeable global constant. To make it change
  * across nodes would require logic to send ICMP packet too big messages,
diff --git a/node/MAC.hpp b/node/MAC.hpp
index 634f90339..cd749911d 100644
--- a/node/MAC.hpp
+++ b/node/MAC.hpp
@@ -224,7 +224,7 @@ public:
 		throw()
 	{
 		unsigned char a = ((unsigned char)(nwid & 0xfe) | 0x02); // locally administered, not multicast, from LSB of network ID
-		return ((a == 0x52) ? 0x32 : a); // blacklist 0x52 since it's used by KVM
+		return ((a == 0x52) ? 0x32 : a); // blacklist 0x52 since it's used by KVM, libvirt, and other popular virtualization engines... seems de-facto standard on Linux
 	}
 
 	/**
diff --git a/node/Switch.cpp b/node/Switch.cpp
index 1c2fe8b14..88ad8f5d6 100644
--- a/node/Switch.cpp
+++ b/node/Switch.cpp
@@ -141,6 +141,8 @@ void Switch::onLocalEthernet(const SharedPtr<Network> &network,const MAC &from,c
 			return;
 		}
 
+		TRACE("%s: MULTICAST %s -> %s %s %d",network->tapDeviceName().c_str(),from.toString().c_str(),mg.toString().c_str(),etherTypeName(etherType),(int)data.size());
+
 		const unsigned int mcid = ++_multicastIdCounter & 0xffffff;
 		const uint16_t bloomNonce = (uint16_t)(_r->prng->next32() & 0xffff); // doesn't need to be cryptographically strong
 		unsigned char bloom[ZT_PROTO_VERB_MULTICAST_FRAME_LEN_PROPAGATION_BLOOM];