diff --git a/test/case/firewall/basic/test.py b/test/case/firewall/basic/test.py
index eeb934dc..d25d0b11 100755
--- a/test/case/firewall/basic/test.py
+++ b/test/case/firewall/basic/test.py
@@ -22,10 +22,12 @@ with infamy.Test() as test:
         target = env.attach("target", "mgmt")
         _, data_if = env.ltop.xlate("target", "data")
         _, mgmt_if = env.ltop.xlate("target", "mgmt")
-        _, unused_if = env.ltop.xlate("target", "unused")
         _, host_data = env.ltop.xlate("host", "data")
         TARGET_IP = "192.168.1.1"
         HOST_IP = "192.168.1.42"
+        # A dummy interface stands in for an unused port: it is not placed
+        # in any zone, so it must fall back to the default zone.
+        UNUSED_IF = "dummy0"
 
     with test.step("Configure basic end-device firewall"):
         target.put_config_dicts({
@@ -41,6 +43,11 @@ with infamy.Test() as test:
                                     "prefix-length": 24
                                 }]
                             }
+                        },
+                        {
+                            "name": UNUSED_IF,
+                            "type": "infix-if-type:dummy",
+                            "enabled": True
                         }
                     ]
                 }
@@ -119,16 +126,14 @@ with infamy.Test() as test:
         assert "http" in public_zone["service"]
 
     with test.step("Verify unused interface assigned to default zone"):
-        data = target.get_data("/infix-firewall:firewall")
-        fw = data["firewall"]
+        def unused_in_default_zone():
+            data = target.get_data("/infix-firewall:firewall")
+            fw = data["firewall"]
+            assert fw["default"] == "public-untrusted-net", "Default zone should be 'public-untrusted-net'"
+            zones = {zone["name"]: zone for zone in fw["zone"]}
+            return UNUSED_IF in zones["public-untrusted-net"].get("interface", [])
 
-        assert fw["default"] == "public-untrusted-net", "Default zone should be 'public-untrusted-net'"
-
-        zones = {zone["name"]: zone for zone in fw["zone"]}
-        public_zone = zones["public-untrusted-net"]
-
-        assert unused_if in public_zone["interface"], \
-            f"Unused interface {unused_if} should be in default zone 'public-untrusted-net', got interfaces: {public_zone['interface']}"
+        until(unused_in_default_zone, attempts=10)
 
     with infamy.IsolatedMacVlan(host_data) as ns:
         ns.addip(HOST_IP)
diff --git a/test/case/firewall/basic/topology.dot b/test/case/firewall/basic/topology.dot
index 52174355..84948360 100644
--- a/test/case/firewall/basic/topology.dot
+++ b/test/case/firewall/basic/topology.dot
@@ -1,4 +1,4 @@
-graph "1x3" {
+graph "1x2" {
     layout  = "neato";
     overlap = false;
     esep    = "+30";
@@ -8,23 +8,16 @@ graph "1x3" {
 
     host [
 	  label="host | { <mgmt> mgmt | <data> data }",
-	  pos="10,10.95!",
+	  pos="10,10!",
 	  requires="controller"
     ];
 
     target [
-	    label="{ <mgmt> mgmt | <data> data | <unused> unused } | target",
-	    pos="30,10!",
-	    requires="infix",
-    ];
-
-    dummy [
-	    label="{ <link> link } | dummy",
-	    pos="29.8,00!",
+	    label="{ <mgmt> mgmt | <data> data } | target",
+	    pos="40,10!",
 	    requires="infix",
     ];
 
