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page -38 OmniSwitch Troubleshooting Guide September 2005
Unknown L3 DA
The Coronado ASIC
• The FIFO logic maintains queues of frames from both Xybus interfaces and selects an incoming frame
for HRE processing. This FIFO is done on the on chip memory of the HRE.
• The parser logic selects fields from the frame to identify the protocol and find key values that are used
by the HRE for lookups (DA, SA)
• Coronado does a L2 SA pCAM lookup.
• Coronado determines this is a known source and retrieves Group ID.
• Coronado checks for special L2 DA (ARP,STP,IGMP,IPMS,Router)
• This lookup matches a Router, therefore routing is needed.
• Coronado performs L3 DA address lookup.
• This lookup fails and the packet is requeued to the software on the Sparc. (Slow path)
• The L3 DA is compared to the L3 FDB (routing table).
• If this lookup fails, the packet is sent to the default gateway.
• Which ever route the packet matches, the Coronado retrieves the Next Hop Router Cache (NHRC)
Index for this packet.
• The Coronado uses this index, to look up the NHRC and retrieve the QID and PDI.
• The L3 DA table in the pCAM is updated accordingly with this information.
• The frame is output from the Coronado into the Nantucket switching fabric via the FBUS.