diff --git a/app/pages/project/instances/instance/tabs/NetworkingTab.tsx b/app/pages/project/instances/instance/tabs/NetworkingTab.tsx
index 1315fcd6f7..5982230e21 100644
--- a/app/pages/project/instances/instance/tabs/NetworkingTab.tsx
+++ b/app/pages/project/instances/instance/tabs/NetworkingTab.tsx
@@ -19,7 +19,7 @@ import {
   type ExternalIp,
   type InstanceNetworkInterface,
 } from '@oxide/api'
-import { Networking24Icon } from '@oxide/design-system/icons/react'
+import { IpGlobal24Icon, Networking24Icon } from '@oxide/design-system/icons/react'
 
 import { HL } from '~/components/HL'
 import { CreateNetworkInterfaceForm } from '~/forms/network-interface-create'
@@ -255,6 +255,16 @@ export function NetworkingTab() {
     }),
   ]
 
+  const ephemeralIpDetach = useApiMutation('instanceEphemeralIpDetach', {
+    onSuccess() {
+      queryClient.invalidateQueries('instanceExternalIpList')
+      addToast({ content: 'Your ephemeral IP has been detached' })
+    },
+    onError: (err) => {
+      addToast({ title: 'Error', content: err.message, variant: 'error' })
+    },
+  })
+
   const floatingIpDetach = useApiMutation('floatingIpDetach', {
     onSuccess() {
       queryClient.invalidateQueries('floatingIpList')
@@ -275,35 +285,50 @@ export function NetworkingTab() {
         },
       }
 
-      if (externalIp.kind === 'floating') {
-        return [
-          copyAction,
-          {
-            label: 'Detach',
-            onActivate: () =>
-              confirmAction({
-                actionType: 'danger',
-                doAction: () =>
-                  floatingIpDetach.mutateAsync({
-                    path: { floatingIp: externalIp.name },
-                    query: { project },
-                  }),
-                modalTitle: 'Detach Floating IP',
-                modalContent: (
-                  <p>
-                    Are you sure you want to detach floating IP <HL>{externalIp.name}</HL>{' '}
-                    from <HL>{instanceName}</HL>? The instance will no longer be reachable
-                    at <HL>{externalIp.ip}</HL>.
-                  </p>
-                ),
-                errorTitle: 'Error detaching floating IP',
-              }),
-          },
-        ]
-      }
+      const doAction =
+        externalIp.kind === 'floating'
+          ? () =>
+              floatingIpDetach.mutateAsync({
+                path: { floatingIp: externalIp.name },
+                query: { project },
+              })
+          : () =>
+              ephemeralIpDetach.mutateAsync({
+                path: { instance: instanceName },
+                query: { project },
+              })
+
+      return [
+        copyAction,
+        {
+          label: 'Detach',
+          onActivate: () =>
+            confirmAction({
+              actionType: 'danger',
+              doAction,
+              modalTitle: `Confirm detach ${externalIp.kind} IP`,
+              modalContent: (
+                <p>
+                  Are you sure you want to detach{' '}
+                  {externalIp.kind === 'ephemeral' ? (
+                    'this ephemeral IP'
+                  ) : (
+                    <>
+                      floating IP <HL>{externalIp.name}</HL>
+                    </>
+                  )}{' '}
+                  from <HL>{instanceName}</HL>? The instance will no longer be reachable at{' '}
+                  <HL>{externalIp.ip}</HL>.
+                </p>
+              ),
+              errorTitle: `Error detaching ${externalIp.kind} IP`,
+            }),
+        },
+      ]
+
       return [copyAction]
     },
-    [floatingIpDetach, instanceName, project]
+    [ephemeralIpDetach, floatingIpDetach, instanceName, project]
   )
 
   const ipTableInstance = useReactTable({
@@ -338,7 +363,17 @@ export function NetworkingTab() {
           />
         )}
       </TableControls>
-      <Table aria-labelledby="attached-ips-label" table={ipTableInstance} />
+      {eips.items.length > 0 ? (
+        <Table aria-labelledby="attached-ips-label" table={ipTableInstance} />
+      ) : (
+        <TableEmptyBox>
+          <EmptyMessage
+            icon={<IpGlobal24Icon />}
+            title="No external IPs"
+            body="You need to attach an external IP to be able to see it here"
+          />
+        </TableEmptyBox>
+      )}
 
