diff --git a/p2p/base/p2p_transport_channel.cc b/p2p/base/p2p_transport_channel.cc
index f6a3858a6c..9601ee8e9f 100644
--- a/p2p/base/p2p_transport_channel.cc
+++ b/p2p/base/p2p_transport_channel.cc
@@ -70,40 +70,15 @@ uint32_t GetWeakPingIntervalInFieldTrial() {
   return cricket::WEAK_PING_INTERVAL;
 }
 
-rtc::AdapterType GuessAdapterTypeFromNetworkCost(int network_cost) {
-  // The current network costs have been unchanged since they were added
-  // to webrtc. If they ever were to change we would need to reconsider
-  // this method.
-  switch (network_cost) {
-    case rtc::kNetworkCostMin:
-      return rtc::ADAPTER_TYPE_ETHERNET;
-    case rtc::kNetworkCostLow:
-      return rtc::ADAPTER_TYPE_WIFI;
-    case rtc::kNetworkCostCellular:
-      return rtc::ADAPTER_TYPE_CELLULAR;
-    case rtc::kNetworkCostCellular2G:
-      return rtc::ADAPTER_TYPE_CELLULAR_2G;
-    case rtc::kNetworkCostCellular3G:
-      return rtc::ADAPTER_TYPE_CELLULAR_3G;
-    case rtc::kNetworkCostCellular4G:
-      return rtc::ADAPTER_TYPE_CELLULAR_4G;
-    case rtc::kNetworkCostCellular5G:
-      return rtc::ADAPTER_TYPE_CELLULAR_5G;
-    case rtc::kNetworkCostUnknown:
-      return rtc::ADAPTER_TYPE_UNKNOWN;
-    case rtc::kNetworkCostMax:
-      return rtc::ADAPTER_TYPE_ANY;
-  }
-  return rtc::ADAPTER_TYPE_UNKNOWN;
-}
-
 rtc::RouteEndpoint CreateRouteEndpointFromCandidate(
     bool local,
     const cricket::Candidate& candidate,
     bool uses_turn) {
   auto adapter_type = candidate.network_type();
   if (!local && adapter_type == rtc::ADAPTER_TYPE_UNKNOWN) {
-    adapter_type = GuessAdapterTypeFromNetworkCost(candidate.network_cost());
+    bool vpn;
+    std::tie(adapter_type, vpn) =
+        rtc::Network::GuessAdapterFromNetworkCost(candidate.network_cost());
   }
 
   // TODO(bugs.webrtc.org/9446) : Rewrite if information about remote network
diff --git a/rtc_base/network.cc b/rtc_base/network.cc
index 870f22a3a9..24c1993d0f 100644
--- a/rtc_base/network.cc
+++ b/rtc_base/network.cc
@@ -1168,6 +1168,51 @@ uint16_t Network::GetCost() const {
                                   add_network_cost_to_vpn_);
 }
 
+// This is the inverse of ComputeNetworkCostByType().
+std::pair<rtc::AdapterType, bool /* vpn */>
+Network::GuessAdapterFromNetworkCost(int network_cost) {
+  switch (network_cost) {
+    case kNetworkCostMin:
+      return {rtc::ADAPTER_TYPE_ETHERNET, false};
+    case kNetworkCostMin + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_ETHERNET, true};
+    case kNetworkCostLow:
+      return {rtc::ADAPTER_TYPE_WIFI, false};
+    case kNetworkCostLow + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_WIFI, true};
+    case kNetworkCostCellular:
+      return {rtc::ADAPTER_TYPE_CELLULAR, false};
+    case kNetworkCostCellular + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_CELLULAR, true};
+    case kNetworkCostCellular2G:
+      return {rtc::ADAPTER_TYPE_CELLULAR_2G, false};
+    case kNetworkCostCellular2G + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_CELLULAR_2G, true};
+    case kNetworkCostCellular3G:
+      return {rtc::ADAPTER_TYPE_CELLULAR_3G, false};
+    case kNetworkCostCellular3G + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_CELLULAR_3G, true};
+    case kNetworkCostCellular4G:
+      return {rtc::ADAPTER_TYPE_CELLULAR_4G, false};
+    case kNetworkCostCellular4G + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_CELLULAR_4G, true};
+    case kNetworkCostCellular5G:
+      return {rtc::ADAPTER_TYPE_CELLULAR_5G, false};
+    case kNetworkCostCellular5G + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_CELLULAR_5G, true};
+    case kNetworkCostUnknown:
+      return {rtc::ADAPTER_TYPE_UNKNOWN, false};
+    case kNetworkCostUnknown + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_UNKNOWN, true};
+    case kNetworkCostMax:
+      return {rtc::ADAPTER_TYPE_ANY, false};
+    case kNetworkCostMax + kNetworkCostVpn:
+      return {rtc::ADAPTER_TYPE_ANY, true};
+  }
+  RTC_LOG(LS_VERBOSE) << "Unknown network cost: " << network_cost;
+  return {rtc::ADAPTER_TYPE_UNKNOWN, false};
+}
+
 std::string Network::ToString() const {
   rtc::StringBuilder ss;
   // Print out the first space-terminated token of the network desc, plus
diff --git a/rtc_base/network.h b/rtc_base/network.h
index 0b462bdede..5a64c34cd4 100644
--- a/rtc_base/network.h
+++ b/rtc_base/network.h
@@ -526,6 +526,9 @@ class RTC_EXPORT Network {
     SignalNetworkPreferenceChanged(this);
   }
 
