Specifications

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12-4
Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, Release 5.0(3)U2(2)
OL-25782-02
Chapter 12 Managing the Unicast RIB and FIB
Managing the Unicast RIB and FIB
This example shows the FIB contents on a switch:
switch# show ip fib route
IPv4 routes for table default/base
------------------+------------------+---------------------
Prefix | Next-hop | Interface
------------------+------------------+---------------------
0.0.0.0/32 Drop Null0
255.255.255.255/32 Receive sup-eth1
Configuring Load Sharing in the Unicast FIB
Dynamic routing protocols, such as Open Shortest Path First (OSPF), support load balancing with
equal-cost multipath (ECMP). The routing protocol determines its best routes based on the metrics
configured for the protocol and installs up to the protocol-configured maximum paths in the unicast RIB.
The unicast RIB compares the administrative distances of all routing protocol paths in the RIB and
selects a best path set from all of the path sets installed by the routing protocols. The unicast RIB installs
this best path set into the FIB for use by the forwarding plane.
The forwarding plane uses a load-sharing algorithm to select one of the installed paths in the FIB to use
for a given data packet.
You can globally configure the following load-sharing settings:
• load-share mode—Selects the best path based on the destination address and port or the source and
the destination address and port.
• Universal ID—Sets the random seed for the hash algorithm. You do not need to configure the
Universal ID. Cisco NX-OS chooses the Universal ID if you do not configure it.
Note Load sharing uses the same path for all packets in a given flow. A flow is defined by the load-sharing
method that you configure. For example, if you configure source-destination load sharing, then all
packets with the same source IP address and destination IP address pair follow the same path.
To configure the unicast FIB load-sharing algorithm, use the following command in global configuration
mode:
show ip fib interfaces
Example:
switch# show ip fib interfaces
Displays the FIB interface information for IPv4.
show ip fib route
Example:
switch# show ip fib route
Displays the route table for IPv4.
show forwarding ipv4 route
Example:
switch# show forwarding ipv4 route
Displays the route table for IPv4.
Command Purpose