Subject: About DR election after ospf graceful restart

From: Sanjay BM <[email-masked]>
Date: Tue, 29 Jun 2004 14:14:33 -0700

Hi,

I had couple of questions regarding DR election on helpers after a
OSPF graceful restart.

RFC3623 states the following:
---
When Router Y exits helper mode for X on a given network segment, it
   reoriginates its LSAs based on the current state of its adjacency to
   Router X over the segment.  In detail, Y takes the following actions:

      a) Y recalculates the Designated Router for the segment,

      b) Y reoriginates its router-LSA for the segment's OSPF area,

      c) if Y is Designated Router for the segment, it reoriginates the
         network-LSA for the segment and

      d) if the segment was a virtual link, Y reoriginates its router-
         LSA for the virtual link's transit area.
---

Question 1:
Should Router Y (helpers) recalculate the DR for the segment even when
it exits helper mode successfully i.e, when grace LSAs were flushed
before grace period expiry.

Question 2:
Assume Router X is of higher priority than Router Y and that Router X
was the BDR before going through a graceful restart. Should Router X
become the new DR for the segment when Router Y runs the DR election
after exiting helper mode?

Thanx,
Sanjay

---

From: Acee Lindem <[email-masked]>
Date: Tue, 29 Jun 2004 17:48:00 -0400

Hi Sanjay,

----- Original Message -----
From: "Sanjay BM" <[email-masked]>
To: <[email-masked]>
Sent: Tuesday, June 29, 2004 5:14 PM
Subject: About DR election after ospf graceful restart

> before grace period expiry.

There may be an optimization where in some cases it is unnecessary.
However, the algorithm is such that the existing DR should remain DR.  Also,
unless you have "lots" of neighbors on the subnet, it isn't all that expensive
to run.

> after exiting helper mode?

No. Unless other events come into play, whoever was DR prior to X's
restart should remain DR.

---

From: Sanjay BM <[email-masked]>
Date: Tue, 29 Jun 2004 16:06:06 -0700

Thanx Acee.