Merge pull request #1763 from porscheinformatik/annotation-filter-docs

Updated FAQ for usage of annotation-filter

docs/faq.md

@@ -272,6 +272,9 @@ an instance of a ingress controller. Let's assume you have two ingress controlle
 then you can start two ExternalDNS providers one with `--annotation-filter=kubernetes.io/ingress.class=nginx-internal`
 and one with `--annotation-filter=kubernetes.io/ingress.class=nginx-external`.
 
+Beware when using multiple sources, e.g. `--source=service --source=ingress`, `--annotation-filter` will filter every given source objects.
+If you need to filter only one specific source you have to run a separated external dns service containing only the wanted `--source`  and `--annotation-filter`.
+
 ### Can external-dns manage(add/remove) records in a hosted zone which is setup in different AWS account?
 
 Yes, give it the correct cross-account/assume-role permissions and use the `--aws-assume-role` flag https://github.com/kubernetes-sigs/external-dns/pull/524#issue-181256561