diff --git a/include/commissioner/commissioner.hpp b/include/commissioner/commissioner.hpp
index 8ab598d74..3fbc3b981 100644
--- a/include/commissioner/commissioner.hpp
+++ b/include/commissioner/commissioner.hpp
@@ -503,19 +503,6 @@ class Commissioner
      */
     virtual Error Resign() = 0;
 
-    /**
-     * @brief Set the Mesh-local Prefix of current connected Thread network.
-     *
-     * The user should get the Mesh-local Prefix with `GetActiveDataset` and set the prefix
-     * with this method, before initiating any other MGMT commands.
-     *
-     * @param[in] aMeshLocalPrefix  The Mesh-local Prefix of current Thread network.
-     *
-     * @retval Error::kNone         Successfully set the Mesh-local Prefix.
-     * @retval Error::kInvalidArgs  The Mesh-local Prefix is not valid.
-     */
-    virtual Error SetMeshLocalPrefix(const ByteArray &aMeshLocalPrefix) = 0;
-
     /**
      * @brief Asynchronously get the Commissioner Dataset.
      *
diff --git a/include/commissioner/defines.hpp b/include/commissioner/defines.hpp
index 81bfdc1fe..c3fe5614a 100644
--- a/include/commissioner/defines.hpp
+++ b/include/commissioner/defines.hpp
@@ -123,11 +123,6 @@ static constexpr uint16_t kDefaultAeUdpPort = 1001;
  */
 static constexpr uint16_t kDefaultNmkpUdpPort = 1002;
 
-/**
- * The fixed primary backbone router anycast locator.
- */
-static constexpr uint16_t kPrimaryBbrAloc16 = 0xFC38;
-
 /**
  * If using radio 915Mhz. Default radio freq of Thread is 2.4Ghz.
  *
diff --git a/src/app/commissioner_app.cpp b/src/app/commissioner_app.cpp
index 4a19ae821..248cd9861 100644
--- a/src/app/commissioner_app.cpp
+++ b/src/app/commissioner_app.cpp
@@ -151,7 +151,6 @@ Error CommissionerApp::SyncNetworkData(void)
     BbrDataset                bbrDataset;
 
     SuccessOrExit(error = mCommissioner->GetActiveDataset(activeDataset, 0xFFFF));
-    SuccessOrExit(error = mCommissioner->SetMeshLocalPrefix(activeDataset.mMeshLocalPrefix));
     SuccessOrExit(error = mCommissioner->GetPendingDataset(pendingDataset, 0xFFFF));
     SuccessOrExit(error = mCommissioner->SetCommissionerDataset(mCommDataset));
     if (IsCcmMode())
diff --git a/src/library/commissioner_impl.cpp b/src/library/commissioner_impl.cpp
index 9180fcbac..04e531f76 100644
--- a/src/library/commissioner_impl.cpp
+++ b/src/library/commissioner_impl.cpp
@@ -48,9 +48,8 @@ namespace ot {
 
 namespace commissioner {
 
-static constexpr size_t kMeshLocalPrefixLength = 8;
-
-static constexpr uint16_t kLeaderAloc16 = 0xFC00;
+static constexpr uint16_t kLeaderAloc16     = 0xFC00;
+static constexpr uint16_t kPrimaryBbrAloc16 = 0xFC38;
 
 static constexpr uint16_t kDefaultMmPort = 61631;
 
@@ -128,7 +127,7 @@ CommissionerImpl::CommissionerImpl(CommissionerHandler &aHandler, struct event_b
     , mJoinerSessionTimer(mEventBase, [this](Timer &aTimer) { HandleJoinerSessionTimer(aTimer); })
     , mResourceUdpRx(uri::kUdpRx, [this](const coap::Request &aRequest) { mProxyClient.HandleUdpRx(aRequest); })
     , mResourceRlyRx(uri::kRelayRx, [this](const coap::Request &aRequest) { HandleRlyRx(aRequest); })
-    , mProxyClient(mEventBase, mBrClient)
+    , mProxyClient(*this, mBrClient)
 #if OT_COMM_CONFIG_CCM_ENABLE
     , mTokenManager(mEventBase)
 #endif
@@ -281,7 +280,6 @@ void CommissionerImpl::Resign(ErrorHandler aHandler)
     }
 
