For Edge Cache to work, Exinda needs to be able to make an Internet connection to pull the web page being cached into its local cache, and it requires an IP address and access to the Internet to do this. This is accomplished through the management IP address, even if it is not located on the bridge that the traffic is going through.
The IP and default gateway can be configured in the IP Addresses page, by navigating to Configuration > System > Network. Even if the page is locally accessible, e.g., it has an IP address, it still might not have Internet access, if the users accessing the web UI (user interface) are in the same subnet, as they would not need a default gateway to communicate.
The DNS server can be configured in the DNS Page by navigating to Configuration > System > Network.