diff --git a/packages/SwingSet/src/vats/network/network.js b/packages/SwingSet/src/vats/network/network.js
index d3549039bec..d999a2ef733 100644
--- a/packages/SwingSet/src/vats/network/network.js
+++ b/packages/SwingSet/src/vats/network/network.js
@@ -71,7 +71,7 @@ export const ENDPOINT_SEPARATOR = '/';
 
 /**
  * @typedef {Object} ConnectionHandler A handler for a given Connection
- * @property {(connection: Connection, c: ConnectionHandler) => void} [onOpen] The connection has been opened
+ * @property {(connection: Connection, localAddr: Endpoint, remoteAddr: Endpoint, c: ConnectionHandler) => void} [onOpen] The connection has been opened
  * @property {(connection: Connection, packetBytes: Bytes, c: ConnectionHandler) => Promise<Data>} [onReceive] The connection received a packet
  * @property {(connection: Connection, reason?: CloseReason, c: ConnectionHandler) => Promise<void>} [onClose] The connection has been closed
  *
@@ -185,7 +185,7 @@ export const makeConnection = (
 
   current.add(connection);
   E(handler)
-    .onOpen(connection, handler)
+    .onOpen(connection, localAddr, remoteAddr, handler)
     .catch(rethrowUnlessMissing);
   return connection;
 };
@@ -257,15 +257,19 @@ export function crossoverConnection(
   makeHalfConnection(0, 1);
   makeHalfConnection(1, 0);
 
-  function openHalfConnection(l) {
+  /**
+   * @param {number} l local side of the connection
+   * @param {number} r remote side of the connection
+   */
+  function openHalfConnection(l, r) {
     current.add(conns[l]);
     E(handlers[l])
-      .onOpen(conns[l], handlers[l])
+      .onOpen(conns[l], addrs[l], addrs[r], handlers[l])
       .catch(rethrowUnlessMissing);
   }
 
-  openHalfConnection(0);
-  openHalfConnection(1);
+  openHalfConnection(0, 1);
+  openHalfConnection(1, 0);
 
   const [conn0, conn1] = conns;
   return [conn0, conn1];
diff --git a/packages/SwingSet/test/test-network.js b/packages/SwingSet/test/test-network.js
index fbc10ff08af..093cf0f74ed 100644
--- a/packages/SwingSet/test/test-network.js
+++ b/packages/SwingSet/test/test-network.js
@@ -86,7 +86,7 @@ test('handled protocol', async t => {
     await port.connect(
       '/ibc/*/ordered/echo',
       harden({
-        async onOpen(connection) {
+        async onOpen(connection, _localAddr, _remoteAddr) {
           const ack = await connection.send('ping');
           // log(ack);
           t.equals(`${ack}`, 'ping', 'received pong');
@@ -138,7 +138,7 @@ test('protocol connection listen', async t => {
         );
         let handler;
         return harden({
-          async onOpen(connection, connectionHandler) {
+          async onOpen(connection, _localAddr, _remoteAddr, connectionHandler) {
             t.assert(
               connectionHandler,
               `connectionHandler is tracked in onOpen`,
@@ -198,9 +198,14 @@ test('protocol connection listen', async t => {
       '/net/ordered/ordered/some-portname',
       harden({
         ...connectionHandler,
-        async onOpen(connection, c) {
+        async onOpen(connection, localAddr, remoteAddr, c) {
           if (connectionHandler.onOpen) {
-            await connectionHandler.onOpen(connection, c);
+            await connectionHandler.onOpen(
+              connection,
+              localAddr,
+              remoteAddr,
+              c,
+            );
           }
           connection.send('ping');
         },
@@ -245,7 +250,7 @@ test('loopback protocol', async t => {
     await port2.connect(
       port.getLocalAddress(),
       harden({
-        async onOpen(c, _connectionHandler) {
+        async onOpen(c, _localAddr, _remoteAddr, _connectionHandler) {
           t.equals(`${await c.send('ping')}`, 'pingack', 'expected pingack');
           closed.resolve();
         },
diff --git a/packages/cosmic-swingset/lib/ag-solo/vats/ibc.js b/packages/cosmic-swingset/lib/ag-solo/vats/ibc.js
index 12a18d2add0..954d4d386df 100644
--- a/packages/cosmic-swingset/lib/ag-solo/vats/ibc.js
+++ b/packages/cosmic-swingset/lib/ag-solo/vats/ibc.js
@@ -223,8 +223,14 @@ export function makeIBCProtocolHandler(
     }
 
     return harden({
-      async onOpen(conn, _handler) {
-        console.info('onOpen Remote IBC Connection', channelID, portID);
+      async onOpen(conn, localAddr, remoteAddr, _handler) {
+        console.info(
+          'onOpen Remote IBC Connection',
+          channelID,
+          portID,
+          localAddr,
+          remoteAddr,
+        );
         const connP = /** @type {Promise<Connection, any>} */ (E.when(conn));
         channelKeyToConnP.init(channelKey, connP);
       },