Hello all,

I'm trying to figure out the role of a designated router in a stub
network.

Consider a broadcast segment N with a single router X attached.

Firstly, can a stub network have a designated router? (a previous post
of John Moy's hints that a stub need not have a DR:
http://discuss.microsoft.com/SCRIPTS/WA-MSD.EXE?A2=ind0201&L=ospf&T=0&F=&S=&P=11786)

Here's why I think a stub network _can_ have a DR:

- The last paragraph of section 9.4 of rfc2328 implies that X will
become the DR for N:

        "Note also that if Router X is the only attached router that is
        eligible to become Designated Router, it will select itself as
        Designated Router and there will be no Backup Designated Router
        for the network."

So, as long as X's priority is not set to 0, it will elect itself the DR
of network N. I have not been able to find anything in 2328 that
mandates setting the priority of a router connected to a stub network to
zero. The only description of a stub I've been able to find is that it
has only one router (e.g. 2nd paragraph of page 15). Note that John's
January post shows that a broadcast segment with multiple routers can
still be considered a "stub" area so long as none of the routers are
elected DR).

So, if a stub network has a DR, what does that DR do? Again referring to
rfc2328, section 7.3 states:

---
    7.3.  The Designated Router
        Every broadcast and NBMA network has a Designated Router.  The
        Designated Router performs two main functions for the routing
        protocol:
        o   The Designated Router originates a network-LSA on behalf of
            the network.
---
- So the designated router of a stub network must originate a
network-LSA for that stub network. But sect. 12.4.2 says:
        12.4.2.  Network-LSAs
            A network-LSA is generated for every transit broadcast or
            NBMA network.  (A transit network is a network having two or
            more attached routers).  The network-LSA describes all the
            routers that are attached to the network.
---
- The stub network N is not a transit network. Should sec. 7.3 specify
that "every transit broadcast and NBMA network has a Designated Router."
?
Any thoughts and opinions are appreciated.
cheers,
Arthur

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