Data Sheet

System Manageability—Ethernet Controller I210
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10.5 SMBus Pass-Through Interface
SMBus is the system management bus defined by Intel. It is used in personal computers and servers
for low-speed system management communications. This section describes how the SMBus interface
operates in pass-through mode.
10.5.1 General
The SMBus sideband interface includes standard SMBus commands used for assigning a slave address
and gathering device information as well as Intel proprietary commands used specifically for the pass-
through interface.
10.5.2 Pass-Through Capabilities
This section details manageability capabilities the I210 provides while in SMBus mode. Pass-through
traffic is carried by the sideband interface as described in Section 10.1.
These services are not available in NC-SI mode.
When operating in SMBus mode, in addition to exposing a communication channel to the LAN for the
MC, the I210 provides the following manageability services to the MC:
• ARP handling — The I210 can be programmed to auto-ARP replying for ARP request packets to
reduce the traffic over the MC interconnect.
• Default configuration of filters by Flash - When working in SMBus mode, the default values of the
manageability receive filters can be set according to the PT LAN and flex TCO Flash structures.
• Padding of short packets. Packets smaller than 60 bytes but larger than 17 bytes will be padded to
a legal Ethernet packet.
• CRC calculation - The device adds an Ethernet CRC on all sent packets.
10.5.3 Automatic Ethernet ARP Operation
The I210 can offload the Ethernet Address Resolution Protocol (ARP) for the MC in order to reduce the
bandwidth required on the SMBus link.
Automatic Ethernet ARP parameters are loaded from the Flash when the I210 is powered up or
configured through the sideband management interface. The following parameters should be
configured in order to enable ARP operation:
• ARP auto-reply enabled
• ARP IP address (to filter ARP packets)
• ARP MAC addresses (for ARP responses)
These are all configurable over the sideband interface using the advanced version of the Receive Enable
command.
When an ARP request packet is received and ARP auto-reply is enabled, the I210 checks the targeted IP
address (after the packet has passed L2 checks and ARP checks). If the targeted IP matches the IP
configuration for the I210, it replies with an ARP response.
The I210 responds to ARP request targeted to the ARP IP address with the configured ARP MAC
address. If the I210 is not configured to do auto-ARP response, it can be configured to forward the ARP
packets to the MC (which can respond to ARP requests).