The physical network is implemented with Gigabit Ethernet switches. Prevalently they are HP ProCurve 2810, slowly being replaced by HP ProCurve 2530 in some cases.
For traffic separation we leverage VLANs and provide physical servers with a dedicated link for each VLAN that it needs access to.
Routers are attached to upstream ports provided by the data center, a dedicated management link, and a link with tagged VLANs for everything else.
The following VLANs and logical networks are in use:
MGM - Management, purely for administrative purposes. This VLAN connects switch management ports, Remote Access Controllers, and typically provides a separate point of entry so that administrator can use management features even in the case that the routers are completely offline. Not accessible from the outside world, private IPv4 address space. DNS example: switch.mgm.rzob.gocept.net.
FE - Frontend, for providing actual service traffic. This VLAN connects to machines that provide customers’ applications to the public. This network is switched to the virtual machines and leverages completely public traffic. The DC firewalls to not filter this. Customer applications are free to use any ports they like but must be careful opening them. VMs can filter this network locally. All VMs receive a NIC on this VLAN but not necessarily IPv4 addresses if they do not provide public traffic. DNS example: vm00.fe.rzob.gocept.net.
SRV - Server to server communication. Used for customer application components to talk to each other, e.g. database traffic and for management purposes on the application level. This network is firewalled from the DC firewalls and allows only HTTP/S and SSH traffic. Additionally VMs can filter this traffic locally and only allow free traffic by default from VMs belonging to the same project. All VMs have this NIC used and addresses allocated. DNS example: vm00.srv.rzob.gocept.net or simply vm00.gocept.net.
STO - Storage communication. Used by the virtualization and backup servers to access the network storages where the VM disk images are located. DNS example: filer.sto.rzob.gocept.net.
STB - Storage backend communication. Used by the storage layer for replication and self-management. DNS example: filer.stb.rzob.gocept.net.
Individual VMs that run management services, like monitoring, may get bridged into the additional VLANs as necessary.
The routers suppress routing of IP networks on VLANs not belonging there.
Services that require tight control are bound to listening IP addresses on only those networks but then can get relaxed ACL rules making configuration simpler and easier to understand.
Your application is generally free to use any open port on a machine above 1024. Especially if you run a component that has a registered, well-known port, please use that.
However, custom applications may run into the trouble of colliding with other components. For that we guarantee that the ports 61000-61999 will never be used by our managed components, nor by the kernel when assigning dynamic ports.