diff --git a/src/config/router.rs b/src/config/router.rs
index cfee4f8..9247cc3 100644
--- a/src/config/router.rs
+++ b/src/config/router.rs
@@ -58,11 +58,10 @@ impl Router for RouterConfig {
             .or(self.default.as_ref())
             .ok_or(RouterError::NoServer)?;
 
-        let address: SocketAddr = match route.ip {
-            RouteType::Simple(address) => address.into(),
-            RouteType::Balanced(ref list) => {
-                let hash = client.hash();
-                list.get(hash as usize)
+        let address: SocketAddr = match &route.ip {
+            RouteType::Simple(addr) => addr.resolve().ok_or(RouterError::Unavailable)?,
+            RouteType::Balanced(list) => {
+                list.get(client.hash() as usize).ok_or(RouterError::Unavailable)?
             }
         };
 
diff --git a/src/config/router/balancer.rs b/src/config/router/balancer.rs
index 770a01b..b2e2491 100644
--- a/src/config/router/balancer.rs
+++ b/src/config/router/balancer.rs
@@ -22,7 +22,7 @@ pub struct Balanced {
 // }
 
 impl Balanced {
-    pub(super) fn get(&self, n: usize) -> SocketAddr {
-        self.servers[n & self.servers.len()].into()
+    pub(super) fn get(&self, n: usize) -> Option<SocketAddr> {
+        self.servers[n % self.servers.len()].resolve()
     }
 }
diff --git a/src/config/router/resolver.rs b/src/config/router/resolver.rs
index b66a16a..8fd3b0d 100644
--- a/src/config/router/resolver.rs
+++ b/src/config/router/resolver.rs
@@ -2,26 +2,26 @@ use std::net::{SocketAddr, ToSocketAddrs};
 
 use serde::{Deserialize, Deserializer};
 
-#[derive(Deserialize, Debug, Clone, Copy)]
-pub(super) struct ResolvableAddr(#[serde(deserialize_with = "resolve_hostname")] SocketAddr);
+#[derive(Deserialize, Debug, Clone)]
+pub(super) struct ResolvableAddr(#[serde(deserialize_with = "parse_addr_string")] String);
 
-fn resolve_hostname<'de, D>(deserializer: D) -> Result<SocketAddr, D::Error>
+fn parse_addr_string<'de, D>(deserializer: D) -> Result<String, D::Error>
 where
     D: Deserializer<'de>,
 {
     use serde::de::Error;
 
-    let inner = <String>::deserialize(deserializer)?;
-
-    let mut addr = inner
-        .to_socket_addrs()
-        .map_err(|err| Error::custom(format!("invalid hostname format: {err}")))?;
-
-    addr.next().ok_or_else(|| Error::missing_field("address"))
+    let s = String::deserialize(deserializer)?;
+    if !s.contains(':') {
+        return Err(Error::custom(format!(
+            "invalid socket address syntax, expected host:port: {s}"
+        )));
+    }
+    Ok(s)
 }
 
-impl From<ResolvableAddr> for SocketAddr {
-    fn from(addr: ResolvableAddr) -> Self {
-        addr.0
+impl ResolvableAddr {
+    pub fn resolve(&self) -> Option<SocketAddr> {
+        self.0.to_socket_addrs().ok()?.next()
     }
 }
diff --git a/src/server/router.rs b/src/server/router.rs
index 4aae8e7..ad2849b 100644
--- a/src/server/router.rs
+++ b/src/server/router.rs
@@ -7,6 +7,9 @@ use thiserror::Error;
 pub enum RouterError {
     #[error("no server with such hostname has been found")]
     NoServer,
+
+    #[error("backend server is currently unavailable")]
+    Unavailable,
 }
 
 // #[async_trait::async_trait]