diff --git a/pacman/model/resources/iptag_resource.py b/pacman/model/resources/iptag_resource.py
index 72a5d2ead..4e6ea3206 100644
--- a/pacman/model/resources/iptag_resource.py
+++ b/pacman/model/resources/iptag_resource.py
@@ -36,7 +36,7 @@ class IPtagResource(object):
         "_traffic_identifier")
 
     def __init__(
-            self, ip_address: Optional[str], port: Optional[int],
+            self, ip_address: str, port: int,
             strip_sdp: bool, tag: Optional[int] = None,
             traffic_identifier: str = "DEFAULT"):
         """
@@ -60,7 +60,7 @@ def __init__(
         self._traffic_identifier = traffic_identifier
 
     @property
-    def ip_address(self) -> Optional[str]:
+    def ip_address(self) -> str:
         """
         The IP address to assign to the tag.
 
@@ -69,7 +69,7 @@ def ip_address(self) -> Optional[str]:
         return self._ip_address
 
     @property
-    def port(self) -> Optional[int]:
+    def port(self) -> int:
         """
         The port of the tag.
 
diff --git a/pacman/model/tags/tags.py b/pacman/model/tags/tags.py
index 83c11537d..577fdb3f8 100644
--- a/pacman/model/tags/tags.py
+++ b/pacman/model/tags/tags.py
@@ -133,13 +133,12 @@ def add_reverse_ip_tag(
                     "reverse_ip_tag", reverse_ip_tag,
                     "The port has already been assigned on the given board")
 
+        board_address = reverse_ip_tag.board_address
         self._reverse_ip_tags[
-            (reverse_ip_tag.board_address,
-             reverse_ip_tag.tag)] = reverse_ip_tag
+            (board_address, reverse_ip_tag.tag)] = reverse_ip_tag
         self._reverse_ip_tags_by_vertex[vertex].append(reverse_ip_tag)
         if reverse_ip_tag.port is not None:
-            self._ports_assigned.add(
-                (reverse_ip_tag.board_address, reverse_ip_tag.port))
+            self._ports_assigned.add((board_address, reverse_ip_tag.port))
 
     @property
     def ip_tags_vertices(self) -> Iterable[Tuple[IPTag, MachineVertex]]:
diff --git a/pacman/operations/tag_allocator_algorithms/basic_tag_allocator.py b/pacman/operations/tag_allocator_algorithms/basic_tag_allocator.py
index 5120515ff..39a62065a 100644
--- a/pacman/operations/tag_allocator_algorithms/basic_tag_allocator.py
+++ b/pacman/operations/tag_allocator_algorithms/basic_tag_allocator.py
@@ -125,8 +125,10 @@ def __find_free_tag(
 def __create_tag(
         eth_chip: Chip, placement: Placement, iptag: IPtagResource,
         tag: int) -> IPTag:
+    ethernet_ip = eth_chip.ip_address
+    assert ethernet_ip is not None
     return IPTag(
-        eth_chip.ip_address, placement.x, placement.y,
+        ethernet_ip, placement.x, placement.y,
         tag, iptag.ip_address, iptag.port,
         iptag.strip_sdp, iptag.traffic_identifier)
 
@@ -135,8 +137,10 @@ def __create_reverse_tag(
         eth_chip: Chip, placement: Placement,
         reverse_iptag: ReverseIPtagResource, tag: int,
         port: int) -> ReverseIPTag:
+    ethernet_ip_address = eth_chip.ip_address
+    assert ethernet_ip_address is not None
     return ReverseIPTag(
-        eth_chip.ip_address, tag, port, placement.x, placement.y, placement.p,
+        ethernet_ip_address, tag, port, placement.x, placement.y, placement.p,
         reverse_iptag.sdp_port)