     Disconnect();
-    mMeshLocalPrefix.clear();
 
     aHandler(ERROR_NONE);
 }
@@ -295,6 +293,7 @@ void CommissionerImpl::Connect(ErrorHandler aHandler, const std::string &aAddr,
 void CommissionerImpl::Disconnect()
 {
     mBrClient.Disconnect(ERROR_CANCELLED("the CoAPs client was disconnected"));
+    mProxyClient.ClearMeshLocalPrefix();
     mState = State::kDisabled;
 }
 
@@ -336,27 +335,6 @@ void CommissionerImpl::CancelRequests()
 #endif
 }
 
-Error CommissionerImpl::SetMeshLocalPrefix(const ByteArray &aMeshLocalPrefix)
-{
-    constexpr uint8_t meshLocalPrefix[] = {0xfd};
-    Error             error;
-
-    VerifyOrExit(!aMeshLocalPrefix.empty(), error = ERROR_NONE);
-    VerifyOrExit(aMeshLocalPrefix.size() == kMeshLocalPrefixLength,
-                 error = ERROR_INVALID_ARGS("Thread Mesh-local Prefix length must be {}", kMeshLocalPrefixLength));
-    VerifyOrExit(
-        std::equal(aMeshLocalPrefix.begin(), aMeshLocalPrefix.begin() + sizeof(meshLocalPrefix), meshLocalPrefix),
-        error = ERROR_INVALID_ARGS("Thread mesh-local Prefix must starts with fd00::/8"));
-    error = ERROR_NONE;
-
-exit:
-    if (error == ErrorCode::kNone)
-    {
-        mMeshLocalPrefix = aMeshLocalPrefix;
-    }
-    return error;
-}
-
 void CommissionerImpl::GetCommissionerDataset(Handler<CommissionerDataset> aHandler, uint16_t aDatasetFlags)
 {
     Error         error;
@@ -389,7 +367,7 @@ void CommissionerImpl::GetCommissionerDataset(Handler<CommissionerDataset> aHand
         SuccessOrExit(AppendTlv(request, {tlv::Type::kGet, tlvTypes}));
     }
 
-    mProxyClient.SendRequest(request, onResponse, GetLeaderLocator(), kDefaultMmPort);
+    mProxyClient.SendRequest(request, onResponse, kLeaderAloc16, kDefaultMmPort);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MGMT_COMMISSIONER_GET.req");
 
@@ -429,7 +407,7 @@ void CommissionerImpl::SetCommissionerDataset(ErrorHandler aHandler, const Commi
     }
 #endif
 
-    mProxyClient.SendRequest(request, onResponse, GetLeaderLocator(), kDefaultMmPort);
+    mProxyClient.SendRequest(request, onResponse, kLeaderAloc16, kDefaultMmPort);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MGMT_COMMISSIONER_SET.req");
 
@@ -495,15 +473,10 @@ void CommissionerImpl::GetRawActiveDataset(Handler<ByteArray> aHandler, uint16_t
     }
 #endif
 
-    if (mMeshLocalPrefix.empty())
-    {
-        // Request Active Dataset from the BA when we don't possess the mesh-local prefix.
-        mBrClient.SendRequest(request, onResponse);
-    }
-    else
-    {
-        mProxyClient.SendRequest(request, onResponse, GetLeaderLocator(), kDefaultMmPort);
-    }
+    // Always request Active Dataset from the Border Agent because
+    // the Mesh-Local prefix of current network is agnostic before
+    // we requesting the latest Active Operational Dataset.
+    mBrClient.SendRequest(request, onResponse);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MGMT_ACTIVE_GET.req");
 
@@ -541,7 +514,6 @@ void CommissionerImpl::SetActiveDataset(ErrorHandler aHandler, const ActiveOpera
                                             "try setting with Pending Operational Dataset instead"));
 
