diff --git a/test/functional/test_framework/netutil.py b/test/functional/test_framework/netutil.py
index 08d41fe97f..75fff2079d 100644
--- a/test/functional/test_framework/netutil.py
+++ b/test/functional/test_framework/netutil.py
@@ -13,6 +13,10 @@ import struct
 import array
 import os
 
+# Easily unreachable address. Attempts to connect to it will stay within the machine.
+# Used to avoid non-loopback traffic or DNS queries.
+UNREACHABLE_PROXY_ARG = '-proxy=127.0.0.1:1'
+
 # STATE_ESTABLISHED = '01'
 # STATE_SYN_SENT  = '02'
 # STATE_SYN_RECV = '03'