diff --git a/src/shrpx.cc b/src/shrpx.cc
index 018073bd..454206a4 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -146,52 +146,6 @@ struct SignalServer {
   pid_t worker_process_pid;
 };
 
-namespace {
-int resolve_hostname(Address *addr, const char *hostname, uint16_t port,
-                     int family) {
-  int rv;
-
-  auto service = util::utos(port);
-
-  addrinfo hints{};
-  hints.ai_family = family;
-  hints.ai_socktype = SOCK_STREAM;
-#ifdef AI_ADDRCONFIG
-  hints.ai_flags |= AI_ADDRCONFIG;
-#endif // AI_ADDRCONFIG
-  addrinfo *res;
-
-  rv = getaddrinfo(hostname, service.c_str(), &hints, &res);
-  if (rv != 0) {
-    LOG(FATAL) << "Unable to resolve address for " << hostname << ": "
-               << gai_strerror(rv);
-    return -1;
-  }
-
-  auto res_d = defer(freeaddrinfo, res);
-
-  char host[NI_MAXHOST];
-  rv = getnameinfo(res->ai_addr, res->ai_addrlen, host, sizeof(host), nullptr,
-                   0, NI_NUMERICHOST);
-  if (rv != 0) {
-    LOG(FATAL) << "Address resolution for " << hostname
-               << " failed: " << gai_strerror(rv);
-
-    return -1;
-  }
-
-  if (LOG_ENABLED(INFO)) {
-    LOG(INFO) << "Address resolution for " << hostname
-              << " succeeded: " << host;
-  }
-
-  memcpy(&addr->su, res->ai_addr, res->ai_addrlen);
-  addr->len = res->ai_addrlen;
-
-  return 0;
-}
-} // namespace
-
 namespace {
 int chown_to_running_user(const char *path) {
   return chown(path, get_config()->uid, get_config()->gid);
@@ -1075,11 +1029,6 @@ constexpr auto DEFAULT_ACCESSLOG_FORMAT = StringRef::from_lit(
     R"("$http_referer" "$http_user_agent")");
 } // namespace
 
-namespace {
-constexpr char DEFAULT_DOWNSTREAM_HOST[] = "127.0.0.1";
-constexpr int16_t DEFAULT_DOWNSTREAM_PORT = 80;
-} // namespace;
-
 namespace {
 void fill_default_config() {
   *mod_config() = {};
@@ -2151,7 +2100,6 @@ void process_options(int argc, char **argv,
 
   auto &listenerconf = mod_config()->conn.listener;
   auto &upstreamconf = mod_config()->conn.upstream;
-  auto &downstreamconf = mod_config()->conn.downstream;
 
   if (listenerconf.addrs.empty()) {
     UpstreamAddr addr{};
@@ -2185,140 +2133,11 @@ void process_options(int argc, char **argv,
     }
   }
 
