The separation between network configuration and network hardware configuration introduces the same flexibility to other types of link configurations. For example, virtual local area networks (VLANs), link aggregations, and IP tunnels can be assigned administratively-chosen names and then configured by referring to those names. Other related tasks, such as performing dynamic reconfiguration (DR) to replace hardware devices, are also easier to perform because no further network reconfiguration is required, provided that the network configuration was not deleted.
The following figure shows the interrelationship among devices, link types, and their corresponding interfaces.
The figure also provides a sample of how administratively chosen names can be used in the network setup;
The device instances ce0 and qfe3 are designated to service traffic for IT Operations, and hence given the link names subitops0 and subitops1. The customized names facilitate the identification of the roles of these links.
VLANs are configured on the subitops0 link. These VLANs, in turn, are also assigned customized names, such as sales1 and sales2. The VLAN sales2's IP interface is plumbed and operational.
The device instances qfe0 and qfe2 are used to service video traffic. Accordingly, the corresponding links in the data-link layer are assigned the names subvideo0 and subvideo1. These two links are aggregated to host video feed. The link aggregation possesses its own customized name as well, video0.
Two interfaces (subitops0 and subitops1) with different underlying hardware (ce and qfe) are grouped together as an IPMP group (itops0) to host email traffic.
Although IPMP interfaces are not links on the data-link layer, these interfaces, like the links, can also be assigned customized names. For more information about IPMP groups, see Chapter 7, Introducing IPMP.
Two interfaces have no underlying devices: the tunnel vpn1, which is configured for VPN connections and lo0 for IP loopback operations.
All of the link and interface configurations in this figure are independent of the configurations in the underlying hardware. For example, if the qfe card is replaced, the video0 interface configuration for video traffic remains and can later be applied to a replacement NIC.