Sixth Edition, Page 461

[Amr]

Hi,

I have noticed this little possible typo a year ago, and I didn't see anyone reporting it—or maybe I didn't get the concept 100% right.

On page 461, the output of the show ip ospf neighbor command for R3 and 871W says that the DR is R3, and BDR is 871W, while the 871W interface has a higher physical IP address, and there are no loopback interfaces set on both routers. This means that the 871W router should be the DR.

Can anyone help?

Cheers!

Amr

[lammle]

Not necessarily.

If a router interface comes up on a Broadcast or non-broacast multi-access network, it will have an election. It no other router responds to the election request, this interface will be the DR of that multi-access network.
If I configured the 871W after the R3 router, then the R3 would come up, win the election, and when the 871w came up with an election request, the R3 would tell the other router it was the DR for that multi-access network as the election has already taken place.

I have my students set up OSPF in class, and out of 20+ routers, it is never the one with the highest RID, so we raise the priorities and shutdown the DR and BDR to force another election and choose the DR for each network.

hope this helps.
Cheers!
Todd Lammle

[Amr]

Yes, that helped a lot! Thanks, Todd! :D