-  auto &addr_groups = downstreamconf.addr_groups;
-
-  if (addr_groups.empty()) {
-    DownstreamAddrConfig addr{};
-    addr.host = ImmutableString::from_lit(DEFAULT_DOWNSTREAM_HOST);
-    addr.port = DEFAULT_DOWNSTREAM_PORT;
-    addr.proto = PROTO_HTTP1;
-
-    DownstreamAddrGroupConfig g(StringRef::from_lit("/"));
-    g.addrs.push_back(std::move(addr));
-    mod_config()->router.add_route(StringRef{g.pattern}, addr_groups.size());
-    addr_groups.push_back(std::move(g));
-  } else if (get_config()->http2_proxy) {
-    // We don't support host mapping in these cases.  Move all
-    // non-catch-all patterns to catch-all pattern.
-    DownstreamAddrGroupConfig catch_all(StringRef::from_lit("/"));
-    for (auto &g : addr_groups) {
-      std::move(std::begin(g.addrs), std::end(g.addrs),
-                std::back_inserter(catch_all.addrs));
-    }
-    std::vector<DownstreamAddrGroupConfig>().swap(addr_groups);
-    std::vector<WildcardPattern>().swap(mod_config()->wildcard_patterns);
-    // maybe not necessary?
-    mod_config()->router = Router();
-    mod_config()->router.add_route(StringRef{catch_all.pattern},
-                                   addr_groups.size());
-    addr_groups.push_back(std::move(catch_all));
-  } else {
-    auto &wildcard_patterns = mod_config()->wildcard_patterns;
-    std::sort(std::begin(wildcard_patterns), std::end(wildcard_patterns),
-              [](const WildcardPattern &lhs, const WildcardPattern &rhs) {
-                return std::lexicographical_compare(
-                    rhs.host.rbegin(), rhs.host.rend(), lhs.host.rbegin(),
-                    lhs.host.rend());
-              });
-    if (LOG_ENABLED(INFO)) {
-      LOG(INFO) << "Reverse sorted wildcard hosts (compared from tail to head, "
-                   "and sorted in reverse order):";
-      for (auto &wp : mod_config()->wildcard_patterns) {
-        LOG(INFO) << wp.host;
-      }
-    }
-  }
-
-  // backward compatibility: override all SNI fields with the option
-  // value --backend-tls-sni-field
-  if (!tlsconf.backend_sni_name.empty()) {
-    auto &sni = tlsconf.backend_sni_name;
-    for (auto &addr_group : addr_groups) {
-      for (auto &addr : addr_group.addrs) {
-        addr.sni = sni;
-      }
-    }
-  }
-
-  if (LOG_ENABLED(INFO)) {
-    LOG(INFO) << "Resolving backend address";
-  }
-
-  ssize_t catch_all_group = -1;
-  for (size_t i = 0; i < addr_groups.size(); ++i) {
-    auto &g = addr_groups[i];
-    if (g.pattern == StringRef::from_lit("/")) {
-      catch_all_group = i;
-    }
-    if (LOG_ENABLED(INFO)) {
-      LOG(INFO) << "Host-path pattern: group " << i << ": '" << g.pattern
-                << "'";
-      for (auto &addr : g.addrs) {
-        LOG(INFO) << "group " << i << " -> " << addr.host.c_str()
-                  << (addr.host_unix ? "" : ":" + util::utos(addr.port))
-                  << ", proto=" << strproto(addr.proto)
-                  << (addr.tls ? ", tls" : "");
-      }
-    }
-  }
-
-  if (catch_all_group == -1) {
-    LOG(FATAL) << "backend: No catch-all backend address is configured";
+  if (configure_downstream_group(mod_config(), get_config()->http2_proxy, false,
+                                 tlsconf) != 0) {
     exit(EXIT_FAILURE);
   }
 
-  downstreamconf.addr_group_catch_all = catch_all_group;
-
-  if (LOG_ENABLED(INFO)) {
-    LOG(INFO) << "Catch-all pattern is group " << catch_all_group;
-  }
-
-  for (auto &g : addr_groups) {
-    for (auto &addr : g.addrs) {
-
-      if (addr.host_unix) {
-        // for AF_UNIX socket, we use "localhost" as host for backend
-        // hostport.  This is used as Host header field to backend and
-        // not going to be passed to any syscalls.
-        addr.hostport = "localhost";
-
-        auto path = addr.host.c_str();
-        auto pathlen = addr.host.size();
-
-        if (pathlen + 1 > sizeof(addr.addr.su.un.sun_path)) {
-          LOG(FATAL) << "UNIX domain socket path " << path << " is too long > "
-                     << sizeof(addr.addr.su.un.sun_path);
-          exit(EXIT_FAILURE);
-        }
-
-        if (LOG_ENABLED(INFO)) {
-          LOG(INFO) << "Use UNIX domain socket path " << path
-                    << " for backend connection";
-        }
-
-        addr.addr.su.un.sun_family = AF_UNIX;
-        // copy path including terminal NULL
-        std::copy_n(path, pathlen + 1, addr.addr.su.un.sun_path);
-        addr.addr.len = sizeof(addr.addr.su.un);
-
-        continue;
-      }
-
-      addr.hostport = ImmutableString(
-          util::make_http_hostport(StringRef(addr.host), addr.port));
-
-      auto hostport = util::make_hostport(StringRef{addr.host}, addr.port);
-
-      if (resolve_hostname(&addr.addr, addr.host.c_str(), addr.port,
-                           downstreamconf.family) == -1) {
-        LOG(FATAL) << "Resolving backend address failed: " << hostport;
-        exit(EXIT_FAILURE);
-      }
-      LOG(NOTICE) << "Resolved backend address: " << hostport << " -> "
-                  << util::to_numeric_addr(&addr.addr);
-    }
-  }
-
   auto &proxy = mod_config()->downstream_http_proxy;
   if (!proxy.host.empty()) {
     auto hostport = util::make_hostport(StringRef{proxy.host}, proxy.port);
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index 5dba902e..f7140ab1 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -2904,4 +2904,193 @@ StringRef strproto(shrpx_proto proto) {
   assert(0);
 }
 
