Disable ipv6 on frr instance

Related-Prod: PRODX-12019
Change-Id: Iccfd996bb643a4979e07ed8a0f195a4c24b5c171
diff --git a/de/heat-templates/scripts/instance_boot.sh b/de/heat-templates/scripts/instance_boot.sh
index 772ecdf..acc90f2 100644
--- a/de/heat-templates/scripts/instance_boot.sh
+++ b/de/heat-templates/scripts/instance_boot.sh
@@ -675,6 +675,15 @@
 
 }
 
+function disable_ipv6 {
+    cat << EOF > /etc/sysctl.d/11-ipv6-disable.conf
+net.ipv6.conf.all.disable_ipv6 = 1
+net.ipv6.conf.default.disable_ipv6 = 1
+net.ipv6.conf.lo.disable_ipv6 = 1
+EOF
+    sysctl -p /etc/sysctl.d/11-ipv6-disable.conf
+}
+
 function setup_evpn {
 
 cat << EOF > /etc/netplan/60-evpn.yaml
@@ -783,6 +792,7 @@
 
     systemctl restart frr
 
+    disable_ipv6
     setup_evpn
 }