diff --git a/elfo-network/src/config.rs b/elfo-network/src/config.rs
index 2c94f67..6bc50e3 100644
--- a/elfo-network/src/config.rs
+++ b/elfo-network/src/config.rs
@@ -26,7 +26,7 @@ use serde::{
 ///     "uds:///tmp/sock"
 /// ]
 /// ```
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Clone, Deserialize)]
 pub struct Config {
     /// A list of addresses to listen on.
     #[serde(default)]
@@ -59,7 +59,7 @@ pub struct Config {
 }
 
 /// Compression settings.
-#[derive(Debug, Default, Deserialize)]
+#[derive(Debug, Default, Deserialize, Clone)]
 pub struct CompressionConfig {
     /// Compression algorithm.
     #[serde(default)]
@@ -67,7 +67,7 @@ pub struct CompressionConfig {
 }
 
 /// Compression algorithms.
-#[derive(Debug, Default, PartialEq, Eq, Deserialize)]
+#[derive(Debug, Default, PartialEq, Eq, Deserialize, Clone)]
 pub enum CompressionAlgorithm {
     /// LZ4 with default compression level.
     Lz4,
@@ -85,7 +85,7 @@ fn default_idle_timeout() -> Duration {
 }
 
 /// How to discover other nodes.
-#[derive(Debug, Deserialize, Default)]
+#[derive(Debug, Deserialize, Clone, Default)]
 pub struct DiscoveryConfig {
     /// Predefined list of transports to connect to.
     pub predefined: Vec<Transport>,
diff --git a/elfo-network/src/discovery/diff.rs b/elfo-network/src/discovery/diff.rs
new file mode 100644
index 0000000..cdb8f59
--- /dev/null
+++ b/elfo-network/src/discovery/diff.rs
@@ -0,0 +1,100 @@
+#[cfg_attr(test, derive(Debug))]
+pub(crate) struct Diff<T> {
+    pub(crate) new: Vec<T>,
+    pub(crate) removed: fxhash::FxHashSet<T>,
+}
+
+impl<T> Diff<T> {
+    pub(crate) fn make<'a, I>(old: fxhash::FxHashSet<T>, new: I) -> Self
+    where
+        T: std::hash::Hash + Eq + Clone + 'a,
+        I: IntoIterator<Item = &'a T>,
+    {
+        let mut new_items = Vec::new();
+        let mut removed = old;
+        // Iterate over `new` version, removing each item from the
+        // `removed` set. Thus, the `removed` set in the end will
+        // contain items which are present in `old`, but not present
+        // in `new` - those elements are removed.
+        for item in new {
+            // If `removed` set previously didn't contain the item, then
+            // it's new.
+            let had = removed.remove(item);
+            if !had {
+                new_items.push(item.clone());
+            }
+        }
+
+        Self {
+            new: new_items,
+            removed,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    impl<T: Eq + Ord + Clone> PartialEq for Diff<T> {
+        fn eq(&self, other: &Self) -> bool {
+            let mut lhs_new = self.new.clone();
+            let mut lhs_removed = self.removed.iter().cloned().collect::<Vec<_>>();
+
+            lhs_new.sort();
+            lhs_removed.sort();
+
+            let mut rhs_new = other.new.clone();
+            let mut rhs_removed = other.removed.iter().cloned().collect::<Vec<_>>();
+
+            rhs_new.sort();
+            rhs_removed.sort();
+
+            (lhs_new == rhs_new) && (lhs_removed == rhs_removed)
+        }
+    }
+    impl<T: Eq + Ord + Clone> Eq for Diff<T> {}
+
+    #[test]
+    fn diff_works() {
+        struct Input {
+            old: Vec<u64>,
+            new: Vec<u64>,
+            expected: Diff<u64>,
+        }
+
+        impl Input {
+            fn new(
+                old: impl AsRef<[u64]>,
+                new: impl AsRef<[u64]>,
+                expected: (impl AsRef<[u64]>, impl AsRef<[u64]>),
+            ) -> Self {
+                let old = old.as_ref();
+                let new = new.as_ref();
+                let (diff_new, diff_removed) = (expected.0.as_ref(), expected.1.as_ref());
+
+                Self {
+                    old: old.to_vec(),
+                    new: new.to_vec(),
+                    expected: Diff {
+                        new: diff_new.to_vec(),
+                        removed: diff_removed.iter().copied().collect(),
+                    },
+                }
+            }
+        }
+
+        let inputs = [
+            Input::new([], [], ([], [])),
+            Input::new([1, 2, 3], [1, 2, 3], ([], [])),
+            Input::new([1, 2, 3], [1, 3], ([], [2])),
+            Input::new([1, 2, 3], [1, 2, 3, 4], ([4], [])),
+            Input::new([1, 2, 3], [1, 3, 4], ([4], [2])),
+        ];
+        for Input { new, old, expected } in inputs {
+            let actual = Diff::make(old.into_iter().collect(), new.iter());
+
+            assert_eq!(expected, actual);
+        }
+    }
+}
diff --git a/elfo-network/src/discovery/mod.rs b/elfo-network/src/discovery/mod.rs
index 6a0dee2..05ba34e 100644
--- a/elfo-network/src/discovery/mod.rs
+++ b/elfo-network/src/discovery/mod.rs
@@ -1,4 +1,4 @@
-use std::{future::Future, sync::Arc, time::Duration};
+use std::{future::Future, mem, sync::Arc, time::Duration};
 
 use eyre::{bail, eyre, Result, WrapErr};
 use futures::StreamExt;
@@ -12,13 +12,17 @@ use elfo_core::{
 
 use crate::{
     codec::format::{NetworkAddr, NetworkEnvelope, NetworkEnvelopePayload},
-    config::{CompressionAlgorithm, Transport},
+    config::{self, CompressionAlgorithm, Transport},
     node_map::{NodeInfo, NodeMap},
     protocol::{internode, DataConnectionFailed, GroupInfo, HandleConnection},
     socket::{self, ReadError, Socket},
     NetworkContext,
 };
 
