III. CAPÍTULO II: MARCO CONCEPTUAL 30
3.3 conceptos centrales musicales 33
At this point in the process, you can start to consider implementation details, reviewing each of the logical networks that you identified during the earlier parts of the process to decide where (i.e., in which physical location) they need to be deployed and to determine the set of network sites, IP pools, and MAC address pools needed to make the networks available and used in those locations.
Physical locations and host servers
It makes sense to make some logical networks available in all physical locations. Many of the cloud infrastructure networks, such as management, storage, and live migration, clearly are relevant to and should be made available everywhere while the availability of others should be restricted to specified locations. If your organization’s development team is located in a single location, it might be reasonable to ensure that the logical network you create for development workloads would be available only on servers in that location.
Having identified the physical locations on which a given logical network will be available, the next decision point is which of the Hyper-V hosts in that location should be configured to support it. Again, it makes sense that some of the logical networks should be made available on all of the host computers in that location, the logical networks you define for cloud infrastructure such as Management and Storage clearly being the most obvious candidates, though there may well be exceptions to this general rule. For example, not all servers will have access to network attached storage.
Servers may have been set aside for specific workloads or projects or allocated (dedicated) to specific tenants, and in these cases, you should ensure that the logical network that will carry those workloads is available only on those computers. To achieve this, you first need to define host groups. The recommend approach is to create a parent host group (for example Production as shown in Figure 2-27) that clearly identifies the group of dedicated servers and child host groups for each physical site where those servers will be located; Reading and Seattle in Figure 2-27, for example.
FIGURE 2-27 Creating host groups for dedicated servers.
Network adapters in Windows Server 2012 Hyper-V servers can be associated with multiple logical networks. However, there is no internal routing between them. If you want to allow virtual machines and host services configured on one logical network to communicate with those on another, you will need to deploy a router or gateway device.
Network sites (logical network definitions)
Network sites, otherwise known as logical network definitions, are used to define the VLANs and IP subnets that are to be associated with the logical network in each physical location. However, it is unnecessary to define network sites for all of your logical networks. The following key points replicated from the Configuring Logical Networking in VMM Overview section of the VMM documentation (available at http://technet.microsoft.com/en-
us/library/jj721568.aspx) set out the guidelines that will help you determine whether you need to define a network site for the logical network in a given physical location:
If you want to use DHCP that is already available on the network, and you are not using VLANs, you do not have to create any network sites but as a recommended best practice, you should always aim to do so.
If using VM networks that use Network Virtualization, you must create at least one network site and associate at least one IP subnet with the site as mentioned earlier. You can also assign a VLAN to the network site, as appropriate. Creating a network site with an IP subnet makes it possible to create an IP address pool for the logical network, which is necessary for Network Virtualization.If the VM networks you create will not use Network Virtualization as an isolation mechanism, the following guidance applies:
If you plan to use a load balancer that is managed by VMM to load-balance a service tier, create at least one network site and associate at least one IP subnet with the
If you want to create static IP address pools that VMM manages, create at least one network site and associate at least one IP subnet with the network site.
If you want to use Dynamic Host Configuration Protocol (DHCP) that is already available on the network to assign IP addresses to virtual devices in a specified VLAN, create network sites with only VLANs assigned to them. With that said, it is strongly recommended that you fill in all the network properties in VMM, even if you’re not going to use VMM for IP address assignment and management.IP address pools
If you associate one or more IP subnets with a network site, you can also create static IP address pools for those subnets. Static IP address pools make it possible for VMM to automatically allocate static IP addresses to Windows-based VMs that are running on any managed Hyper-V, VMware ESX, or Citrix XenServer host. VMM can automatically assign static IP addresses from the pool to stand-alone virtual machines, to virtual machines that are deployed as part of a service, and to physical computers when you use VMM to deploy them as Hyper-V hosts. Additionally, when you create a static IP address pool, you can define a reserved range of IP addresses that can be assigned to load balancers as virtual IP addresses. VMM automatically assigns a virtual IP address to a load balancer during the deployment of a load-balanced service tier.
As with network sites, it is unnecessary to define IP address pools for all of your network sites. The following key points replicated from the VMM documentation at
http://technet.microsoft.com/en-us/library/jj721568.aspx set out the guidelines that will help you determine whether you need to do so:
If your network configuration includes VM networks that use Network Virtualization, you must create IP address pools on both the logical network that provides the foundation for those VM networks, and on the VM networks themselves. If the virtual machines on the VM networks are configured to use DHCP, VMM will respond to the DHCP request with an address from an IP address pool.
VLAN-based configuration: If you are using a VLAN-based network configuration, you can use either DHCP, if it is available, and/or IP address pools. To use IP address pools, create them on the logical network. They will automatically become available on the VM network.
VM network that gives direct access to the logical network (“no isolation”): If you have a VM network that gives direct access to the underlying logical network, you can use either DHCP, if it is available, and/or IP address pools for that network. To use IP address pools, create them on the logical network. They will automatically become available on the VM network.
If you are using external networks that are implemented through a vendor network- management console (in other words, if you will use a virtual switch extension manager), your IP address pools will be imported from the vendor network- management database. Therefore, do not create IP address pools in VMM.MAC address pools
If a VM connected to the logical network will obtain IP addresses from a static IP address pool, you must also configure the VM to use a static MAC address. You can either specify the MAC address manually or have VMM automatically assign a MAC address from either a central MAC address pool or one that you have created for a specific network site.