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Cloud and Networked Systems
Cloud and Networked Systems Topics
Computer Networks
Routing and Switching
350-401 ENCOR: Implementing Cisco Enterprise Network Core Technologies
WIP - 1.1.2 Lab - Implement Inter-VLAN Routing
2.1.2 Lab - Observe STP Topology Changes and Implement RSTP
Tune & Optimize EtherChannel Operations
NTP Security
OSPF
Exam Topics
300-410 ENARSI: Implementing Cisco Enterprise Advanced Routing and Services
300-415 ENSDWI: Implementing Cisco SD-WAN Solutions
Ethernet Local Area Networks
MAC Addresses
OSI and TCP/IP, IPv6 and Network Protocols at each layer
Intro to DHCP
802.1Q vs 802.1P (VLAN 0 Priority Tagging)
Domain Name System
What are webpages made of?
Top 1000 Well Known Ports
Zone-Based Policy Firewall (also known as Zone-Policy Firewall, or ZFW)
Wireless
Virtualization
Cloud Systems
macOS
Windows
Linux
Network Storage
Code
InfoSec
Infosec Topics
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OSPF
Open Shortest Path First or OSPF, is a link state routing protocol in which every router receives a complete picture of the network. This allows the routers in the OSPF domain to make routing decisions, using the full picture to map the shortest distance to its end destination.
All routers will select their own router ID (RID), providing the router with a unique identifier on the network. The topology of a network is stored in the Link State Database (LSDB), where the router IDs are used to identify each router using OSPF. \
​
Before you configure OSPF, you need to configure an ip address on the router's loopback interface. The loopback interface IP address determines the Router ID for the router. This can be used to influence which router ends up becoming the DR or BDR.
Purpose
Command
start ospf with router ospf <process id>
router ospf 1
specify the network and an area to assign those IPs to
network 10.10.10.1 0.0.0.255 area 0
Purpose
*each command can be made more specific
displays general information about OSPF routing
show ip ospf []
displays OSPF database on router
show ip ospf database []
displays information about OSPF enabled interfaces
show ip ospf interface []
displays neighbor information
show ip ospf neighbor []

LSAs **(Types & neighbor states) **

A LSA is a fundamental tool for OSPF to exchange routing information/topology with routers in the same area. LSAs are stored in the LSDB.** **
  • LSA Type 2: Network LSA
  • LSA Type 3: Inter-area prefix LSA
  • LSA Type 4: Inter-area router LSA
  • LSA Type 5: AS external LSA
  • LSA Type 6: Group Membership LSA
  • **LSA Type 7: Not-so-stubby area LSA **
  • **LSA Type 8: Link LSA **
  • LSA Type 9: Intra-area prefix LSA
Routers will reach FULL state when neighbors have exchanged their LSA databases
  1. 1.
    Down state
  2. 2.
    Attempt state
  3. 3.
    Init state
  4. 4.
    2-way state
  5. 5.
    Exstart state
  6. 6.
    Exchange state
  7. 7.
    Loading state
  8. 8.
    Full state

DR & BDR

OSPF uses DRs (designated routers) & BDRs (backup designated routers) to act as a hub for routers on the same broadcast segment to exchange OSPF information. The DR and BDR are the only routers in the segment who provide and receive OSPF information from every router. All Non-DR/BDR routers rely on the DR/BDR for updates. This helps to limit the number of routing updates needed throughout the segment.
An election process is used to decide which router will become DR and BDR. There are two factors in this decision:
  1. 1.
    **Priority - **The router with the highest priority will become the DR.
  2. 2.
    Router ID - If two routers have the same priority, the one with the higher Router ID will become the DR.
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Last modified 8mo ago
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Outline
Configure OSPF
LSAs **(Types & neighbor states) **
DR & BDR