The Omni Switch/Router Hardware Routing Engine (HRE-X)
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Each HRE-X routes up to 1.5 million packets per second. In an OmniS/R-9 with an HRE-X on
every switching module, for example, you could have up to 12 Mpps routed throughput. On
a per switch basis, the HRE-X also supports over 256,000 route entries and 64,000 Next Hop
destinations.

Valid HRE-X Configurations

You can configure an Omni Switch/Router chassis in one of two ways: with an HRE-X on
every single Omni Switch/Router switching module (distributed routing) or a single HRE-X on
the MPX (centralized routing).
Distributed Routing. In this configuration, you must install an HRE-X on every single switching
module in the chassis. In addition, you cannot install an HRE-X on the MPX. For example, in
an OmniS/R-9 with a single MPX, you would need eight (8) HRE-Xs for all the switching
modules. As a general rule, this configuration is recommended in networks of more than four
subnets from any one switch.
Centralized Routing. In this configuration, you must install the HRE-X on the MPX but not on
any Omni Switch/Router switching modules. The HRE-X will perform routing for all Omni
Switch/Router switching modules in the chassis. As a general rule, this configuration is recom-
mended for networks of two to four subnets from any one switch.

HRE-X Router Registers versus Feature Limitations

The HRE-X has three (3) registers that can be programmed with a MAC address and mask that
allows it to recognize which destination MAC addresses it should act as a router for. IP Rout-
ing, Virtual Router Redundancy Protocol (VRRP), ATM Classical IP (CIP), and Channelized DS3
(i.e., M013) utilize at least one of these registers for their operation. This leads to a restriction
of the combination of these features that can be supported on an Omni Switch/Router at any
given time.
♦ Important Note ♦
ATM and M013 are not supported in Release 4.5.
The HRE-X registers are programmed on a first come, first served basis. Any attempt to
program more than three registers fails. In current release, the order which these features
program the HRE-X is as follows:
1. ATM CIP
2. IP Routing (Note: If there is a second base MAC configured on the MPX, then it will also
take a second register.)
3. M013
4. VRRP
For example, if a switch has two base MACs and a CIP group, then no other features can be
configured. Any combination of the above features will work given the available HRE-X regis-
ters. IP routing always takes one register (two in the dual base MAC case), leaving the other
features to compete for the remaining two (one in the dual base MAC case). The other
features attempt to program a register only if they are enabled.
♦ Note ♦
ATM CIP is limited to 128 end node route cache entries.