     VerifyOrExit(IsActive(), error = ERROR_INVALID_STATE("the commissioner is not active"));
-    VerifyOrExit(!mMeshLocalPrefix.empty(), error = ERROR_INVALID_STATE("no valid Mesh-local Prefix is set"));
     SuccessOrExit(error = request.SetUriPath(uri::kMgmtActiveSet));
     SuccessOrExit(error = AppendTlv(request, {tlv::Type::kCommissionerSessionId, GetSessionId()}));
     SuccessOrExit(error = EncodeActiveOperationalDataset(request, aDataset));
@@ -553,7 +525,7 @@ void CommissionerImpl::SetActiveDataset(ErrorHandler aHandler, const ActiveOpera
     }
 #endif
 
-    mProxyClient.SendRequest(request, onResponse, GetLeaderLocator(), kDefaultMmPort);
+    mProxyClient.SendRequest(request, onResponse, kLeaderAloc16, kDefaultMmPort);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MGMT_ACTIVE_SET.req");
 
@@ -594,7 +566,6 @@ void CommissionerImpl::GetPendingDataset(Handler<PendingOperationalDataset> aHan
     };
 
     VerifyOrExit(IsActive(), error = ERROR_INVALID_STATE("the commissioner is not active"));
-    VerifyOrExit(!mMeshLocalPrefix.empty(), error = ERROR_INVALID_STATE("no valid Mesh-local Prefix is set"));
     SuccessOrExit(error = request.SetUriPath(uri::kMgmtPendingGet));
     if (!datasetList.empty())
     {
@@ -608,7 +579,7 @@ void CommissionerImpl::GetPendingDataset(Handler<PendingOperationalDataset> aHan
     }
 #endif
 
-    mProxyClient.SendRequest(request, onResponse, GetLeaderLocator(), kDefaultMmPort);
+    mProxyClient.SendRequest(request, onResponse, kLeaderAloc16, kDefaultMmPort);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MGMT_PENDING_GET.req");
 
@@ -637,7 +608,6 @@ void CommissionerImpl::SetPendingDataset(ErrorHandler aHandler, const PendingOpe
                  error = ERROR_INVALID_ARGS("Delay Timer is mandatory for a Pending Operational Dataset"));
 
     VerifyOrExit(IsActive(), error = ERROR_INVALID_STATE("the commissioner is not active"));
-    VerifyOrExit(!mMeshLocalPrefix.empty(), error = ERROR_INVALID_STATE("no valid Mesh-local Prefix is set"));
     SuccessOrExit(error = request.SetUriPath(uri::kMgmtPendingSet));
     SuccessOrExit(error = AppendTlv(request, {tlv::Type::kCommissionerSessionId, GetSessionId()}));
     SuccessOrExit(error = EncodePendingOperationalDataset(request, aDataset));
@@ -649,7 +619,7 @@ void CommissionerImpl::SetPendingDataset(ErrorHandler aHandler, const PendingOpe
     }
 #endif
 
-    mProxyClient.SendRequest(request, onResponse, GetLeaderLocator(), kDefaultMmPort);
+    mProxyClient.SendRequest(request, onResponse, kLeaderAloc16, kDefaultMmPort);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MGMT_PENDING_SET.req");
 
@@ -672,8 +642,6 @@ void CommissionerImpl::SetBbrDataset(ErrorHandler aHandler, const BbrDataset &aD
     };
 
     VerifyOrExit(IsActive(), error = ERROR_INVALID_STATE("the commissioner is not active"));
-    VerifyOrExit(!mMeshLocalPrefix.empty(), error = ERROR_INVALID_STATE("no valid Mesh-local Prefix is set"));
-
     VerifyOrExit(IsCcmMode(), error = ERROR_INVALID_STATE("sending MGMT_BBR_SET.req is only valid in CCM mode"));
     VerifyOrExit((aDataset.mPresentFlags & BbrDataset::kRegistrarIpv6AddrBit) == 0,
                  error = ERROR_INVALID_ARGS("trying to set Registrar IPv6 Address which is read-only"));
@@ -687,7 +655,7 @@ void CommissionerImpl::SetBbrDataset(ErrorHandler aHandler, const BbrDataset &aD
         SuccessOrExit(error = SignRequest(request));
     }
 
