diff --git a/cmd/ctrld/control_client.go b/cmd/ctrld/control_client.go
index 0a94c99..8a41193 100644
--- a/cmd/ctrld/control_client.go
+++ b/cmd/ctrld/control_client.go
@@ -20,7 +20,7 @@ func newControlClient(addr string) *controlClient {
 				return d.DialContext(ctx, "unix", addr)
 			},
 		},
-		Timeout: time.Second * 5,
+		Timeout: time.Second * 30,
 	}}
 }
 
diff --git a/internal/clientinfo/client_info.go b/internal/clientinfo/client_info.go
index 4d6d065..f648ac9 100644
--- a/internal/clientinfo/client_info.go
+++ b/internal/clientinfo/client_info.go
@@ -229,6 +229,14 @@ func (t *Table) lookupHostnameAll(ip, mac string) []*hostnameEntry {
 	var res []*hostnameEntry
 	for _, r := range t.hostnameResolvers {
 		src := r.String()
+		// For ptrDiscover, lookup hostname may block due to server unavailable,
+		// so only lookup from cache to prevent timeout reached.
+		if ptrResolver, ok := r.(*ptrDiscover); ok {
+			if name := ptrResolver.lookupHostnameFromCache(ip); name != "" {
+				res = append(res, &hostnameEntry{name: name, src: src})
+			}
+			continue
+		}
 		if name := r.LookupHostnameByIP(ip); name != "" {
 			res = append(res, &hostnameEntry{name: name, src: src})
 			continue
diff --git a/internal/clientinfo/ptr_lookup.go b/internal/clientinfo/ptr_lookup.go
index 29526fa..ba76b12 100644
--- a/internal/clientinfo/ptr_lookup.go
+++ b/internal/clientinfo/ptr_lookup.go
@@ -40,6 +40,13 @@ func (p *ptrDiscover) String() string {
 	return "ptr"
 }
 
+func (p *ptrDiscover) lookupHostnameFromCache(ip string) string {
+	if val, ok := p.hostname.Load(ip); ok {
+		return val.(string)
+	}
+	return ""
+}
+
 func (p *ptrDiscover) lookupHostname(ip string) string {
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
 	defer cancel()