1. Static
  2. Dynamic
    1. Distance Vector
      1. RIP
      2. IGRP
      3. EIGRP
        1. MM métrica (x256)
        2. Metrics (static values)
          1. Bandwidth (default)
          2. Delay (default)
          3. Reliability
          4. Load
        3. Packet
          1. Opcode
          2. UPDATE
          3. Propagate new information after changes
          4. QUERY
          5. Subtopic 1
          6. REPLY
          7. Response to query
          8. HELLO
          9. Keep-alive (5s or 60s on non-broadcast multi-access nets)
          10. Autonomous System (AS) Number (1..65536)
          11. Same for adjacent routers involved
          12. Flags
          13. Sequence
          14. ACK
          15. Numbers (TLV format)
          16. Values
          17. Hold Time
          18. Max time to wait for HELLO (default 3x HELLO time)
          19. K-Values (same for adjacent routers)
          20. K1 (bandwidth)
          21. saves mininmum bandwidth
          22. K2
          23. K3 (delay)
          24. accumulation of delays
          25. K4
          26. K5 (reliability)
          27. 0-255
          28. AD
          29. EIGRP Summary Route (5)
          30. EIGRP Internal (D) (90)
          31. EIGRP external (DEX) (170)
        4. Pro
          1. Can convey internal and external information in Numbers
          2. User Protocols Dependent Modules (PDM) for different network protocols
          3. Complete topology overview inside AS
        5. Cons
          1. Requires more resources than RIP
        6. Uses Diffusion Update Algorithm (DUAL)
          1. Prevent routing loops
          2. Find loop-free primary routes
          3. Keep a list of free backup loop-routes (have different metrics thatn primary)
          4. Concepts
          5. Successor (S)
          6. Lleast-cost route to the destination network
          7. N successors means load-balancing
          8. Feasible Distance (FD)
          9. Lowest calculated metric to reach the destination network
          10. Feasible Successor (FS)
          11. Loop-free backup route
          12. Routes for which RD_A is < FD_A
          13. Reported Distance (RD)
          14. Lowest calculated metric to reach the destination network
          15. Told to a router by neighbors
          16. Feasibility Condition (FC)
          17. RD to a network is less that FD to a given network
          18. Advertise Distance (AD)
          19. Subtopic 1
        7. Transported over Real Time Protocol (RTP)
          1. Reliable
          2. UPDATE
          3. QUERY
          4. REPLY
          5. Unreliable
          6. HELLO
          7. ACK
        8. Sent in
          1. Unicast (bounded update)
          2. REPLY
          3. QUERY
          4. Multicast (224.0.0.10)
          5. QUERY
        9. On cold start sends routing tables
        10. Route summarization by default (same issue as RIP)
        11. Use same AS number for router in same routing domain
        12. Point auto-summarization to Null interface to avoid unecessary updates
        13. Change interface bandwidth to a specific value
        14. Allows manual summarization by interface
        15. Timers can be different
          1. If changed keep recommended ratio
        16. Supports authentication
        17. Process-id is the same as ASN
    2. Link-State (LS)
      1. Open Shortest Path First (OSPF)
        1. Packet Header
          1. Router ID
          2. Area ID
          3. Type
          4. HELLO
          5. Discover neighbors and build adjacencies
          6. Usually multicast (224.0.0.5)
          7. DATABASE DESCRIPTION (DBD)
          8. Checks for database synchronization between router
          9. LINK-STATE REQUEST (LSR)
          10. Eequest specific LS records
          11. LINK-STATE UPDATE (LSU)
          12. Contains up to 10 LS Advertisements (LSA)
          13. Unencrypted updates
          14. LINK-STATE ACK (LSAck)
          15. ACK of previous packets
          16. Designated Router (DR)
          17. Conveys updates to other OSPF routers
          18. Backup DR (BDR)
          19. Takes over DR if it fails
          20. Hello Interval (usually 30s)
          21. Router Dead Interval (usually 4x Hello Interval)
          22. List of Neighbors
          23. Authentication
        2. Algorithm
          1. 1) LS Database
          2. 2) Apply SPF algorithm
          3. 3) SPF Tree
          4. 4) Derive "best" routing table
        3. AD (110)
        4. Supports authentication
        5. Process-id is not the same as Area ID and can be different among routers in a given area
        6. Router ID
          1. IP address that identifies a router
          2. Criteria to decide
          3. 1) Manually defined (# router-id)
          4. 2) Highest IP address of loopback interfaces
          5. 3) Highest IP address of active interfaces
        7. Adjacency conditions
          1. Same subnet masks
          2. Routers must be in the same area (Area ID)
          3. Must use the same authentication scheme (Authentication)
