EIGRP Basics (ROUTER ID)

EIGRP Router ID is an important component to EIGRP and is a way for EIGRP to identify each router that is participating in the EIGRP ASN domain.

The EIGRP enabled router uses the following 3 steps to determine its ID:

  1. Manual configuration within the EIGRP config
  2. Highest IPv4 address on an enabled and operating loopback interface
  3. Highest IPv4 address on an enabled and operating non loopback interface

Manually configuring an EIGRP Router ID:

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EIGRP Basics (Manipulating EIGRP Hello and Hold Timers)

EIGRP works perfectly fine with its stock settings. However, there comes a time when settings need to get tweaked for various reason. EIGRP by default sends Hello packets every 5 seconds and has a Hold timer of 15 seconds. This means, by default, a router will send a hello packet every 5 seconds, and wait 15 seconds to receive a hello packet from its neighbors before it drops that route.

Hello packet set by each neighbor every 5 seconds:

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CCNP Routing & Switching ROUTE 300-101 Chapters 1 & 2 Notes Part II

CCNP Routing & Switching ROUTE 300-101 Chapters 1 & 2 Notes:

  • TCP/IP Fundamentals
    • Routing occurs at Layer 3 of the OSI Model
    • Internet protocol (IP) is the primary protocols used to route traffic
      • Today we have the almost exhausted IPv4 and the new IPv6 addressing to chose from to route traffic.
      • At Layer 4 we have the Transport layer, which determines the way traffic is going to flow once it hits layer 3. TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are the two transport layer protocols.
      •  The IP header is where things like type of QoS, TCP/UPD, IPv4/IPv6 are determined.
      • Maximum Transmission Unitdetermines the size of the packet being transmitted.
      • ICMP messagesaids in checking networking connectivity
      • Three-Way Handshakesince TCP is a reliable protocol, the 3-way handshake is one of a few items which make this possible. The 3-way handshake allows the source and destination devices to establish a session by which packets are going to be sent.
      • TCP WindowingAllows each packet to get a sequence number which ensures that all packets are sent & recieved between the sender and receiver. 

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CCNP Routing & Switching ROUTE 300-101 Chapters 1 & 2 Notes Part I

CCNP Routing & Switching ROUTE 300-101 Chapters 1 & 2 Notes:

  • There is a natural need for routing protocols
    • The use of layer 3 devices
    • Scalability
      • The most common routing protocols used in an enterprise/campus networks are versions or RIP, EIGPR, OSPF
      •  Most common routing protocol used for external/untrust (Internet) networks is BGP
    • There are 3 Routing Protocol Categories
      • Distance Vector (Sends full copy of the routing table at certain interval)
        • Distance-Vectore routing protocols use one of the following approaches to prevent routing loops:
          • Split Horizon – This is when an interface is prevented to advertise a route which it already learned on that interface. 
          • Poison ReverseThis is when an interface receives a route advertisement but then re-advertises the same route out with a metric considered infinite.

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