-    mProxyClient.SendRequest(request, onResponse, GetLeaderLocator(), kDefaultMmPort);
+    mProxyClient.SendRequest(request, onResponse, kLeaderAloc16, kDefaultMmPort);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MGMT_BBR_SET.req");
 
@@ -724,7 +692,6 @@ void CommissionerImpl::GetBbrDataset(Handler<BbrDataset> aHandler, uint16_t aDat
     };
 
     VerifyOrExit(IsActive(), error = ERROR_INVALID_STATE("the commissioner is not active"));
-    VerifyOrExit(!mMeshLocalPrefix.empty(), error = ERROR_INVALID_STATE("no valid Mesh-local Prefix is set"));
     VerifyOrExit(IsCcmMode(), error = ERROR_INVALID_STATE("sending MGMT_BBR_GET.req is only valid in CCM mode"));
 
     SuccessOrExit(error = request.SetUriPath(uri::kMgmtBbrGet));
@@ -734,7 +701,7 @@ void CommissionerImpl::GetBbrDataset(Handler<BbrDataset> aHandler, uint16_t aDat
         SuccessOrExit(error = AppendTlv(request, {tlv::Type::kGet, datasetList}));
     }
 
-    mProxyClient.SendRequest(request, onResponse, GetLeaderLocator(), kDefaultMmPort);
+    mProxyClient.SendRequest(request, onResponse, kLeaderAloc16, kDefaultMmPort);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MGMT_BBR_GET.req");
 
@@ -759,19 +726,35 @@ void CommissionerImpl::SetSecurePendingDataset(ErrorHandler
         aHandler(HandleStateResponse(aResponse, aError));
     };
 
+    auto onMeshLocalPrefixResponse = [=](Error aError) {
+        if (aError == ErrorCode::kNone)
+        {
+            SetSecurePendingDataset(aHandler, aMaxRetrievalTimer, aDataset);
+        }
+        else
+        {
+            aHandler(aError);
+        }
+    };
+
     // Delay timer is mandatory.
     VerifyOrExit(aDataset.mPresentFlags & PendingOperationalDataset::kDelayTimerBit,
                  error = ERROR_INVALID_ARGS("Delay Timer is mandatory for a Secure Pending Operational Dataset"));
 
     VerifyOrExit(IsActive(), error = ERROR_INVALID_STATE("the commissioner is not active"));
-    VerifyOrExit(!mMeshLocalPrefix.empty(), error = ERROR_INVALID_STATE("no valid Mesh-local Prefix is set"));
     VerifyOrExit(IsCcmMode(),
                  error = ERROR_INVALID_STATE("sending MGMT_SEC_PENDING_SET.req is only valid in CCM mode"));
 
+    if (mProxyClient.GetMeshLocalPrefix().empty())
+    {
+        mProxyClient.FetchMeshLocalPrefix(onMeshLocalPrefixResponse);
+        ExitNow();
+    }
+
     SuccessOrExit(error = request.SetUriPath(uri::kMgmtSecPendingSet));
     SuccessOrExit(error = AppendTlv(request, {tlv::Type::kCommissionerSessionId, GetSessionId()}));
 
-    pbbrAddr = GetPrimaryBbrLocator();
+    pbbrAddr = mProxyClient.GetAnycastLocator(kPrimaryBbrAloc16);
     uri      = "coaps://[" + pbbrAddr.ToString() + "]" + uri::kMgmtPendingGet;
 
     utils::Encode(secureDissemination, aDataset.mPendingTimestamp.Encode());
@@ -988,7 +971,6 @@ void CommissionerImpl::RegisterMulticastListener(Handler<uint8_t>
     }
 
     VerifyOrExit(IsActive(), error = ERROR_INVALID_STATE("the commissioner is not active"));
-    VerifyOrExit(!mMeshLocalPrefix.empty(), error = ERROR_INVALID_STATE("no valid Mesh-local Prefix is set"));
     SuccessOrExit(error = request.SetUriPath(uri::kMlr));
     SuccessOrExit(
         error = AppendTlv(request, {tlv::Type::kThreadCommissionerSessionId, GetSessionId(), tlv::Scope::kThread}));
@@ -1002,7 +984,7 @@ void CommissionerImpl::RegisterMulticastListener(Handler<uint8_t>
     }
 #endif
 
