CCNP - EIGRP

Notes Before Starting

 * EIGRP is Cisco proprietary.
 * EIGRP is an advanced distance-vector routing protocol.
 * EIGRP ASN's must match to become neighbors.

Starting EIGRP
1. Router(config)#router eigrp [asn] 2. Router(config-router)#network [ip] ([wildcard mask])
 * 1) Begins the EIGRP process.
 * 2) Enables EIGRP on an interface.

Advertising Routes
Router(config-router)#network [ip] ([wildcard mask])
 * Advertises a route to the given network.
 * Adds this network to it's topology table (see also - CCNP: EIGRP Tables)
 * Leaving the wildcard mask blank assumes a classful network.

EIGRP Table Maintenance

 * 1) EIGRP sends a neighbor discovery Hello packet.
 * 2) After finding a neighbor, does a Reliable Update (full routing update).
 * 3) EIGRP sends continuous Hello packets.
 * 4) Sends partial updates if a route changes or if a new route appears.

Hello and Hold Time Notes

 * By default, Hello packets are sent every 5 seconds.
 * By default, Hold Timers are set to 15 seconds.
 * When EIGRP receives a Hello packet, it resets its Hold Timer.
 * If the Hold Timer is reduced to 0, EIGRP considers the neighbor to have failed.
 * It's convention to have the Hello Interval and Hold Timers match other routers (but this isn't necessary).

Hello and Hold Timer Tweaking
1. Router(config-if)#ip hello-interval eigrp [asn] [x] 2. Router(config-if)#ip hold-time eigrp [asn] [x]
 * 1) Sets the Hello interval (time between Hello packets).
 * 2) Sets the Hold Timer.

Authentication
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Notes On Stub Routers

 * Used to drop the query scope to prevent EIGRP from becoming Stuck-In-Active.

Configuration
Router(config-router)#eigrp stub (parameters)
 * Parameters:
 * N/A - Defaults to 'connected' and 'summary'.
 * connected - Advertises connected routes matched with a 'network' command.
 * receive-only - Does not advertise routes.
 * redistributed - Advertises redistributed routes.
 * static - Advertises static routes if 'redistribute static' is configured.
 * summary - Advertises summarized routes.

Basics

 * Interfaces configured with the 'passive-interface' command do not multicast EIGRP Hello packets.
 * Used to prevent EIGRP from sending Hello packets on an interface that has no other EIGRP routers.

Configuration
Option 1 1. Router(config-router)#passive-interface [interface] Option 2 1. Router(config-router)#no network [ip of passive interface] 2. Router(config-router)#redistribute connected
 * 1) Option 1 (preferred)
 * 2) Makes the interface passive.
 * 3) Option 2
 * 4) Disables EIGRP on the interface.
 * 5) Redistributes the network.

Basics

 * Used to keep routing tables small.
 * Network should be designed with route summarization in mind.
 * Supported at any location in the network.
 * Reduces the Query scope.

Configuration
Router(config-if)#ip summary-address eigrp [asn] [prefix] [subnet mask]
 * Restarts the neighbor relationship.
 * After neighborship recovers, summary route is advertised.
 * Router does not advertise more specific routes contained in summary.
 * Summary route added to routing table with an outgoing interface of null0.
 * Locally, has a default administrative distance of 5.