diff --git a/beacon_chain/nimbus_beacon_node.nim b/beacon_chain/nimbus_beacon_node.nim
index 1a9101a90..e6778b966 100644
--- a/beacon_chain/nimbus_beacon_node.nim
+++ b/beacon_chain/nimbus_beacon_node.nim
@@ -793,9 +793,30 @@ proc removePhase0MessageHandlers(node: BeaconNode) =
 proc addAltairMessageHandlers(node: BeaconNode, slot: Slot) =
   node.addPhase0MessageHandlers(node.dag.forkDigests.altair)
 
+  var syncnets: BitArray[SYNC_COMMITTEE_SUBNET_COUNT]
+
+  # TODO: What are the best topic params for this?
+  for committeeIdx in allSyncCommittees():
+    closureScope:
+      let idx = committeeIdx
+      # TODO This should be done in dynamic way in trackSyncCommitteeTopics
+      node.network.subscribe(getSyncCommitteeTopic(node.dag.forkDigests.altair, idx), basicParams)
+      syncnets.setBit(idx.asInt)
+
+  node.network.subscribe(getSyncCommitteeContributionAndProofTopic(node.dag.forkDigests.altair), basicParams)
+  node.network.updateSyncnetsMetadata(syncnets)
+
 proc removeAltairMessageHandlers(node: BeaconNode) =
   node.removePhase0MessageHandlers(node.dag.forkDigests.altair)
 
+  for committeeIdx in allSyncCommittees():
+    closureScope:
+      let idx = committeeIdx
+      # TODO This should be done in dynamic way in trackSyncCommitteeTopics
+      node.network.unsubscribe(getSyncCommitteeTopic(node.dag.forkDigests.altair, idx))
+
+  node.network.unsubscribe(getSyncCommitteeContributionAndProofTopic(node.dag.forkDigests.altair))
+
 func getTopicSubscriptionEnabled(node: BeaconNode): bool =
   node.attestationSubnets.enabled
 
@@ -820,7 +841,11 @@ proc setupDoppelgangerDetection(node: BeaconNode, slot: Slot) =
     broadcastStartEpoch =
       node.processor.doppelgangerDetection.broadcastStartEpoch
 
-proc updateGossipStatus(node: BeaconNode, slot: Slot) =
+proc trackSyncCommitteeTopics*(node: BeaconNode) =
+  # TODO
+  discard
+
+proc updateGossipStatus(node: BeaconNode, slot: Slot) {.raises: [Defect, CatchableError].} =
   # Syncing tends to be ~1 block/s, and allow for an epoch of time for libp2p
   # subscribing to spin up. The faster the sync, the more wallSlot - headSlot
   # lead time is required
@@ -1256,6 +1281,20 @@ proc installMessageValidators(node: BeaconNode) =
     proc (signedVoluntaryExit: SignedVoluntaryExit): ValidationResult =
       node.processor[].voluntaryExitValidator(signedVoluntaryExit))
 
+  for committeeIdx in allSyncCommittees():
+    closureScope:
+      let idx = committeeIdx
+      node.network.addValidator(
+        getSyncCommitteeTopic(node.dag.forkDigests.altair, idx),
+        # This proc needs to be within closureScope; don't lift out of loop.
+        proc(msg: SyncCommitteeMessage): ValidationResult =
+          node.processor.syncCommitteeMsgValidator(msg, idx))
+
+  node.network.addValidator(
+    getSyncCommitteeContributionAndProofTopic(node.dag.forkDigests.altair),
+    proc(msg: SignedContributionAndProof): ValidationResult =
+      node.processor.syncCommitteeContributionValidator(msg))
+
 proc stop*(node: BeaconNode) =
   bnStatus = BeaconNodeStatus.Stopping
   notice "Graceful shutdown"