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EIGRP - Coggle Diagram
EIGRP
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EIGRP Characteristics
EIGRP Basic Features
Diffusing Update Algorithm
(DUAL)
- EIGRP uses DUAL as its routing algorithm.
- DUAL guarantees loop-free and backup paths throughout the routing domain.
Establishing Neighbor
Adjacencies
- EIGRP establishes relationships with directly connected EIGRP routers.
- Adjacencies are used to track the status of these neighbors
Reliable Transport
Protocol
- EIGRP RTP provides delivery of EIGRP packets to neighbors.
- RTP and neighbor adjacencies are used by DUAL.
Partial and Bounded
updates
- Instead of periodic updates, EIGRP sends partial triggered updates when a path or metric changes.
- Only those routers that require the information are updated minimizing bandwidth use.
Equal and Unequal Cost
Load Balancing
- EIGRP supports equal cost load balancing and unequal cost load balancing, which allows
administrators to better distribute traffic flow in their networks
▪ EIGRP uses protocol-dependent modules (PDMs) to support different protocols such as IPv4, IPv6,
and legacy protocols IPX and AppleTalk.
PDMs are responsible for:
- Maintaining EIGRP neighbor and topology tables
- Computing the metric using DUAL
- Interfacing DUAL and routing table
- • Implementing filtering and access lists
- Performing redistribution with other routing protocols
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▪ EIGRP supports authentication
and is recommended.
- EIGRP authentication ensures that routers only accept routing information from other routers that has been configured with the same password or authentication information.
EIGRP Packet Types
- IP EIGRP relies on 5 types of packets to maintain its various tables and establish complex
relationships with neighbor routers.
EIGRP PACKET TYPES
- Hello
Discover other EIGRP routers in the network.
- Update
Convey routing information to known destination.
- Acknowledgement
Acknowledgement the receipt of any EIGRP packet.
- Query
Request specific information from a neighbor router.
- Reply
Respond to a query.
Hello packet are used to discover and form adjacencies with neighbors.
- On hearing Hellos, a router creates a neighbor table and the continued receipt of Hellos maintains the table.
- Hello packets are always sent unreliably.
- Therefore Hello packets do not require acknowledgment.
EIGRP Update packets are used to
propagate routing information.
- Sent to initially exchange topology
information or topology change.
- EIGRP updates only contains needed routing information and are unicast to routers that require it.
- Update packets are sent reliably and therefore requires acknowledgements.
- Acknowledgements packets are "dataless" Hello packets used to indicate receipt of any EIGRP packet during a "reliable" exchange.
- Used to acknowledge the receipt of Update packets, Query packets, and Reply packets.
- Query and reply packets are used by
DUAL when searching for networks.
- They both use reliable delivery and
therefore require acknowledgement.
- Queries can use multicast or unicast, whereas Replies are always sent as unicast.
EIGRP Messages
- ▪ EIGRP frame contains destination multicast
address 01-00-5E-00-00-0A.
- The IP packet header contains destination IP address 224.0.0.10 and identifies this packets as a EIGRP packets (protocols 88)
- The data portion of the EIGRP message includes:
Packet header - The EIGRP packets header identifies the type of EIGRP message.
- Type/Length/Value (TLV) - The TLV field contains EIGRP parameters, IP internal and external routers.
- EIGRP for IPv6 is encapsulation using an IPv6 header with multicast address FF02::A and the next header field set to protocols 88.
- EIGRP message include the header with an Opcode field that specifies the type of EIGRP packet (Hello, Ack, Query, and Reply) and the AS number field.
Verify EIGRP with IPv4
show ip protocols - Displays the parameters and current state of the active routing protocol processes. For EIGRP, this command shows the EIGRP autonomous system number, filtering and redistribution numbers, and neighbors and distance information.
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