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8-5
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
OL-20002-02
Chapter 8 Configuring EIGRP
Information About EIGRP
• Graceful Restart and High Availability, page 8-7
Address Families
EIGRP supports both IPv4 and IPv6 address families. For backward compatibility, you can configure
EIGRPv4 in route configuration mode or in IPV4 address family mode. You must configure EIGRP for
IPv6 in address family mode.
Address family configuration mode includes the following EIGRP features:
• Authentication
• AS number
• Default route
• Metrics
• Distance
• Graceful restart
• Logging
• Load balancing
• Redistribution
• Router ID
• Stub router
• Timers
You cannot configure the same feature in more than one configuration mode. For example, if you
configure the default metric in router configuration mode, you cannot configure the default metric in
address family mode.
Authentication
You can configure authentication on EIGRP messages to prevent unauthorized or invalid routing updates
in your network. EIGRP authentication supports MD5 authentication digest.
You can configure the EIGRP authentication per virtual routing and forwarding (VRF) instance or
interface using key-chain management for the authentication keys. Key-chain management allows you
to control changes to the authentication keys used by MD5 authentication digest. See the Cisco Nexus
7000 Series NX-OS Security Configuration Guide, Release 4.x, for more details about creating
key-chains.
For MD5 authentication, you configure a password that is shared at the local router and all remote
EIGRP neighbors. When an EIGRP message is created, Cisco NX-OS creates an MD5 one-way message
digest based on the message itself and the encrypted password and sends this digest along with the
EIGRP message. The receiving EIGRP neighbor validates the digest using the same encrypted password.
If the message has not changed, the calculation is identical and the EIGRP message is considered valid.
MD5 authentication also includes a sequence number with each EIGRP message that is used to ensure
that no message is replayed in the network.
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