Specifications

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Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, Release 5.0(3)U2(2)
OL-25782-02
Chapter 4 Configuring EIGRP
Information About EIGRP
When using EIGRP stub routing, you need to configure the distribution and remote routers to use EIGRP
and configure only the remote router as a stub. EIGRP stub routing does not automatically enable
summarization on the distribution router. In most cases, you need to configure summarization on the
distribution routers.
Without EIGRP stub routing, even after the routes that are sent from the distribution router to the remote
router have been filtered or summarized, a problem might occur. For example, if a route is lost
somewhere in the corporate network, EIGRP could send a query to the distribution router. The
distribution router could then send a query to the remote router even if routes are summarized. If a
problem communicating over the WAN link between the distribution router and the remote router occurs,
EIGRP could get stuck in active condition and cause instability elsewhere in the network. EIGRP stub
routing allows you to prevent queries to the remote router.
Route Summarization
You can configure a summary aggregate address for a specified interface. Route summarization
simplifies route tables by replacing a number of more-specific addresses with an address that represents
all the specific addresses. For example, you can replace 10.1.1.0/24, 10.1.2.0/24, and 10.1.3.0/24 with
one summary address, 10.1.0.0/16.
If more specific routes are in the routing table, EIGRP advertises the summary address from the interface
with a metric equal to the minimum metric of the more specific routes.
Note EIGRP does not support automatic route summarization.
Route Redistribution
You can use EIGRP to redistribute direct routes, static routes, routes learned by other EIGRP
autonomous systems, or routes from other protocols. You configure route map with the redistribution to
control which routes are passed into EIGRP. A route map allows you to filter routes based on attributes
such as the destination, origination protocol, route type, route tag, and so on. See Chapter 13,
“Configuring Route Policy Manager.”
You also configure the default metric that is used for all imported routes into EIGRP.
Load Balancing
You can use load balancing to allow a router to distribute traffic over all the router network ports that are
the same distance from the destination address. Load balancing increases the utilization of network
segments which increases effective network bandwidth.
Cisco NX-OS supports the Equal Cost Multiple Paths (ECMP) feature with up to 16 equal-cost paths in
the EIGRP route table and the unicast RIB. You can configure EIGRP to load balance traffic across some
or all of those paths.
Note EIGRP in Cisco NX-OS does not support unequal cost load balancing.
Split Horizon
You can use split horizon to ensure that EIGRP never advertises a route out of the interface where it was
learned.