+// Configures the following member in |config|: router,
+// conn.downstream.addr_groups, wildcard_patterns,
+int configure_downstream_group(Config *config, bool http2_proxy,
+                               bool numeric_addr_only,
+                               const TLSConfig &tlsconf) {
+  auto &downstreamconf = config->conn.downstream;
+  auto &addr_groups = downstreamconf.addr_groups;
+
+  if (addr_groups.empty()) {
+    DownstreamAddrConfig addr{};
+    addr.host = ImmutableString::from_lit(DEFAULT_DOWNSTREAM_HOST);
+    addr.port = DEFAULT_DOWNSTREAM_PORT;
+    addr.proto = PROTO_HTTP1;
+
+    DownstreamAddrGroupConfig g(StringRef::from_lit("/"));
+    g.addrs.push_back(std::move(addr));
+    config->router.add_route(StringRef{g.pattern}, addr_groups.size());
+    addr_groups.push_back(std::move(g));
+  } else if (http2_proxy) {
+    // We don't support host mapping in these cases.  Move all
+    // non-catch-all patterns to catch-all pattern.
+    DownstreamAddrGroupConfig catch_all(StringRef::from_lit("/"));
+    for (auto &g : addr_groups) {
+      std::move(std::begin(g.addrs), std::end(g.addrs),
+                std::back_inserter(catch_all.addrs));
+    }
+    std::vector<DownstreamAddrGroupConfig>().swap(addr_groups);
+    std::vector<WildcardPattern>().swap(config->wildcard_patterns);
+    // maybe not necessary?
+    config->router = Router();
+    config->router.add_route(StringRef{catch_all.pattern}, addr_groups.size());
+    addr_groups.push_back(std::move(catch_all));
+  } else {
+    auto &wildcard_patterns = config->wildcard_patterns;
+    std::sort(std::begin(wildcard_patterns), std::end(wildcard_patterns),
+              [](const WildcardPattern &lhs, const WildcardPattern &rhs) {
+                return std::lexicographical_compare(
+                    rhs.host.rbegin(), rhs.host.rend(), lhs.host.rbegin(),
+                    lhs.host.rend());
+              });
+    if (LOG_ENABLED(INFO)) {
+      LOG(INFO) << "Reverse sorted wildcard hosts (compared from tail to head, "
+                   "and sorted in reverse order):";
+      for (auto &wp : config->wildcard_patterns) {
+        LOG(INFO) << wp.host;
+      }
+    }
+  }
+
+  // backward compatibility: override all SNI fields with the option
+  // value --backend-tls-sni-field
+  if (!tlsconf.backend_sni_name.empty()) {
+    auto &sni = tlsconf.backend_sni_name;
+    for (auto &addr_group : addr_groups) {
+      for (auto &addr : addr_group.addrs) {
+        addr.sni = sni;
+      }
+    }
+  }
+
+  if (LOG_ENABLED(INFO)) {
+    LOG(INFO) << "Resolving backend address";
+  }
+
+  ssize_t catch_all_group = -1;
+  for (size_t i = 0; i < addr_groups.size(); ++i) {
+    auto &g = addr_groups[i];
+    if (g.pattern == StringRef::from_lit("/")) {
+      catch_all_group = i;
+    }
+    if (LOG_ENABLED(INFO)) {
+      LOG(INFO) << "Host-path pattern: group " << i << ": '" << g.pattern
+                << "'";
+      for (auto &addr : g.addrs) {
+        LOG(INFO) << "group " << i << " -> " << addr.host.c_str()
+                  << (addr.host_unix ? "" : ":" + util::utos(addr.port))
+                  << ", proto=" << strproto(addr.proto)
+                  << (addr.tls ? ", tls" : "");
+      }
+    }
+  }
+
+  if (catch_all_group == -1) {
+    LOG(FATAL) << "backend: No catch-all backend address is configured";
+    return -1;
+  }
+
+  downstreamconf.addr_group_catch_all = catch_all_group;
+
+  if (LOG_ENABLED(INFO)) {
+    LOG(INFO) << "Catch-all pattern is group " << catch_all_group;
+  }
+
+  auto resolve_flags = numeric_addr_only ? AI_NUMERICHOST : 0;
+
+  for (auto &g : addr_groups) {
+    for (auto &addr : g.addrs) {
+
+      if (addr.host_unix) {
+        // for AF_UNIX socket, we use "localhost" as host for backend
