Added keepalived ipv6 configuration

content/u/blog/how-to-enable-ipv6-in-applications/contents.lr

@@ -112,6 +112,36 @@ localhost use `-h ::1`, to be globally reachable use `-h ::`.
 % lektor serve -h ::
 ```
 
+## How to use IPv6 in keepalived
+
+[Keepalived](https://keepalived.org/), the VRRP daemon for Linux,
+supports IPv6 for a while. However newer versions (wikipedia: citation
+needed) of keepalived require to have two different instances, if you
+are running dual stack VRRP messages. So your keepalived.conf for use
+with IPv6 might look as follows:
+
+```
+vrrp_instance router_internal {
+    state BACKUP
+    interface bond0.10
+    virtual_router_id 1
+
+    virtual_ipaddress {
+        2a0a:e5c0:2:0::7/64  dev bond0.10
+    }
+}
+
+vrrp_instance router_internal_ipv4 {
+    state BACKUP
+    interface bond0.10
+    virtual_router_id 2
+
+    virtual_ipaddress {
+        10.3.0.7/22 dev bond0.10
+    }
+}
+```
+
 ## How to enable IPv6 in Redhat Linux
 
 While Red Hat is not specifically an application, we still wanted