-    mProxyClient.SendRequest(request, onResponse, GetPrimaryBbrLocator(), kDefaultMmPort);
+    mProxyClient.SendRequest(request, onResponse, kPrimaryBbrAloc16, kDefaultMmPort);
 
     LOG_DEBUG(LOG_REGION_MGMT, "sent MLR.req");
 
@@ -1975,6 +1957,11 @@ void CommissionerImpl::HandleDatasetChanged(const coap::Request &aRequest)
 
     mProxyClient.SendEmptyChanged(aRequest);
 
+    // Clear the cached Mesh-Local prefix so that the UDP Proxy client
+    // will request for the new Mesh-Local prefix before sending next
+    // UDP_TX.ntf message.
+    mProxyClient.ClearMeshLocalPrefix();
+
     mCommissionerHandler.OnDatasetChanged();
 }
 
@@ -2197,35 +2184,6 @@ void CommissionerImpl::HandleJoinerSessionTimer(Timer &aTimer)
     }
 }
 
-Address CommissionerImpl::GetAnycastLocator(uint16_t aAloc16) const
-{
-    ASSERT(!mMeshLocalPrefix.empty());
-
-    Address   ret;
-    Error     error;
-    ByteArray alocAddr = mMeshLocalPrefix;
-
-    utils::Encode<uint16_t>(alocAddr, 0x0000);
-    utils::Encode<uint16_t>(alocAddr, 0x00FF);
-    utils::Encode<uint16_t>(alocAddr, 0xFE00);
-    utils::Encode<uint16_t>(alocAddr, aAloc16);
-
-    error = ret.Set(alocAddr);
-    ASSERT(error == ErrorCode::kNone);
-
-    return ret;
-}
-
-Address CommissionerImpl::GetLeaderLocator(void) const
-{
-    return GetAnycastLocator(kLeaderAloc16);
-}
-
-Address CommissionerImpl::GetPrimaryBbrLocator(void) const
-{
-    return GetAnycastLocator(kPrimaryBbrAloc16);
-}
-
 } // namespace commissioner
 
 } // namespace ot
diff --git a/src/library/commissioner_impl.hpp b/src/library/commissioner_impl.hpp
index 164d906b0..1e2a02eac 100644
--- a/src/library/commissioner_impl.hpp
+++ b/src/library/commissioner_impl.hpp
@@ -102,8 +102,6 @@ class CommissionerImpl : public Commissioner
     void  Resign(ErrorHandler aHandler) override;
     Error Resign() override { return ERROR_UNIMPLEMENTED(""); }
 
-    Error SetMeshLocalPrefix(const ByteArray &aMeshLocalPrefix) override;
-
     void  GetCommissionerDataset(Handler<CommissionerDataset> aHandler, uint16_t aDatasetFlags) override;
     Error GetCommissionerDataset(CommissionerDataset &, uint16_t) override { return ERROR_UNIMPLEMENTED(""); }
 
@@ -222,10 +220,6 @@ class CommissionerImpl : public Commissioner
 
     void SendPetition(PetitionHandler aHandler);
 
-    Address GetAnycastLocator(uint16_t aAloc16) const;
-    Address GetLeaderLocator(void) const;
-    Address GetPrimaryBbrLocator(void) const;
-
     // Set @p aKeepAlive to false to resign the commissioner role.
     void SendKeepAlive(Timer &aTimer, bool aKeepAlive = true);
 
@@ -264,7 +258,6 @@ class CommissionerImpl : public Commissioner
     Timer mKeepAliveTimer;
 
     coap::CoapSecure mBrClient;
-    ByteArray        mMeshLocalPrefix;
 
     std::map<ByteArray, JoinerSession> mJoinerSessions;
     Timer                              mJoinerSessionTimer;
diff --git a/src/library/commissioner_safe.cpp b/src/library/commissioner_safe.cpp
index 9e819dfe6..df83a8874 100644
--- a/src/library/commissioner_safe.cpp
+++ b/src/library/commissioner_safe.cpp
@@ -208,14 +208,6 @@ Error CommissionerSafe::Resign()
     return pro.get_future().get();
 }
 
