Cisco Networking Academy Program Semester 5 : Routing

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Cisco Networking Academy Program Semester 5
Routing

• Chapter 4
• OSPF In A Single Area

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OSPF

• OSPF Operation
• Configuring OSPF
• Verifying OSPF Operation

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Issues Addressed By OSPF

• Speed of convergence (event triggered updates)
• Support for Variable-Length Subnet Masking (VLSM)
  
• Network size (no limit)
• Use of bandwidth (incremental updates, multicast)
• Path Selection (better metrics)
• Grouping of members (hierarchy)

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OSPF Terminology
Flash
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OSPF Packet Types
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OSPF States

• Down no info exchanged
• Init Received a type 1 packet on an interface
• Two-Way Each OSPF routers know about each others
  (no data exchanged)
• Ex-Start Negotiation of relationship and
  sending of DBD
• Exchange Comparison of database and request for
  info.
• Loading Exchange of specific info.
• Full Link-State Databases converged.

Media
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OSPF Hello Protocol
Multicast address 224.0.0.5
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OSPF operations 5 steps
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Basic OSPF Configuration
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DR BDR configuration

• The router with the Highest IP address becomes
  the DR, the next one the BDR
• It can be modified by
• adding loopback interfaces
• (config)interface lo0
• (config-if)ip address 192.168.10.12
  255.255.255.0
• Setting the routers priority (before the election
  of the DR and BDR
• (config-if)ip ospf priority number

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Controling DR and BDR
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OSPF Costs

• To override the default cost (multi-vendor
  network)router(config)interface
  s0router(config-if)ip ospf cost 1000
• Dont forget to set the serial interface
  speedrouter(config-if)bandwidth 56

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OSPF authentication
router(config-if)ip ospf authentication-key
password router(config-if)ip ospf
message-digest-key key-id md5 encryption-type
password router(config-router)area number
authentication message-digest
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Configuring OSPF Timers
router(config)interface e0router(config-if)ip
ospf hello-interval 5router(config-if)ip ospf
dead-interval 20
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DR BDR Issues Types of OSPF Networks
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DR BDR Issues OSPF and Frame-Relay
Full-Mesh
Hub-and-Spoke Point-to-multipoint
Point-to-point
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DR BDR Issues Full Mesh topology (NBMA)
RTA(config)router ospf 1RTA(config-router)netwo
rk 3.1.1.0 0.0.0.255 area 0RTA(config-router)nei
ghbor 3.1.1.2RTA(config-router)neighbor 3.1.1.3
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DR BDR Issues Point-to-point
Point-to-point connection No DR/BDR election
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DR BDR Issues Hub-and-Spoke topology

• Only RTB can see the two other routers
• Priority must be set to 0 on RTA and RTC

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Adjacency and hub-and-spoke topology
router(config-if)ip ospf network
point-to-multipoint router(config-if)frame-relay
map ip address dlci broadcast
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Show Commands
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Debug Commands
routerdebug ip ospf ? adj OSPF adjacency
events events OSPF events flood OSPF
flooding lsa-generation OSPF lsa
generation packet OSPF packets retransmission
OSPF retransmission events spf OSPF spf tree OSPF
database tree
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