diff --git a/vpnsetup.sh b/vpnsetup.sh
index d61db85..c6335be 100755
--- a/vpnsetup.sh
+++ b/vpnsetup.sh
@@ -335,30 +335,32 @@ bigecho "Updating sysctl settings..."
 
 if ! grep -qs "hwdsl2 VPN script" /etc/sysctl.conf; then
   conf_bk "/etc/sysctl.conf"
+  if [ "$(getconf LONG_BIT)" = "64" ]; then
+    SHM_MAX=68719476736
+    SHM_ALL=4294967296
+  else
+    SHM_MAX=4294967295
+    SHM_ALL=268435456
+  fi
 cat >> /etc/sysctl.conf <<EOF
 
 # Added by hwdsl2 VPN script
 kernel.msgmnb = 65536
 kernel.msgmax = 65536
-kernel.shmmax = 68719476736
-kernel.shmall = 4294967296
+kernel.shmmax = $SHM_MAX
+kernel.shmall = $SHM_ALL
 
 net.ipv4.ip_forward = 1
-net.ipv4.tcp_syncookies = 1
 net.ipv4.conf.all.accept_source_route = 0
-net.ipv4.conf.default.accept_source_route = 0
 net.ipv4.conf.all.accept_redirects = 0
-net.ipv4.conf.default.accept_redirects = 0
 net.ipv4.conf.all.send_redirects = 0
-net.ipv4.conf.default.send_redirects = 0
-net.ipv4.conf.lo.send_redirects = 0
-net.ipv4.conf.$NET_IFACE.send_redirects = 0
 net.ipv4.conf.all.rp_filter = 0
+net.ipv4.conf.default.accept_source_route = 0
+net.ipv4.conf.default.accept_redirects = 0
+net.ipv4.conf.default.send_redirects = 0
 net.ipv4.conf.default.rp_filter = 0
-net.ipv4.conf.lo.rp_filter = 0
+net.ipv4.conf.$NET_IFACE.send_redirects = 0
 net.ipv4.conf.$NET_IFACE.rp_filter = 0
-net.ipv4.icmp_echo_ignore_broadcasts = 1
-net.ipv4.icmp_ignore_bogus_error_responses = 1
 
 net.core.wmem_max = 12582912
 net.core.rmem_max = 12582912
diff --git a/vpnsetup_centos.sh b/vpnsetup_centos.sh
index bfa11a4..43b4f92 100755
--- a/vpnsetup_centos.sh
+++ b/vpnsetup_centos.sh
@@ -321,30 +321,32 @@ bigecho "Updating sysctl settings..."
 
 if ! grep -qs "hwdsl2 VPN script" /etc/sysctl.conf; then
   conf_bk "/etc/sysctl.conf"
+  if [ "$(getconf LONG_BIT)" = "64" ]; then
+    SHM_MAX=68719476736
+    SHM_ALL=4294967296
+  else
+    SHM_MAX=4294967295
+    SHM_ALL=268435456
+  fi
 cat >> /etc/sysctl.conf <<EOF
 
 # Added by hwdsl2 VPN script
 kernel.msgmnb = 65536
 kernel.msgmax = 65536
-kernel.shmmax = 68719476736
-kernel.shmall = 4294967296
+kernel.shmmax = $SHM_MAX
+kernel.shmall = $SHM_ALL
 
 net.ipv4.ip_forward = 1
-net.ipv4.tcp_syncookies = 1
 net.ipv4.conf.all.accept_source_route = 0
-net.ipv4.conf.default.accept_source_route = 0
 net.ipv4.conf.all.accept_redirects = 0
-net.ipv4.conf.default.accept_redirects = 0
 net.ipv4.conf.all.send_redirects = 0
-net.ipv4.conf.default.send_redirects = 0
-net.ipv4.conf.lo.send_redirects = 0
-net.ipv4.conf.$NET_IFACE.send_redirects = 0
 net.ipv4.conf.all.rp_filter = 0
+net.ipv4.conf.default.accept_source_route = 0
+net.ipv4.conf.default.accept_redirects = 0
+net.ipv4.conf.default.send_redirects = 0
 net.ipv4.conf.default.rp_filter = 0
-net.ipv4.conf.lo.rp_filter = 0
+net.ipv4.conf.$NET_IFACE.send_redirects = 0
 net.ipv4.conf.$NET_IFACE.rp_filter = 0
-net.ipv4.icmp_echo_ignore_broadcasts = 1
-net.ipv4.icmp_ignore_bogus_error_responses = 1
 
 net.core.wmem_max = 12582912
 net.core.rmem_max = 12582912