CEF load sharing details (Cisco IOS hints and tricks)
For every CEF entry (IP route) where there are multiple paths to the destination, the router creates a 16-row hash table, populating the entries with pointers to individual paths. The hash table can be inspected with the show ip cef prefix internal command.
The load balancing ratio is approxiated by number of entries in the hash table belonging to each path. If you have unequal-cost load balancing (EIGRP based on composite metrics and MPLS TE tunnels based on requested bandwidth), individual paths will be associated with different number of rows.
If you configure per-destination load balancing, the source and destination IP address in the incoming IP packet are hashed into a 4-bit value that selects the outgoing path in the CEF has table.
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