diff --git a/tests/instances.tcl b/tests/instances.tcl
index 0a0cbab12..3a4fadca0 100644
--- a/tests/instances.tcl
+++ b/tests/instances.tcl
@@ -25,6 +25,7 @@ set ::sentinel_instances {}
 set ::redis_instances {}
 set ::sentinel_base_port 20000
 set ::redis_base_port 30000
+set ::redis_port_count 1024
 set ::pids {} ; # We kill everything at exit
 set ::dirs {} ; # We remove all the temp dirs at exit
 set ::run_matching {} ; # If non empty, only tests matching pattern are run.
@@ -57,7 +58,7 @@ proc exec_instance {type cfgfile} {
 # Spawn a redis or sentinel instance, depending on 'type'.
 proc spawn_instance {type base_port count {conf {}}} {
     for {set j 0} {$j < $count} {incr j} {
-        set port [find_available_port $base_port]
+        set port [find_available_port $base_port $::redis_port_count]
         incr base_port
         puts "Starting $type #$j at port $port"
 
diff --git a/tests/support/server.tcl b/tests/support/server.tcl
index d086366dc..146ebc72c 100644
--- a/tests/support/server.tcl
+++ b/tests/support/server.tcl
@@ -214,14 +214,14 @@ proc start_server {options {code undefined}} {
     dict set config dir [tmpdir server]
 
     # start every server on a different port
-    set ::port [find_available_port [expr {$::port+1}]]
+    set port [find_available_port $::baseport $::portcount]
     if {$::tls} {
         dict set config "port" 0
-        dict set config "tls-port" $::port
+        dict set config "tls-port" $port
         dict set config "tls-cluster" "yes"
         dict set config "tls-replication" "yes"
     } else {
-        dict set config port $::port
+        dict set config port $port
     }
 
     set unixsocket [file normalize [format "%s/%s" [dict get $config "dir"] "socket"]]
@@ -243,10 +243,10 @@ proc start_server {options {code undefined}} {
     set server_started 0
     while {$server_started == 0} {
         if {$::verbose} {
-            puts -nonewline "=== ($tags) Starting server ${::host}:${::port} "
+            puts -nonewline "=== ($tags) Starting server ${::host}:${port} "
         }
 
-        send_data_packet $::test_server_fd "server-spawning" "port $::port"
+        send_data_packet $::test_server_fd "server-spawning" "port $port"
 
         if {$::valgrind} {
             set pid [exec valgrind --track-origins=yes --suppressions=src/valgrind.sup --show-reachable=no --show-possibly-lost=no --leak-check=full src/redis-server $config_file > $stdout 2> $stderr &]
@@ -291,19 +291,19 @@ proc start_server {options {code undefined}} {
         # for availability. Other test clients may grab the port before we
         # are able to do it for example.
         if {$port_busy} {
-            puts "Port $::port was already busy, trying another port..."
-            set ::port [find_available_port [expr {$::port+1}]]
+            puts "Port $port was already busy, trying another port..."
+            set port [find_available_port $::baseport $::portcount]
             if {$::tls} {
-                dict set config "tls-port" $::port
+                dict set config "tls-port" $port
             } else {
-                dict set config port $::port
+                dict set config port $port
             }
             create_server_config_file $config_file $config
             continue; # Try again
         }
 
         if {$code ne "undefined"} {
-            set serverisup [server_is_up $::host $::port $retrynum]
+            set serverisup [server_is_up $::host $port $retrynum]
         } else {
             set serverisup 1
         }
@@ -324,7 +324,6 @@ proc start_server {options {code undefined}} {
     # setup properties to be able to initialize a client object
     set port_param [expr $::tls ? {"tls-port"} : {"port"}]
     set host $::host
-    set port $::port
     if {[dict exists $config bind]} { set host [dict get $config bind] }
     if {[dict exists $config $port_param]} { set port [dict get $config $port_param] }
 
diff --git a/tests/support/util.tcl b/tests/support/util.tcl
index 7ecf5b79c..a5ded67a3 100644
--- a/tests/support/util.tcl
+++ b/tests/support/util.tcl
@@ -344,8 +344,8 @@ proc roundFloat f {
     format "%.10g" $f
 }
 
