diff --git a/doc/demo.sh b/doc/demo.sh
index 6a3cb19..5aed7f0 100755
--- a/doc/demo.sh
+++ b/doc/demo.sh
@@ -79,4 +79,10 @@ ip netns exec passt ethtool -K veth_passt tx off
 ip netns exec passt sysctl -w net.ipv4.ping_group_range="0 2147483647"
 
 
+sysctl -w net.core.rmem_max=16777216
+sysctl -w net.core.wmem_max=16777216
+sysctl -w net.core.rmem_default=16777216
+sysctl -w net.core.wmem_default=16777216
+
+
 ip netns exec passt ./passt