diff --git a/easytier-web/frontend-lib/src/components/UrlListInput.vue b/easytier-web/frontend-lib/src/components/UrlListInput.vue
index 8f58c5a7..1b51a094 100644
--- a/easytier-web/frontend-lib/src/components/UrlListInput.vue
+++ b/easytier-web/frontend-lib/src/components/UrlListInput.vue
@@ -11,8 +11,16 @@ const props = defineProps<{
 
 const list = defineModel<string[]>({ required: true })
 
+const fallbackUrl = () => {
+    const defaultProto = Object.keys(props.protos).includes('tcp')
+        ? 'tcp'
+        : (Object.keys(props.protos)[0] ?? 'tcp')
+    const defaultPort = props.protos[defaultProto] ?? 11010
+    return `${defaultProto}://0.0.0.0:${defaultPort}`
+}
+
 const addUrl = () => {
-    list.value.push(props.defaultUrl || 'tcp://0.0.0.0:11010')
+    list.value.push(props.defaultUrl || fallbackUrl())
 }
 
 const removeUrl = (index: number) => {
diff --git a/easytier-web/frontend-lib/tests/url-list-input.spec.ts b/easytier-web/frontend-lib/tests/url-list-input.spec.ts
new file mode 100644
index 00000000..fb5ae8af
--- /dev/null
+++ b/easytier-web/frontend-lib/tests/url-list-input.spec.ts
@@ -0,0 +1,75 @@
+import { mount } from '@vue/test-utils'
+import { describe, expect, it } from 'vitest'
+import { defineComponent, h, nextTick, ref } from 'vue'
+import UrlListInput from '../src/components/UrlListInput.vue'
+
+const ButtonStub = defineComponent({
+  name: 'Button',
+  emits: ['click'],
+  setup(_, { slots, emit }) {
+    return () => h('button', { onClick: (event: MouseEvent) => emit('click', event) }, slots.default?.())
+  },
+})
+
+const UrlInputStub = defineComponent({
+  name: 'UrlInput',
+  setup(_, { slots }) {
+    return () => h('div', slots.actions?.())
+  },
+})
+
+function mountUrlListInput(protos: Record<string, number>, defaultUrl?: string) {
+  const urls = ref<string[]>([])
+  const wrapper = mount(defineComponent({
+    components: { UrlListInput },
+    setup() {
+      return { urls, protos, defaultUrl }
+    },
+    template: `
+      <UrlListInput
+        v-model="urls"
+        :protos="protos"
+        :default-url="defaultUrl"
+        add-label="add_url"
+      />
+    `,
+  }), {
+    global: {
+      stubs: {
+        Button: ButtonStub,
+        UrlInput: UrlInputStub,
+      },
+    },
+  })
+
+  return { wrapper, urls }
+}
+
+describe('UrlListInput.vue add fallback', () => {
+  it('derives the fallback URL from protos when defaultUrl is not provided', async () => {
+    const { wrapper, urls } = mountUrlListInput({ tcp: 11010, udp: 11010 })
+
+    await wrapper.find('.cursor-pointer').trigger('click')
+    await nextTick()
+
+    expect(urls.value).toEqual(['tcp://0.0.0.0:11010'])
+  })
+
+  it('supports port-zero fallback from protos', async () => {
+    const { wrapper, urls } = mountUrlListInput({ tcp: 0, udp: 0 })
+
+    await wrapper.find('.cursor-pointer').trigger('click')
+    await nextTick()
+
+    expect(urls.value).toEqual(['tcp://0.0.0.0:0'])
+  })
+
+  it('uses defaultUrl when provided', async () => {
+    const { wrapper, urls } = mountUrlListInput({ tcp: 11010 }, 'udp://0.0.0.0:22000')
+
+    await wrapper.find('.cursor-pointer').trigger('click')
+    await nextTick()
+
+    expect(urls.value).toEqual(['udp://0.0.0.0:22000'])
+  })
+})