User's Manual

Tsunami MP.11 2454-R, 5054-R, and 5054-R-LR Installation and Management
Chapter 5. Using the Web Interface 45
Key Reasons to Use Routing Mode
One key reason why customers would use Routing mode is to implement virtual private networks (VPNs) or to let
nodes behind two different SUs communicate with each other. Many customers do this same thing in Bridging
mode by using secondary interfaces on the router at the BSU or virtual interfaces at the BSU in VLAN mode to
avoid some of the drawbacks of IP Routing mode.
Routing mode prevents the transport of non-IP protocols, which may be desirable for Service Providers
Routing mode is usually more efficient because Ethernet headers are not transported and non-IP traffic is
blocked.
Benefits of using Routing Mode
• Enabling RIP makes the unit easier to manage for a Service Provider that uses RIP to dynamically manage
routes. RIP is no longer very common for Service Providers or Enterprise customers and an implementation
of a more popular routing protocol like OSPF would be desirable.
• Routing mode saves bandwidth by not transporting non-IP protocols users might have enabled, like NetBEUI
or IPX/SPX, which eliminates the transmission of broadcasts and multicasts.
The MAC header is:
Destination MAC 6 bytes
Source MAC 6 bytes
Ethernet Type 2 bytes
If the average packet size is 1000 bytes, the overhead saved is 1.5%; With a frame size of 64 bytes, the
overhead saved is 20%; and for frame sizes of 128 bytes, the saving is 10%. Network researches claim that most
network traffic consists of frames smaller than 100 bytes.
In order to support routers behind the SUs with multiple subnets and prevent routing loops, you want individual
routes (and more then one) per SU.
Routing Mode Examples
In the first example, both the BSU and the SUs are configured for Routing mode. This example is appropriate for
businesses connecting remote offices that have different networks.
In example 2, the BSU is in Routing mode and the SUs are in Bridge mode. Notice the PCs behind the SUs must
configure their default gateways to point to the BSU, not the SU.