Design Reference

Figure 44: Traditional routing after moving VMs
Optimized data center routing of VMs:
Two features make a data center optimized:
• VLAN routers in the Layer 2 domain (green icons)
• VRRP BackupMaster
The VLAN routers use lookup tables to determine the best path to route incoming traffic (red
dots) to the destination VM.
VRRP BackupMaster solves the problem of traffic congestion on the IST. Because there can
be only one VRRP Master, all other interfaces are in backup mode. In this case, all traffic is
forwarded over the IST link towards the primary VRRP switch. All traffic that arrives at the
VRRP backup interface is forwarded, so there is not enough bandwidth on the IST link to carry
all the aggregated riser traffic. VRRP BackupMaster overcomes this issue by ensuring that the
IST trunk is not used in such a case for primary data forwarding. The VRRP BackupMaster
acts as an IP router for packets destined for the logical VRRP IP address. All traffic is directly
routed to the destined subnetwork and not through Layer 2 switches to the VRRP Master. This
avoids potential limitation in the available IST bandwidth.
The following figure shows a solution that optimizes your network for bidirectional traffic flows.
However, this solution turns two SPBM BCB nodes into BEBs where MAC and ARP learning
will be enabled on the Inter-VSN routing interfaces. If you do not care about top-down traffic
flows, you can omit the Inter-VSN routing interfaces on the SPBM BCB nodes. This makes the
IP routed paths top-down less optimal, but the BCBs remain pure BCBs, thus simplifying core
switch configurations.
Distributed vRouting — Optimized (pre VM move):
SPBM design guidelines
94 Network Design Reference for Avaya VSP 4000 February 2014
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