Specifications

HP Virtual Connect for Cisco Network Administrators (version 1.2x) page 28
using different vNets for the same VLAN, an administrator can control traffic flow on a per server NIC
basis. Below are some examples.
Advanced VC-Enet Designs: Example Design #1
Referring to Figure 12, an administrator could use one vNet (VC_LAN_1_A) to couple a NIC on Server
1 and a NIC on Server 2 with a VC uplink that is connected to an external switch port assigned to
VLAN 1. In this case, VC_LAN_1_A represents VLAN 1 within the VC Domain. Both Server 1 and
Server 2 can talk directly with each other within VC_LAN_1_A, without leaving the VC Domain, and
both servers can talk to devices on VLAN 1 via the active VC uplink port. In addition, an
administrator could create another vNet (VC_LAN_1_B) and assign Server 3 to it. Virtual Connect
does not allow Server 3’s NIC port to directly communicate with any other NIC port within this VC
Domain since there are no other NIC ports assigned to VC_LAN_1_B. VC_LAN_1_B also represents
VLAN 1 within the VC Domain. Server 3 effectively has its own dedicated VC uplinks to reach VLAN
1. If the external switched network permits it, Server 3 can communicate with Server 1 and 2 by
exiting the VC Domain via the active uplink for VC_LAN_1_B, transiting the external Cisco switch,
and reentering the VC Domain on the active uplink for VC_LAN_1_A.
Figure 11. VC Domain Showing Various Uses of vNets
(see Appendix A for a description of the elements in the above diagram)
Advanced VC-Enet Designs: Example Design #2
Another example of an advanced configuration using vNets is depicted in the figure below. In
diagram below, blade servers 1 thru 3 need to be connected to the external network with a 4 Gb
pipe. However, ports from different VC modules need to be used to eliminate single points of failure
(redundant VC modules). If two uplink ports from module 1 and two uplink ports from module 2 are
assigned to the same vNet, then VC forms two port channels (two logical paths). As was discussed
in the section entitled ‘VC Uplink Load Balancing”, VC must prevent loops on the network so only
one logical path will be active at a time. This means the server’s bandwidth is reduced from 4 Gb to
2 Gb since one whole channel is placed in standby mode.
To solve this problem, two vNets are used instead of one. Each vNet is assigned the uplink ports for a
single port channel. Since each vNet only has a single port channel, there is only one logical path