Split Horizon; Virtualization Support; Graceful Restart And High Availability - Cisco Nexus 7000 Series Configuration Manual

Chapter 8 Configuring EIGRP
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m .
EIGRP in Cisco NX-OS does not support unequal cost load balancing.
Note

Split Horizon

You can use split horizon to ensure that EIGRP never advertises a route out of the interface where it was
learned.
Split horizon is a method that controls the sending of EIGRP update and query packets. When you enable
split horizon on an interface, Cisco NX-OS does not send update and query packets for destinations that
were learned from this interface. Controlling update and query packets in this manner reduces the
possibility of routing loops.
Split horizon with poison reverse configures EIGRP to advertise a learned route as unreachable back
through that the interface that EIGRP learned the route from.
EIGRP uses split horizon or split horizon with poison reverse in the following scenarios:
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•
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By default, the split horizon feature is enabled on all interfaces.

Virtualization Support

Cisco NX-OS supports multiple instances of the EIGRP protocol that runs on the same system. EIGRP
supports Virtual Routing and Forwarding instances (VRFs). VRFs exist within virtual device contexts
(VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you
specifically configure another VDC and VRF. See the Cisco Nexus 7000 Series NX-OS Virtual Device
Context Configuration Guide, Release 4.x and
By default, every instance uses the same system router ID. You can optionally configure a unique router
ID for each instance.

Graceful Restart and High Availability

Cisco NX-OS supports nonstop forwarding and graceful restart for EIGRP.
You can use nonstop forwarding for EIGRP to forward data packets along known routes in the FIB while
the EIGRP routing protocol information is being restored following a failover. With NSF, peer
networking devices do not experience routing flaps. During failover, data traffic is forwarded through
intelligent modules while the standby supervisor becomes active.
If a Cisco NX-OS system experiences a cold reboot, network does not forward traffic to the system and
removes the system from the network topology. In this scenario, EIGRP experiences a stateless restart,
and all neighbors are removed. Cisco NX-OS applies the startup configuration, and EIGRP rediscovers
the neighbors and shares the full EIGRP routing information again.
A dual supervisor platform that runs Cisco NX-OS can experience a stateful supervisor switchover.
Before the switchover occurs, EIGRP uses a graceful restart to announce that EIGRP will be unavailable
for some time. During a switchover, EIGRP uses nonstop forwarding to continue forwarding traffic
based on the information in the FIB, and the system is not taken out of the network topology.
OL-20002-02
Exchanging topology tables for the first time between two routers in startup mode.
Advertising a topology table change.
Sending a Query message.
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
Chapter 14, "Configuring Layer 3 Virtualization."
Information About EIGRP
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