diff --git a/tools/genenv b/tools/genenv
index 95082ee542..5878a23aef 100755
--- a/tools/genenv
+++ b/tools/genenv
@@ -30,11 +30,11 @@ check_binarydependencies
 REAL_PATH=$(python -c "import os,sys;print os.path.realpath('$0')")
 cd "$(dirname "$REAL_PATH")/.."
 
-MY_IP=$(ip route get $(ip route | awk '$1 == "default" {print $3}') |
-    awk '$4 == "src" {print $5}')
+MY_IP=${MY_IP:-$(ip route get $(ip route | awk '$1 == "default" {print $3}') |
+    awk '$4 == "src" {print $5}')}
 
-MY_DEV=$(ip route get $(ip route | awk '$1 == "default" {print $3}') |
-    awk '$4 == "src" {print $3}')
+MY_DEV=${MY_DEV:-$(ip route get $(ip route | awk '$1 == "default" {print $3}') |
+    awk '$4 == "src" {print $3}')}
 
 echo MY_IP=$MY_IP
 echo MY_DEV=$MY_DEV