• Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
    Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.

OSPF EXSTART state terminology question

BobSutan

BobSutan

[H]F Junkie
Joined
Apr 5, 2000
Messages
12,226
I'm brushing up on OSPF and came across something I could use some explaining with.

In regards to routers that have bidirectional communication (both in the 2WAY state), when referring to routers that are in the exchange process and about to begin the EXSTART state, would it be true to term said routers as Master/Slave, or are we simply talking about DR/BDRs and the author decided to just use different terminology? (This is largely like DR/BDR behavior since the router with the highest Router ID will begin the sending of the DBDs.)

In short, I'm confused as to why the authors choose the Master/Slave terminology for the EXSTART state.

Note: the book I'm referencing is CCNP:2.0 Routing by Robert N. Myhre
 
cisco press' "ospf network design solutions" and "ccie professional development: routing tcp/ip volume 1" both use the master/slave terminology...

it's true the selection process is the same, but to different ends.

regards,
steve
 
Master/Slave is used when forming neighbor adjacencies. Each neighbor will send Data Descriptor Packets with the master going first.

The router with the highest IP address will become the master.

I would assume the Exstart phase is unicast.

After a router has reached a full state then the DR is used to receive LSAs on multicast 224.0.0.6 from any router that receives a link state change. They then flood that LSA out to 224.0.0.5 (DROTHER).
 
You are correct. The EXSTART process of sending DBD packets is unicast.

I've also found another explanation of the EXSTART phase in my old ACRC book.

In the EXSTART state, the DR and BDR establish adjacencies with each router in the network. During this process, a master-slave relationship is created between each router and its DR/BDR. The router that has the higher router ID acts as the master.
Click to expand...

What it is lacking is why the master-slave relationship is significant, which as I've found out is that the Master initiates the DBD exchange by polling (and the DBD exchanges are "synched" by using the Master's sequence number).
 
You must log in or register to reply here.
Back
Top