Hi I trying to replace your Apache Httpd with mod_cluster load balancer with Undertow frontend modcluster as part of Wildfly 9.0.1. It works fine when I define a 'real' IP address defined in /etc/hosts: 127.0.0.1 localhost 10.22.62.40 mdzhrnesir01.standard.six-group.net mdzhrnesir01 But this IP address 10.22.62.117 is not taken by untertow: ip addr . 8: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP link/ether 00:17:a4:77:f0:b6 brd ff:ff:ff:ff:ff:ff inet 10.22.62.40/24 brd 10.22.62.255 scope global bond0 inet 10.22.62.117/24 scope global secondary bond0 I also faced to problem, that running the example presented by Stuart Douglas doesn't work inside a docker container. Even I execute step by step. Without digging into the source code, what are the criteria under which Undertow frontend modcluster accepts IP address(es)? Do you also have a proposal for configuring Undertow modcluster to listen to two interfaces? Say an internal IP address and an virtual external IP address? I think with Apache, we defined 0.0.0.0 and then Apache with mod_cluster was listening on all interfaces, if I remember correctly. Thanks a lot in advance Ralf