-proc find_available_port start {
-    for {set j $start} {$j < $start+1024} {incr j} {
+proc find_available_port {start count} {
+    for {set j $start} {$j < $start+$count} {incr j} {
         if {[catch {set fd1 [socket 127.0.0.1 $j]}] &&
             [catch {set fd2 [socket 127.0.0.1 [expr $j+10000]]}]} {
             return $j
@@ -356,8 +356,8 @@ proc find_available_port start {
             }
         }
     }
-    if {$j == $start+1024} {
-        error "Can't find a non busy port in the $start-[expr {$start+1023}] range."
+    if {$j == $start+$count} {
+        error "Can't find a non busy port in the $start-[expr {$start+$count-1}] range."
     }
 }
 
diff --git a/tests/test_helper.tcl b/tests/test_helper.tcl
index de0a64728..7fc0e6f00 100644
--- a/tests/test_helper.tcl
+++ b/tests/test_helper.tcl
@@ -70,7 +70,9 @@ set ::all_tests {
 set ::next_test 0
 
 set ::host 127.0.0.1
-set ::port 21111
+set ::port 6379; # port for external server
+set ::baseport 21111; # initial port for spawned redis servers
+set ::portcount 8000; # we don't wanna use more than 10000 to avoid collision with cluster bus ports
 set ::traceleaks 0
 set ::valgrind 0
 set ::tls 0
@@ -228,26 +230,26 @@ proc test_server_main {} {
     set tclsh [info nameofexecutable]
     # Open a listening socket, trying different ports in order to find a
     # non busy one.
-    set port [find_available_port 11111]
+    set clientport [find_available_port 11111 32]
     if {!$::quiet} {
-        puts "Starting test server at port $port"
+        puts "Starting test server at port $clientport"
     }
-    socket -server accept_test_clients  -myaddr 127.0.0.1 $port
+    socket -server accept_test_clients  -myaddr 127.0.0.1 $clientport
 
     # Start the client instances
     set ::clients_pids {}
     if {$::external} {
         set p [exec $tclsh [info script] {*}$::argv \
-            --client $port --port $::port &]
+            --client $clientport &]
         lappend ::clients_pids $p
     } else {
-        set start_port [expr {$::port+100}]
+        set start_port $::baseport
+        set port_count [expr {$::portcount / $::numclients}]
         for {set j 0} {$j < $::numclients} {incr j} {
-            set start_port [find_available_port $start_port]
             set p [exec $tclsh [info script] {*}$::argv \
-                --client $port --port $start_port &]
+                --client $clientport --baseport $start_port --portcount $port_count &]
             lappend ::clients_pids $p
-            incr start_port 10
+            incr start_port $port_count
         }
     }
 
@@ -510,6 +512,10 @@ proc print_help_screen {} {
         "--loop             Execute the specified set of tests forever."
         "--wait-server      Wait after server is started (so that you can attach a debugger)."
         "--tls              Run tests in TLS mode."
+        "--host <addr>      Run tests against an external host."
+        "--port <port>      TCP port to use against external host."
+        "--baseport <port>  Initial port number for spawned redis servers."
+        "--portcount <num>  Port range for spawned redis servers."
         "--help             Print this help screen."
     } "\n"]
 }
@@ -560,6 +566,12 @@ for {set j 0} {$j < [llength $argv]} {incr j} {
     } elseif {$opt eq {--port}} {
         set ::port $arg
         incr j
+    } elseif {$opt eq {--baseport}} {
+        set ::baseport $arg
+        incr j
+    } elseif {$opt eq {--portcount}} {
+        set ::portcount $arg
+        incr j
     } elseif {$opt eq {--accurate}} {
         set ::accurate 1
     } elseif {$opt eq {--force-failure}} {
diff --git a/tests/unit/other.tcl b/tests/unit/other.tcl
index 7720c055a..20a32e795 100644
--- a/tests/unit/other.tcl
+++ b/tests/unit/other.tcl
@@ -167,9 +167,9 @@ start_server {tags {"other"}} {
     tags {protocol} {
         test {PIPELINING stresser (also a regression for the old epoll bug)} {
             if {$::tls} {
-                set fd2 [::tls::socket $::host $::port]
+                set fd2 [::tls::socket [srv host] [srv port]]
             } else {
-                set fd2 [socket $::host $::port]
+                set fd2 [socket [srv host] [srv port]]
             }
             fconfigure $fd2 -encoding binary -translation binary
             puts -nonewline $fd2 "SELECT 9\r\n"