Thanks all for the different insights. Being in a teaching environment, these are just what i need to be able to explain the behavior/process in easier-to-digest terms.
Elmer ----- Original Message ----- From: "Priscilla Oppenheimer" To: Sent: Wednesday, January 30, 2002 5:33 PM Subject: Re: OSPF Startup questions [7:33711] > At 12:41 PM 1/30/02, Cebuano wrote: > >i would think that regardless if there's a new > >router with a higher RID that comes on line, the DR/BDR > >should be the default MASTER to initiate the exchange > >since he's got all the topology/links info in the area, except > >of course for scenarios where there is no DR/BDR. > > Both neighbors have information to send. The master/slave business is just > a temporary relationship to allow the neighbors to exchange their > information in a reliable fashion. There's no real reason for one router > instead of the other to become the master. Remember that protocol design is > modular. You should keep the database synchronization process separate from > the DR/BDR election. > > The synchronization process is the first step in the adjacency-building > process. Each router describes its database by sending a sequence of > database description packets to its neighbor. > > Each database description packet has a sequence number. Database > description packets sent by the master (polls) are acknowledged by the > slave through echoing of the sequence number. Both polls and their > responses contain summaries of link-state data. The master is the only one > allowed to retransmit database description packets. > > The OSPF protocol developers could have chosen some other method to ensure > reliability, such as opening a TCP session or inventing a client/server > protocol with the DR acting as the server on networks that have a DR. > Instead they invented a master/slave protocol. It's just how they decided > to implement it. If you think about it, you can see that their method has > some advantages. If you were in a computer science protocol development > class, you could write an essay on why their method is best. As a CCIE > candidate, however, I'm tempted to say, "why ask why?" ;-) > > Priscilla > > > >Elmer > >----- Original Message ----- > >From: "Rogell, Dennis" > >To: "'Cebuano'" > >Sent: Wednesday, January 30, 2002 12:19 PM > >Subject: RE: OSPF Startup questions [7:33711] > > > > > > > You can make the Dr the higher rid , and the answer to 3 is it looks at > > > sequence numbers not timestamps.If the information it receives is the > same > > > but the sequence number is greater that will be entered into ls database. > > > > > > hth > > > > > > Dennis Rogell CNE, CCNP > > > nextiraone > > > Formally Milgo Solutions > > > Email : [EMAIL PROTECTED] > > > Phone: (954) 846-5128 > > > > > > > -----Original Message----- > > > > From: Cebuano [SMTP:[EMAIL PROTECTED]] > > > > Sent: Wednesday, January 30, 2002 08:38 > > > > To: [EMAIL PROTECTED] > > > > Subject: OSPF Startup questions [7:33711] > > > > > > > > Hi, group. > > > > I have a few questions to iron out regarding OSPF startup. > > > > > > > > 1. EXSTART - master/slave is created between each router and its > >adjacent > > > > DR/BDR. > > > > Q: But this "election" on who the master will be is mute because > the > > > > router with the higher RID (thus) the DR/BDR acts as the master, right? > >If > > > > not, shouldn't the DR act as the master anyway since he ( or she) is > the > > > > central distribution point for the area's topology? > > > > > > > > 2. LOADING - slave router sends an LS request if the master's DBD has a > > > > more > > > > up-to-date link-state entry. > > > > Q: "up-to-date" meaning timestamps?? But...what if there's no NTP > > > > server > > > > to synchronize them? > > > > > > > > Thanks. > > > > Elmer > ________________________ > > Priscilla Oppenheimer > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=33820&t=33711 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
