Monday, 12 September 2016

OSPF - Part 3

OSPF Router-id



1.)  It is 32-bit number assigned to each router running the ospf protocol.
2.)  It is uniquely identify of the router within an autonomous number.
3.)  It elects based on highest loopback ip address of router, otherwise highest non-loopback 
       ip  address of router.
4.)  We can set manually ospf router id:
       In ospf router subcommand:   router-id <router-id>


OSPF  Feature 

1.)  Transport
        IP protocol type 89 (Does not use TCP and UDP)
        OSPF need to perform reliable multicasting because it need talk to multiple possible neighbor 
        on the same network segment. Now, TCP does not support multicasting and UDP is reliable
        not.  Therefore, OSPF implements its own transport mechanism that allows both for reliability 
         (acknowledgments and retransmission of lost segments) and multicasting, bypassing both TCP 
         and UDP. 

2.)  Metric
        Based on cost of all outgoing interfaces in a route.

3.)  Hello interval
       Interval which route sends OSPF hello messages out of an interface. By default OSPF send hello
       messages in every 10 second on ethernet link and 30 second on WAN link.
   
       Note : OSPF send fast hello messages less than 1 second.
       Follow this link:
      

http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fasthelo.html#wp1027195

 4.) Dead - Timer
       Timer used to determine when neighbor router has failed. OSPF router send dead message every 
        40 second. 

 5.)  Update Destination address
        Normally send to 224.0.0.5 (all SPF router) and 224.0.0.6 (all DR) router.

 6.)  Full or Partial update
       Full update used when new neighbor are discovered. Partial update used otherwise.

7.)  Authentication
      Support MD-5 and Clear-text authentication.
  

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