     host:mgmt -- target:mgmt [requires="mgmt", color="lightgray"]
-    host:data -- target:data [color=black, fontcolor=black, taillabel="192.168.1.42/24"]
-    target:unused -- dummy:link [color="gray", style="dashed"]
+    host:data -- target:data [color=black]
 }
diff --git a/test/case/firewall/basic/topology.svg b/test/case/firewall/basic/topology.svg
index 984e42c5..a65d5300 100644
--- a/test/case/firewall/basic/topology.svg
+++ b/test/case/firewall/basic/topology.svg
@@ -1,58 +1,43 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
-
-<!-- Title: 1x3 Pages: 1 -->
-<svg width="381pt" height="191pt"
- viewBox="0.00 0.00 381.03 190.72" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
-<g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 186.72)">
-<title>1x3</title>
-<polygon fill="white" stroke="transparent" points="-4,4 -4,-186.72 377.03,-186.72 377.03,4 -4,4"/>
+<!-- Generated by graphviz version 2.43.0 (0)
+ -->
+<!-- Title: 1x2 Pages: 1 -->
+<svg width="299pt" height="55pt"
+ viewBox="0.00 0.00 299.02 55.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+<g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 51)">
+<title>1x2</title>
+<polygon fill="white" stroke="transparent" points="-4,4 -4,-51 295.02,-51 295.02,4 -4,4"/>
 <!-- host -->
 <g id="node1" class="node">
 <title>host</title>
-<polygon fill="none" stroke="black" points="0,-136.22 0,-182.22 100,-182.22 100,-136.22 0,-136.22"/>
-<text text-anchor="middle" x="25" y="-155.52" font-family="DejaVu Sans Mono, Book" font-size="14.00">host</text>
-<polyline fill="none" stroke="black" points="50,-136.22 50,-182.22 "/>
-<text text-anchor="middle" x="75" y="-167.02" font-family="DejaVu Sans Mono, Book" font-size="14.00">mgmt</text>
-<polyline fill="none" stroke="black" points="50,-159.22 100,-159.22 "/>
-<text text-anchor="middle" x="75" y="-144.02" font-family="DejaVu Sans Mono, Book" font-size="14.00">data</text>
+<polygon fill="none" stroke="black" points="0,-0.5 0,-46.5 100,-46.5 100,-0.5 0,-0.5"/>
+<text text-anchor="middle" x="25" y="-19.8" font-family="DejaVu Sans Mono, Book" font-size="14.00">host</text>
+<polyline fill="none" stroke="black" points="50,-0.5 50,-46.5 "/>
+<text text-anchor="middle" x="75" y="-31.3" font-family="DejaVu Sans Mono, Book" font-size="14.00">mgmt</text>
+<polyline fill="none" stroke="black" points="50,-23.5 100,-23.5 "/>
+<text text-anchor="middle" x="75" y="-8.3" font-family="DejaVu Sans Mono, Book" font-size="14.00">data</text>
 </g>
 <!-- target -->
 <g id="node2" class="node">
 <title>target</title>
-<polygon fill="none" stroke="black" points="241.03,-112.51 241.03,-181.51 373.03,-181.51 373.03,-112.51 241.03,-112.51"/>
-<text text-anchor="middle" x="274.03" y="-166.31" font-family="DejaVu Sans Mono, Book" font-size="14.00">mgmt</text>
-<polyline fill="none" stroke="black" points="241.03,-158.51 307.03,-158.51 "/>
-<text text-anchor="middle" x="274.03" y="-143.31" font-family="DejaVu Sans Mono, Book" font-size="14.00">data</text>
-<polyline fill="none" stroke="black" points="241.03,-135.51 307.03,-135.51 "/>
-<text text-anchor="middle" x="274.03" y="-120.31" font-family="DejaVu Sans Mono, Book" font-size="14.00">unused</text>
-<polyline fill="none" stroke="black" points="307.03,-112.51 307.03,-181.51 "/>
-<text text-anchor="middle" x="340.03" y="-143.31" font-family="DejaVu Sans Mono, Book" font-size="14.00">target</text>
+<polygon fill="none" stroke="black" points="175.02,-0.5 175.02,-46.5 291.02,-46.5 291.02,-0.5 175.02,-0.5"/>
+<text text-anchor="middle" x="200.02" y="-31.3" font-family="DejaVu Sans Mono, Book" font-size="14.00">mgmt</text>
+<polyline fill="none" stroke="black" points="175.02,-23.5 225.02,-23.5 "/>
+<text text-anchor="middle" x="200.02" y="-8.3" font-family="DejaVu Sans Mono, Book" font-size="14.00">data</text>
+<polyline fill="none" stroke="black" points="225.02,-0.5 225.02,-46.5 "/>
+<text text-anchor="middle" x="258.02" y="-19.8" font-family="DejaVu Sans Mono, Book" font-size="14.00">target</text>
 </g>
 <!-- host&#45;&#45;target -->
 <g id="edge1" class="edge">
 <title>host:mgmt&#45;&#45;target:mgmt</title>
-<path fill="none" stroke="lightgray" stroke-width="2" d="M100,-171.22C100,-171.22 241.03,-170.01 241.03,-170.01"/>
+<path fill="none" stroke="lightgray" stroke-width="2" d="M100,-35.5C100,-35.5 175.02,-35.5 175.02,-35.5"/>
 </g>
 <!-- host&#45;&#45;target -->
 <g id="edge2" class="edge">
 <title>host:data&#45;&#45;target:data</title>
-<path fill="none" stroke="black" stroke-width="2" d="M100,-147.22C100,-147.22 241.03,-147.01 241.03,-147.01"/>
-<text text-anchor="middle" x="159" y="-151.02" font-family="DejaVu Serif, Book" font-size="14.00">192.168.1.42/24</text>
-</g>
-<!-- dummy -->
-<g id="node3" class="node">
-<title>dummy</title>
-<polygon fill="none" stroke="black" points="250.46,-0.5 250.46,-36.5 358.46,-36.5 358.46,-0.5 250.46,-0.5"/>
-<text text-anchor="middle" x="275.46" y="-14.8" font-family="DejaVu Sans Mono, Book" font-size="14.00">link</text>
-<polyline fill="none" stroke="black" points="300.46,-0.5 300.46,-36.5 "/>
-<text text-anchor="middle" x="329.46" y="-14.8" font-family="DejaVu Sans Mono, Book" font-size="14.00">dummy</text>
-</g>
-<!-- target&#45;&#45;dummy -->
-<g id="edge3" class="edge">
-<title>target:unused&#45;&#45;dummy:link</title>
-<path fill="none" stroke="gray" stroke-width="2" stroke-dasharray="5,2" d="M274.03,-112.01C274.03,-112.01 275.46,-36.5 275.46,-36.5"/>
+<path fill="none" stroke="black" stroke-width="2" d="M100,-11.5C100,-11.5 175.02,-11.5 175.02,-11.5"/>
 </g>
 </g>
 </svg>