-Error CommissionerSafe::SetMeshLocalPrefix(const ByteArray &aMeshLocalPrefix)
-{
-    std::promise<Error> pro;
-
-    PushAsyncRequest([&]() { pro.set_value(mImpl->SetMeshLocalPrefix(aMeshLocalPrefix)); });
-    return pro.get_future().get();
-}
-
 void CommissionerSafe::GetCommissionerDataset(Handler<CommissionerDataset> aHandler, uint16_t aDatasetFlags)
 {
     PushAsyncRequest([=]() { mImpl->GetCommissionerDataset(aHandler, aDatasetFlags); });
diff --git a/src/library/commissioner_safe.hpp b/src/library/commissioner_safe.hpp
index 6c697cb9a..5523cd6d0 100644
--- a/src/library/commissioner_safe.hpp
+++ b/src/library/commissioner_safe.hpp
@@ -103,8 +103,6 @@ class CommissionerSafe : public Commissioner
     void  Resign(ErrorHandler aHandler) override;
     Error Resign() override;
 
-    Error SetMeshLocalPrefix(const ByteArray &aMeshLocalPrefix) override;
-
     void  GetCommissionerDataset(Handler<CommissionerDataset> aHandler, uint16_t aDatasetFlags) override;
     Error GetCommissionerDataset(CommissionerDataset &aDataset, uint16_t aDatasetFlags) override;
 
diff --git a/src/library/udp_proxy.cpp b/src/library/udp_proxy.cpp
index f21e03a05..c115e5556 100644
--- a/src/library/udp_proxy.cpp
+++ b/src/library/udp_proxy.cpp
@@ -41,6 +41,15 @@ namespace ot {
 
 namespace commissioner {
 
+static constexpr size_t kMeshLocalPrefixLength = 8;
+
+ProxyClient::ProxyClient(CommissionerImpl &aCommissioner, coap::CoapSecure &aBrClient)
+    : mCommissioner(aCommissioner)
+    , mEndpoint(aBrClient)
+    , mCoap(aCommissioner.GetEventBase(), mEndpoint)
+{
+}
+
 /**
  * Encapsulate the request and send it as a UDP_TX.ntf message.
  */
@@ -75,6 +84,30 @@ Error ProxyEndpoint::Send(const ByteArray &aRequest, MessageSubType aSubType)
     return error;
 }
 
+void ProxyClient::SendRequest(const coap::Request & aRequest,
+                              coap::ResponseHandler aHandler,
+                              uint16_t              aPeerAloc16,
+                              uint16_t              aPeerPort)
+{
+    if (mMeshLocalPrefix.empty())
+    {
+        FetchMeshLocalPrefix([=](Error aError) {
+            if (aError == ErrorCode::kNone)
+            {
+                SendRequest(aRequest, aHandler, GetAnycastLocator(aPeerAloc16), aPeerPort);
+            }
+            else
+            {
+                aHandler(nullptr, aError);
+            }
+        });
+    }
+    else
+    {
+        SendRequest(aRequest, aHandler, GetAnycastLocator(aPeerAloc16), aPeerPort);
+    }
+}
+
 void ProxyClient::SendRequest(const coap::Request & aRequest,
                               coap::ResponseHandler aHandler,
                               const Address &       aPeerAddr,
@@ -129,6 +162,61 @@ void ProxyClient::HandleUdpRx(const coap::Request &aUdpRx)
     return;
 }
 
