Configuration MP.11-R Installation and Management
System Parameters
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The use of Routing mode requires more attention to the configuration of the unit and thorough planning of the network
topology of your outdoor network. The unit can use Routing mode in any combination of BSU and SUs. For example, you
may have the BSU in Routing mode and the SU in Bridge mode, or vice versa.
When using Routing mode, pay close attention to the configuration of the default gateway both on your unit and on your
PCs and servers. The default gateway controls where packets with unknown destinations (Internet) should be sent. Be
sure that each device is configured with the correct default gateway for the next hop router. Usually this is the next router
on the way to your connection to the Internet. You can configure routes to other networks on your Intranet through the
addition of static routes in your router’s routing table.
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
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 than 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.
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