+        // hostport.  This is used as Host header field to backend and
+        // not going to be passed to any syscalls.
+        addr.hostport = "localhost";
+
+        auto path = addr.host.c_str();
+        auto pathlen = addr.host.size();
+
+        if (pathlen + 1 > sizeof(addr.addr.su.un.sun_path)) {
+          LOG(FATAL) << "UNIX domain socket path " << path << " is too long > "
+                     << sizeof(addr.addr.su.un.sun_path);
+          return -1;
+        }
+
+        if (LOG_ENABLED(INFO)) {
+          LOG(INFO) << "Use UNIX domain socket path " << path
+                    << " for backend connection";
+        }
+
+        addr.addr.su.un.sun_family = AF_UNIX;
+        // copy path including terminal NULL
+        std::copy_n(path, pathlen + 1, addr.addr.su.un.sun_path);
+        addr.addr.len = sizeof(addr.addr.su.un);
+
+        continue;
+      }
+
+      addr.hostport = ImmutableString(
+          util::make_http_hostport(StringRef(addr.host), addr.port));
+
+      auto hostport = util::make_hostport(StringRef{addr.host}, addr.port);
+
+      if (resolve_hostname(&addr.addr, addr.host.c_str(), addr.port,
+                           downstreamconf.family, resolve_flags) == -1) {
+        LOG(FATAL) << "Resolving backend address failed: " << hostport;
+        return -1;
+      }
+      LOG(NOTICE) << "Resolved backend address: " << hostport << " -> "
+                  << util::to_numeric_addr(&addr.addr);
+    }
+  }
+
+  return 0;
+}
+
+int resolve_hostname(Address *addr, const char *hostname, uint16_t port,
+                     int family, int additional_flags) {
+  int rv;
+
+  auto service = util::utos(port);
+
+  addrinfo hints{};
+  hints.ai_family = family;
+  hints.ai_socktype = SOCK_STREAM;
+  hints.ai_flags |= additional_flags;
+#ifdef AI_ADDRCONFIG
+  hints.ai_flags |= AI_ADDRCONFIG;
+#endif // AI_ADDRCONFIG
+  addrinfo *res;
+
+  rv = getaddrinfo(hostname, service.c_str(), &hints, &res);
+  if (rv != 0) {
+    LOG(FATAL) << "Unable to resolve address for " << hostname << ": "
+               << gai_strerror(rv);
+    return -1;
+  }
+
+  auto res_d = defer(freeaddrinfo, res);
+
+  char host[NI_MAXHOST];
+  rv = getnameinfo(res->ai_addr, res->ai_addrlen, host, sizeof(host), nullptr,
+                   0, NI_NUMERICHOST);
+  if (rv != 0) {
+    LOG(FATAL) << "Address resolution for " << hostname
+               << " failed: " << gai_strerror(rv);
+
+    return -1;
+  }
+
+  if (LOG_ENABLED(INFO)) {
+    LOG(INFO) << "Address resolution for " << hostname
+              << " succeeded: " << host;
+  }
+
+  memcpy(&addr->su, res->ai_addr, res->ai_addrlen);
+  addr->len = res->ai_addrlen;
+
+  return 0;
+}
+
 } // namespace shrpx
diff --git a/src/shrpx_config.h b/src/shrpx_config.h
index 477fa95e..605949a5 100644
--- a/src/shrpx_config.h
+++ b/src/shrpx_config.h
@@ -283,6 +283,9 @@ constexpr auto SHRPX_OPT_BACKEND_HTTP2_SETTINGS_TIMEOUT =
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
+constexpr char DEFAULT_DOWNSTREAM_HOST[] = "127.0.0.1";
+constexpr int16_t DEFAULT_DOWNSTREAM_PORT = 80;
+
 enum shrpx_proto { PROTO_NONE, PROTO_HTTP1, PROTO_HTTP2, PROTO_MEMCACHED };
 
 enum shrpx_forwarded_param {
@@ -713,6 +716,13 @@ read_tls_ticket_key_file(const std::vector<std::string> &files,
 // Returns string representation of |proto|.
 StringRef strproto(shrpx_proto proto);
 
+int configure_downstream_group(Config *config, bool http2_proxy,
+                               bool numeric_addr_only,
+                               const TLSConfig &tlsconf);
+
+int resolve_hostname(Address *addr, const char *hostname, uint16_t port,
+                     int family, int additional_flags = 0);
+
 } // namespace shrpx
 
 #endif // SHRPX_CONFIG_H