diff --git a/repos/os/src/server/nic_router/nat_rule.cc b/repos/os/src/server/nic_router/nat_rule.cc
index dd05062ba7..1839b8ce22 100644
--- a/repos/os/src/server/nic_router/nat_rule.cc
+++ b/repos/os/src/server/nic_router/nat_rule.cc
@@ -84,9 +84,9 @@ Nat_rule &Nat_rule_tree::find_by_domain(Domain &domain)
 void Nat_rule::print(Output &output) const
 {
 	Genode::print(output, "domain ", _domain,
-	                  " tcp-ports ", _tcp_port_alloc.max(),
-	                  " udp-ports ", _udp_port_alloc.max(),
-	                   " icmp-ids ", _icmp_port_alloc.max());
+	                  " tcp-ports ", _tcp_port_alloc.max_nr_of_ports(),
+	                  " udp-ports ", _udp_port_alloc.max_nr_of_ports(),
+	                   " icmp-ids ", _icmp_port_alloc.max_nr_of_ports());
 }
 
 
diff --git a/repos/os/src/server/nic_router/port_allocator.cc b/repos/os/src/server/nic_router/port_allocator.cc
index 65a9e4e69d..d43b18216f 100644
--- a/repos/os/src/server/nic_router/port_allocator.cc
+++ b/repos/os/src/server/nic_router/port_allocator.cc
@@ -21,8 +21,10 @@ using namespace Net;
 using namespace Genode;
 
 
-bool Net::dynamic_port(Port const port) {
-	return port.value >= Port_allocator::FIRST; }
+bool Net::dynamic_port(Port const port)
+{
+	return port.value >= Port_allocator::FIRST_PORT;
+}
 
 
 /********************
@@ -32,16 +34,16 @@ bool Net::dynamic_port(Port const port) {
 Port Net::Port_allocator::alloc()
 {
 	for (unsigned nr_of_trials { 0 };
-	     nr_of_trials < COUNT;
+	     nr_of_trials < NR_OF_PORTS;
 	     nr_of_trials++) {
 
 		uint16_t const port_offset = _next_port_offset;
-		_next_port_offset = (_next_port_offset + 1) % COUNT;
+		_next_port_offset = (_next_port_offset + 1) % NR_OF_PORTS;
 		try {
-			_alloc.alloc_addr(port_offset);
-			return Port { (uint16_t)(port_offset + FIRST) };
+			_bit_allocator.alloc_addr(port_offset);
+			return Port { (uint16_t)(port_offset + FIRST_PORT) };
 		}
-		catch (Bit_allocator<COUNT>::Range_conflict) { }
+		catch (Bit_allocator<NR_OF_PORTS>::Range_conflict) { }
 	}
 	throw Out_of_indices();
 }
@@ -49,15 +51,19 @@ Port Net::Port_allocator::alloc()
 
 void Net::Port_allocator::alloc(Port const port)
 {
-	try { _alloc.alloc_addr(port.value - FIRST); }
-	catch (Genode::Bit_allocator<COUNT>::Range_conflict) {
-		throw Allocation_conflict(); }
+	try {
+		_bit_allocator.alloc_addr(port.value - FIRST_PORT);
+	}
+	catch (Bit_allocator<NR_OF_PORTS>::Range_conflict) {
+
+		throw Allocation_conflict();
+	}
 }
 
 
 void Port_allocator::free(Port const port)
 {
-	_alloc.free(port.value - FIRST);
+	_bit_allocator.free(port.value - FIRST_PORT);
 }
 
 
@@ -67,40 +73,48 @@ void Port_allocator::free(Port const port)
 
 Port Port_allocator_guard::alloc()
 {
-	if (_used == _max) {
-		throw Out_of_indices(); }
-
-	Port const port = _port_alloc.alloc();
-	_used++;
-	return port;
+	if (_used_nr_of_ports == _max_nr_of_ports) {
+		throw Out_of_indices();
+	}
+	try {
+		Port const port = _port_alloc.alloc();
+		_used_nr_of_ports++;
+		return port;
+	}
+	catch (Port_allocator::Out_of_indices) {
+		throw Out_of_indices();
+	}
 }
 
 
 void Port_allocator_guard::alloc(Port const port)
 {
-	if (_used == _max) {
-		throw Out_of_indices(); }
-
+	if (_used_nr_of_ports == _max_nr_of_ports) {
+		throw Out_of_indices();
+	}
 	_port_alloc.alloc(port);
-	_used++;
+	_used_nr_of_ports++;
 }
 
 
 void Port_allocator_guard::free(Port const port)
 {
 	_port_alloc.free(port);
-	_used = _used ? _used - 1 : 0;
+	_used_nr_of_ports = _used_nr_of_ports ? _used_nr_of_ports - 1 : 0;
 }
 
 
 Port_allocator_guard::Port_allocator_guard(Port_allocator &port_alloc,
-                                           unsigned const  max,
+                                           unsigned const  max_nr_of_ports,
                                            bool     const  verbose)
 :
-	_port_alloc(port_alloc),
-	_max(min(max, static_cast<uint16_t>(Port_allocator::COUNT)))
+	_port_alloc  { port_alloc },
+	_max_nr_of_ports {
+		min(max_nr_of_ports,
+		    static_cast<uint16_t>(Port_allocator::NR_OF_PORTS)) }
 {
-	if (verbose && max > (Port_allocator::COUNT)) {
+	if (verbose &&
+	    max_nr_of_ports > (Port_allocator::NR_OF_PORTS)) {
 
 		warning("number of ports was truncated to capacity of allocator");
 	}
diff --git a/repos/os/src/server/nic_router/port_allocator.h b/repos/os/src/server/nic_router/port_allocator.h
index 73f86658fb..a2b7b65cd0 100644
--- a/repos/os/src/server/nic_router/port_allocator.h
+++ b/repos/os/src/server/nic_router/port_allocator.h
@@ -34,12 +34,12 @@ class Net::Port_allocator
 {
 	public:
 
-		enum { FIRST = 49152, COUNT = 16384 };
+		enum { FIRST_PORT = 49152, NR_OF_PORTS = 16384 };
 
 	private:
 
-		Genode::Bit_allocator<COUNT> _alloc            { };
-		Genode::uint16_t             _next_port_offset { 0 };
+		Genode::Bit_allocator<NR_OF_PORTS> _bit_allocator    { };
+		Genode::uint16_t                   _next_port_offset { 0 };
 
 	public:
 
@@ -59,8 +59,8 @@ class Net::Port_allocator_guard
 	private:
 
 		Port_allocator &_port_alloc;
-		unsigned const  _max;
-		unsigned        _used = 0;
+		unsigned const  _max_nr_of_ports;
+		unsigned        _used_nr_of_ports { 0 };
 
 	public:
 
@@ -73,10 +73,10 @@ class Net::Port_allocator_guard
 		void free(Port const port);
 
 		Port_allocator_guard(Port_allocator &port_alloc,
-		                     unsigned const  max,
+		                     unsigned const  max_nr_of_ports,
 		                     bool     const  verbose);
 
-		unsigned max() const { return _max; }
+		unsigned max_nr_of_ports() const { return _max_nr_of_ports; }
 };
 
 #endif /* _PORT_ALLOCATOR_H_ */