+void ProxyClient::FetchMeshLocalPrefix(Commissioner::ErrorHandler aHandler)
+{
+    auto onResponse = [=](const ActiveOperationalDataset *aActiveDataset, Error aError) {
+        Error error;
+
+        SuccessOrExit(error = aError);
+        ASSERT(aActiveDataset != nullptr);
+
+        VerifyOrExit(aActiveDataset->mPresentFlags & ActiveOperationalDataset::kMeshLocalPrefixBit,
+                     error = ERROR_BAD_FORMAT("Mesh-Local prefix not included in response"));
+        SuccessOrExit(error = SetMeshLocalPrefix(aActiveDataset->mMeshLocalPrefix));
+
+    exit:
+        aHandler(aError);
+    };
+
+    mCommissioner.GetActiveDataset(onResponse, ActiveOperationalDataset::kMeshLocalPrefixBit);
+}
+
+Error ProxyClient::SetMeshLocalPrefix(const ByteArray &aMeshLocalPrefix)
+{
+    constexpr uint8_t meshLocalPrefix[] = {0xfd};
+    Error             error;
+
+    VerifyOrExit(aMeshLocalPrefix.size() == kMeshLocalPrefixLength,
+                 error = ERROR_INVALID_ARGS("Thread Mesh-local Prefix length must be {}", kMeshLocalPrefixLength));
+    VerifyOrExit(
+        std::equal(aMeshLocalPrefix.begin(), aMeshLocalPrefix.begin() + sizeof(meshLocalPrefix), meshLocalPrefix),
+        error = ERROR_INVALID_ARGS("Thread mesh-local Prefix must starts with fd00::/8"));
+
+    mMeshLocalPrefix = aMeshLocalPrefix;
+
+exit:
+    return error;
+}
+
+Address ProxyClient::GetAnycastLocator(uint16_t aAloc16) const
+{
+    ASSERT(!mMeshLocalPrefix.empty());
+
+    Address   ret;
+    Error     error;
+    ByteArray alocAddr = mMeshLocalPrefix;
+
+    utils::Encode<uint16_t>(alocAddr, 0x0000);
+    utils::Encode<uint16_t>(alocAddr, 0x00FF);
+    utils::Encode<uint16_t>(alocAddr, 0xFE00);
+    utils::Encode<uint16_t>(alocAddr, aAloc16);
+
+    error = ret.Set(alocAddr);
+    ASSERT(error == ErrorCode::kNone);
+
+    return ret;
+}
+
 } // namespace commissioner
 
 } // namespace ot
diff --git a/src/library/udp_proxy.hpp b/src/library/udp_proxy.hpp
index 0bb5eeaea..f13f4fd94 100644
--- a/src/library/udp_proxy.hpp
+++ b/src/library/udp_proxy.hpp
@@ -44,6 +44,8 @@ namespace ot {
 
 namespace commissioner {
 
+class CommissionerImpl;
+
 // The UDP proxy endpoint that sends UDP data by encapsulating
 // it in the UDP_TX.ntf message.
 class ProxyEndpoint : public Endpoint
@@ -75,11 +77,12 @@ class ProxyEndpoint : public Endpoint
 class ProxyClient
 {
 public:
-    ProxyClient(struct event_base *aEventBase, coap::CoapSecure &aBrClient)
-        : mEndpoint(aBrClient)
-        , mCoap(aEventBase, mEndpoint)
-    {
-    }
+    ProxyClient(CommissionerImpl &aCommissioner, coap::CoapSecure &aBrClient);
+
+    void SendRequest(const coap::Request & aRequest,
+                     coap::ResponseHandler aHandler,
+                     uint16_t              aPeerAloc16,
+                     uint16_t              aPeerPort);
 
     void SendRequest(const coap::Request & aRequest,
                      coap::ResponseHandler aHandler,
@@ -96,9 +99,23 @@ class ProxyClient
 
     void CancelRequests() { mCoap.CancelRequests(); }
 
+    void FetchMeshLocalPrefix(Commissioner::ErrorHandler aHandler);
+
+    const ByteArray &GetMeshLocalPrefix(void) const { return mMeshLocalPrefix; }
+    void             ClearMeshLocalPrefix(void) { mMeshLocalPrefix.clear(); }
+
+    Error SetMeshLocalPrefix(const ByteArray &aMeshLocalPrefix);
+
+    Address GetAnycastLocator(uint16_t aAloc16) const;
+
 private:
-    ProxyEndpoint mEndpoint;
-    coap::Coap    mCoap;
+    CommissionerImpl &mCommissioner;
+    ProxyEndpoint     mEndpoint;
+    coap::Coap        mCoap;
+
+    // The Mesh-Local prefix of current connected Thread network.
+    // Used to compute Mesh-Local address of UDP_TX.ntf peer.
+    ByteArray mMeshLocalPrefix;
 };
 
 } // namespace commissioner