Added .adoc to the xref.

Signed-off-by: John Wilkins <jowilkin@redhat.com>

Author: johnwilkins

installing/installing_bare_metal_ipi/ipi-install-prerequisites.adoc

@@ -42,7 +42,7 @@ include::modules/ipi-install-network-requirements.adoc[leveloffset=+1]
 [role="_additional-resources"]
 .Additional resources
 
-* xref:../../networking/dns-operator#nw-dns-forward_dns-operator[Using DNS forwarding]
+* xref:../../networking/dns-operator.adoc#nw-dns-forward_dns-operator[Using DNS forwarding]
 
 include::modules/ipi-install-configuring-nodes.adoc[leveloffset=+1]