+use self::diff::Diff;
+
+mod diff;
+
 /// Initial window size of every flow.
 /// TODO: should be different for groups and actors.
 const INITIAL_WINDOW_SIZE: i32 = 100_000;
@@ -69,6 +73,7 @@ struct ControlConnectionFailed {
 }
 
 pub(super) struct Discovery {
+    cfg: config::Config,
     ctx: NetworkContext,
     node_map: Arc<NodeMap>,
 }
@@ -82,7 +87,9 @@ pub(super) struct Discovery {
 
 impl Discovery {
     pub(super) fn new(ctx: NetworkContext, topology: Topology) -> Self {
+        let cfg = ctx.config().clone();
         Self {
+            cfg,
             ctx,
             node_map: Arc::new(NodeMap::new(&topology)),
         }
@@ -97,14 +104,12 @@ impl Discovery {
             )));
 
         self.listen().await?;
-        self.discover();
+        self.discover_all();
 
         while let Some(envelope) = self.ctx.recv().await {
             msg!(match envelope {
                 ConfigUpdated => {
-                    // TODO: update listeners.
-                    // TODO: stop discovering for removed transports.
-                    // TODO: self.discover();
+                    self.on_update_config();
                 }
                 msg @ ConnectionEstablished => self.on_connection_established(msg),
                 msg @ ConnectionAccepted => self.on_connection_accepted(msg),
@@ -121,7 +126,7 @@ impl Discovery {
                 msg @ ControlConnectionFailed => {
                     if let Some(transport) = msg.transport {
                         tokio::time::sleep(std::time::Duration::from_secs(5)).await;
-                        self.discover_one(transport);
+                        self.discover(transport);
                     }
                 }
             });
@@ -132,19 +137,52 @@ impl Discovery {
 
     fn get_capabilities(&self) -> socket::Capabilities {
         let mut capabilities = socket::Capabilities::empty();
-        if self.ctx.config().compression.algorithm == CompressionAlgorithm::Lz4 {
+        if self.cfg.compression.algorithm == CompressionAlgorithm::Lz4 {
             capabilities |= socket::Capabilities::LZ4;
         }
         capabilities
     }
 
+    fn on_update_config(&mut self) {
+        // TODO: Update listeners.
+        let cfg = self.ctx.config().clone();
+        let old = mem::replace(&mut self.cfg, cfg);
+
+        self.update_discovery(old.discovery);
+    }
+
+    fn update_discovery(&mut self, old: config::DiscoveryConfig) {
+        let config::DiscoveryConfig {
+            predefined,
+            attempt_interval: _,
+        } = old;
+
+        {
+            let Diff { new, removed } = Diff::make(
+                predefined.into_iter().collect(),
+                self.ctx.config().discovery.predefined.iter(),
+            );
+            for transport in new {
+                self.discover(transport);
+            }
+
+            // FIXME: handle removal.
+            if !removed.is_empty() {
+                warn!(
+                    ?removed,
+                    "got removal of several discovery.predefined entries, this is not supported as of now"
+                );
+            }
+        }
+    }
+
     async fn listen(&mut self) -> Result<()> {
         let node_no = self.node_map.this.node_no;
         let launch_id = self.node_map.this.launch_id;
         let capabilities = self.get_capabilities();
 
-        for transport in self.ctx.config().listen.clone() {
-            let stream = socket::listen(&transport, node_no, launch_id, capabilities)
+        for transport in &self.cfg.listen {
+            let stream = socket::listen(transport, node_no, launch_id, capabilities)
                 .await
                 .wrap_err_with(|| eyre!("cannot listen {}", transport))?
                 .filter_map(move |socket| async move {
@@ -176,13 +214,13 @@ impl Discovery {
         Ok(())
     }
 
-    fn discover(&mut self) {
-        for transport in self.ctx.config().discovery.predefined.clone() {
-            self.discover_one(transport);
+    fn discover_all(&mut self) {
+        for transport in self.cfg.discovery.predefined.clone() {
+            self.discover(transport);
         }
     }
 
-    fn discover_one(&mut self, transport: Transport) {
+    fn discover(&mut self, transport: Transport) {
         let msg = internode::SwitchToControl {
             groups: self.node_map.this.groups.clone(),
         };
@@ -194,7 +232,7 @@ impl Discovery {
         transport: &Transport,
         role: ConnectionRole,
     ) -> Stream<ConnectionEstablished> {
-        let interval = self.ctx.config().discovery.attempt_interval;
+        let interval = self.cfg.discovery.attempt_interval;
         let transport = transport.clone();
         let node_no = self.node_map.this.node_no;
         let launch_id = self.node_map.this.launch_id;
@@ -254,7 +292,7 @@ impl Discovery {
         );
 
         let node_map = self.node_map.clone();
-        let idle_timeout = self.ctx.config().idle_timeout;
+        let idle_timeout = self.cfg.idle_timeout;
         self.ctx.attach(Stream::once(async move {
             let info = socket.info.clone();
             let peer = socket.peer.clone();