       <TableControls className="mt-8">
         <TableTitle id="nics-label">Network interfaces</TableTitle>
diff --git a/mock-api/msw/handlers.ts b/mock-api/msw/handlers.ts
index 28736e37c6..ef04401c2a 100644
--- a/mock-api/msw/handlers.ts
+++ b/mock-api/msw/handlers.ts
@@ -561,6 +561,16 @@ export const handlers = makeHandlers({
     disk.state = { state: 'detached' }
     return disk
   },
+  instanceEphemeralIpDetach({ path, query }) {
+    const instance = lookup.instance({ ...path, ...query })
+    // match API logic: find/remove first ephemeral ip attached to instance
+    // https://github.com/oxidecomputer/omicron/blob/d52aad0/nexus/db-queries/src/db/datastore/external_ip.rs#L782-L794
+    // https://github.com/oxidecomputer/omicron/blob/d52aad0/nexus/src/app/sagas/instance_ip_detach.rs#L79-L82
+    const ip = db.ephemeralIps.find((eip) => eip.instance_id === instance.id)
+    if (!ip) throw notFoundErr(`ephemeral IP for instance ${instance.name}`)
+    db.ephemeralIps = db.ephemeralIps.filter((eip) => eip !== ip)
+    return 204
+  },
   instanceExternalIpList({ path, query }) {
     const instance = lookup.instance({ ...path, ...query })
 
@@ -1281,7 +1291,6 @@ export const handlers = makeHandlers({
   certificateDelete: NotImplemented,
   certificateList: NotImplemented,
   certificateView: NotImplemented,
-  instanceEphemeralIpDetach: NotImplemented,
   instanceEphemeralIpAttach: NotImplemented,
   instanceMigrate: NotImplemented,
   instanceSerialConsoleStream: NotImplemented,
diff --git a/test/e2e/instance-networking.e2e.ts b/test/e2e/instance-networking.e2e.ts
index 11e9695ef0..6584b1fbef 100644
--- a/test/e2e/instance-networking.e2e.ts
+++ b/test/e2e/instance-networking.e2e.ts
@@ -87,13 +87,14 @@ test('Instance networking tab — NIC table', async ({ page }) => {
 test('Instance networking tab — External IPs', async ({ page }) => {
   await page.goto('/projects/mock-project/instances/db1/network-interfaces')
   const externalIpTable = page.getByRole('table', { name: 'External IPs' })
+  const attachFloatingIpButton = page.getByRole('button', { name: 'Attach floating IP' })
 
   // See list of external IPs
   await expectRowVisible(externalIpTable, { ip: '123.4.56.0', Kind: 'ephemeral' })
   await expectRowVisible(externalIpTable, { ip: '123.4.56.5', Kind: 'floating' })
 
   // Attach a new external IP
-  await page.click('role=button[name="Attach floating IP"]')
+  await attachFloatingIpButton.click()
   await expectVisible(page, ['role=heading[name="Attach floating IP"]'])
 
   // Select the 'rootbeer-float' option
@@ -111,15 +112,21 @@ test('Instance networking tab — External IPs', async ({ page }) => {
   await expectRowVisible(externalIpTable, { name: 'rootbeer-float' })
 
   // Verify that the "Attach floating IP" button is disabled, since there shouldn't be any more IPs to attach
-  await expect(page.getByRole('button', { name: 'Attach floating IP' })).toBeDisabled()
+  await expect(attachFloatingIpButton).toBeDisabled()
 
   // Detach one of the external IPs
   await clickRowAction(page, 'cola-float', 'Detach')
   await page.getByRole('button', { name: 'Confirm' }).click()
 
-  // Since we detached it, we don't expect to see db1 any longer
+  // Since we detached it, we don't expect to see the row any longer
   await expect(externalIpTable.getByRole('cell', { name: 'cola-float' })).toBeHidden()
 
   // And that button shouldbe enabled again
-  await expect(page.getByRole('button', { name: 'Attach floating IP' })).toBeEnabled()
+  await expect(attachFloatingIpButton).toBeEnabled()
+
+  // Detach the ephemeral IP
+  await expect(externalIpTable.getByRole('cell', { name: 'ephemeral' })).toBeVisible()
+  await clickRowAction(page, 'ephemeral', 'Detach')
+  await page.getByRole('button', { name: 'Confirm' }).click()
+  await expect(externalIpTable.getByRole('cell', { name: 'ephemeral' })).toBeHidden()
 })