          4. Hello and Router Dead Intervals must be equal among routers to establish adjacencies
          5. Same Network Types
        8. Troubleshooting
          1. Missing or incorrect network defined
        9. Use Loopback Address for OSPF stability because it cannot fail
        10. Router States
          1. 1) Down
          2. 2) Init
          3. 3) 2-way
          4. Hello to find neighbors
          5. 4) Exchange Start
          6. How starts sending packets
          7. 5) Exchange
          8. Exchange LSR e LSU
          9. 6) Loading
          10. 7) Full
          11. All information is exchanged
        11. In multi-acess networks
          1. State = FULL, if router is DR or BDR
          2. State = 2Way, if router is DROTHERS
        12. No automatic summarization
        13. Cost based on bandwidth
          1. Based on interface bandwidth (by default 100 Mbps)
          2. Can be modified (auto-cost reference-bandwidth)
        14. 5 network types
          1. Point-to-Point (e.g. serial interfaces)
          2. No DR/BDR election
          3. Broadcast Multi-Access (BMA)
          4. Non-Broadcast Multi-Access (NBMA)
          5. Point-to-MultiPoint (Serial interfaces)
          6. Virtual Links
          7. used to transmit routing information between different areas other than 0
        15. 2 Challenges in Multi-Access Networks
          1. Multiple Adjacencies
          2. Excessive flooding LSA
          3. Excessive bandwidth use + chaotic traffic
          4. Solution
          5. Use DR and BDR
          6. LSA sent to 224.0.0.6 where DR/BDR are listening
          7. DR forwards LSA to 224.0.0.5
          8. Routers are elected to send/receive LSA
          9. Default interface priority is 1
          10. Election criteria precedence
          11. 1) DR (1st highest OSPF interface priority)
          12. 2) BDR (2nd highest OSPF interface priority)
          13. 3) Highest router-id
          14. Timing of election
          15. As soon as the 1st OSPF router enabled interface is active
          16. DR fails
          17. OSPF process in DR fails
          18. Multiacess interface on DR fails
          19. Manipulate election
          20. 1st start DR then start BDR
          21. Sequentially change interface states
          22. 1st interface up is DR the 2nd BDR
      2. Intermediate System-to-Intermediate System (IS-IS)
      3. Shortest Path First (SPF) using Uses Dijkstra (based on lowest cost)
      4. Uses LS Packet (LSP)
        1. State of each directly connected (adjacent) link
        2. Flood to neighbors except source of LSP
        3. Sent
          1. On router initial startup
          2. After LS changes
      5. Builds topological map
      6. Router independently determines shortest path to all networks
      7. Fast Convergence
      8. Event-driven updates
        1. Periodic HELLO to find neighbors
      9. Cons
        1. Higher requirements (memory, processing and bandwidth)
      10. Link-State Routing Process
        1. 1) Router learns about its own links, its own directly connected networks
        2. 2) Each router is responsible for meeting its neighbors on directly connected networks
        3. 3) Each router builds a LSP containing the state of each directly connected link
        4. 4) Each router floods the LSP to all neighbors, who then store all LSPs received in a database
        5. 5) Each router uses the database to construct a complete map of the topology and computes the best path to each destination network
      11. Prevents routing loops by building a complete and synchronized view of the network
    3. Path Vector
      1. BGP
    4. Classification
      1. Network classes
        1. Classful
        2. Classless
      2. Update strategy
        1. Unicast
        2. Broadcast
        3. Multicast
      3. Information completeness
        1. Partial
        2. Full
      4. Update targets
        1. Bounded
        2. Unbounded
      5. Timing of updates
        1. Triggered
        2. Periodic
    5. Use #passive-interface command to prevent sending packets out a specific interface
  3. Table
    1. Levels
      1. Ultimate Route
        1. Routes with next-hop IP address and/or exit interface
      2. Level 1 Ultimate Route
        1. Supernet route
        2. Network route
        3. Default route
        4. Deleted when the last level 2 route is removed
      3. Level 1 Parent route
        1. Does not have an ultimate route
        2. Indicates presence of level 2 routes
        3. Created when subnets are added to the routing table
        4. Variably subnetted
          1. 2 or more child routes with different masks belong to the same classful network
        5. Subnetted
          1. All child routes share the same mask
      4. Level 2 routes (Child routes)
        1. Subnet of a classful network address
        2. Are Ultimate Routes
    2. Always uses a classful scheme
  4. Classful & Classless
    1. Routing Protocols
      1. how to populate routing table
    2. Routing Behaviors
      1. How to search routing table