+  static std::pair<rtc::AdapterType, bool /* vpn */>
+  GuessAdapterFromNetworkCost(int network_cost);
+
   // Debugging description of this network
   std::string ToString() const;
 
diff --git a/rtc_base/network_constants.h b/rtc_base/network_constants.h
index 0495afdcc9..578b9710d0 100644
--- a/rtc_base/network_constants.h
+++ b/rtc_base/network_constants.h
@@ -57,6 +57,16 @@ enum AdapterType {
 
 std::string AdapterTypeToString(AdapterType type);
 
+// Useful for testing!
+constexpr AdapterType kAllAdapterTypes[] = {
+    ADAPTER_TYPE_UNKNOWN,     ADAPTER_TYPE_ETHERNET,
+    ADAPTER_TYPE_WIFI,        ADAPTER_TYPE_CELLULAR,
+    ADAPTER_TYPE_VPN,         ADAPTER_TYPE_LOOPBACK,
+    ADAPTER_TYPE_ANY,         ADAPTER_TYPE_CELLULAR_2G,
+    ADAPTER_TYPE_CELLULAR_3G, ADAPTER_TYPE_CELLULAR_4G,
+    ADAPTER_TYPE_CELLULAR_5G,
+};
+
 }  // namespace rtc
 
 #endif  // RTC_BASE_NETWORK_CONSTANTS_H_
diff --git a/rtc_base/network_unittest.cc b/rtc_base/network_unittest.cc
index da2fe96bf6..5635f5d868 100644
--- a/rtc_base/network_unittest.cc
+++ b/rtc_base/network_unittest.cc
@@ -1421,6 +1421,45 @@ TEST_F(NetworkTest, NetworkCostVpn_VpnMoreExpensive) {
   delete net2;
 }
 
+TEST_F(NetworkTest, GuessAdapterFromNetworkCost) {
+  webrtc::test::ScopedFieldTrials field_trials(
+      "WebRTC-AddNetworkCostToVpn/Enabled/"
+      "WebRTC-UseDifferentiatedCellularCosts/Enabled/");
+
+  IPAddress ip1;
+  EXPECT_TRUE(IPFromString("2400:4030:1:2c00:be30:0:0:1", &ip1));
+
+  for (auto type : kAllAdapterTypes) {
+    if (type == rtc::ADAPTER_TYPE_VPN)
+      continue;
+    Network net1("em1", "em1", TruncateIP(ip1, 64), 64);
+    net1.set_type(type);
+    auto [guess, vpn] = Network::GuessAdapterFromNetworkCost(net1.GetCost());
+    EXPECT_FALSE(vpn);
+    if (type == rtc::ADAPTER_TYPE_LOOPBACK) {
+      EXPECT_EQ(guess, rtc::ADAPTER_TYPE_ETHERNET);
+    } else {
+      EXPECT_EQ(type, guess);
+    }
+  }
+
+  // VPN
+  for (auto type : kAllAdapterTypes) {
+    if (type == rtc::ADAPTER_TYPE_VPN)
+      continue;
+    Network net1("em1", "em1", TruncateIP(ip1, 64), 64);
+    net1.set_type(rtc::ADAPTER_TYPE_VPN);
+    net1.set_underlying_type_for_vpn(type);
+    auto [guess, vpn] = Network::GuessAdapterFromNetworkCost(net1.GetCost());
+    EXPECT_TRUE(vpn);
+    if (type == rtc::ADAPTER_TYPE_LOOPBACK) {
+      EXPECT_EQ(guess, rtc::ADAPTER_TYPE_ETHERNET);
+    } else {
+      EXPECT_EQ(type, guess);
+    }
+  }
+}
+
 TEST_F(NetworkTest, VpnList) {
   PhysicalSocketServer socket_server;
   {