82598EB Datasheet, PDF (469/596 Pages) Intel Corporation – Intel® 82598EB 10 Gigabit Ethernet Controller Datasheet

Intel^® 82598EB 10 GbE Controller - SMBus Troubleshooting Guide
5.3.12.5.2 Management Control Register (MANC 0x5820)
This register indicates which filters are enabled. It is possible to configure all of the filters yet not
enable them, in which case, no management traffic is routed to the BMC. Or, the BMC might be
receiving undesired traffic, such as ARP requests when the 82598EB was configured to do automatic
ARP responses.
Check this register if getting unwanted traffic or if packets aren’t getting sent to the BMC.
Bit 17 (Receive TCO Packets Enable) must also be set in order for any packets are sent to a BMC. Note
that it doesn’t matter what the other enabled filters are, if this one is off, no packets are sent to the
BMC.
Bit 21 (Enable Management-to-Host) enables or disables the various filters that also allow
manageability traffic (all those that pass the filters in the 82598EB) to optionally be passed to the OS.
5.3.12.5.3 Management Control To Host Register (MANC2H 0x5860)
The 82598EB has a large number of filtering mechanisms by which network traffic can be directed to a
BMC. Traffic sent to the BMC is typically not sent to the host OS as well. For example, the OS is not
interested in RMCP/RMCP+ traffic. However, the OS might be interested in ARP requests. If the
82598EB is configured for automatic ARP requests, this means that a filter for ARP requests has been
configured and enabled, if the ARP request matches that of the BMC, then that ARP request is not sent
to the OS unless specifically configured to do so. This is what the MANC2H register shows, which
manageability filters to also pass the data up to the OS as well as the BMC.
Using the ARP request example; typically it is desirable to allow the OS to receive these, as such, bit 7
(ARP Request) should be set.
5.3.12.6 Unable to Transmit Packets from the BMC
If the BMC has been transmitting and receiving data without issue for a period of time and then begins
to receive NACKs from the 82598EB when it attempts to write a packet, the problem is most likely due
to the fact that the buffers internal to the 82598EB are full of data that has been received from the
network; however, has yet to be read by the BMC.
Being an embedded device, the 82598EB has limited buffers, which it shares for receiving and
transmitting data. If a BMC does not keep the incoming data read, the 82598EB can be filled up, which
does not allow the BMC to transmit anymore data, resulting in NACKs.
If this situation occurs, the recommended solution is to have the BMC issue a Receive Enable command
to disable anymore incoming data, go read all the data from the 82598EB and then use the Receive
Enable command to enable incoming data once again.
5.3.12.7 SMBus Fragment Size
The SMBus specification indicates a maximum SMBus transaction size of 32 bytes. Most of the data
passed between the 82598EB and the BMC over the SMBus is RMCP/RMCP+ traffic, which by its very
nature (UDP traffic) is significantly larger than 32 bytes in length, thus requiring multiple SMBus
transactions to move a packet from the 82598EB to the BMC or to send a packet from the BMC to the
82598EB.
Recognizing this bottleneck, the 82598EB can handle up to 240 bytes of data within a single
transaction. This is a configurable setting within the EEPROM.
The default value in the EEPROM images is 32, per the SMBus specification. If performance is an issue,
it is recommended that you increase this size.
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