Santhosh
Santosh P K wrote:
1. Router X receives an LSA that is inconsistent with its pre-
restart router-LSA. For example, X receives a router-LSA
originated by router Y that does not contain a link to X, even
though X's pre-start router-LSA did contain a link to Y. This
indicates that either a) Y does not support graceful restart,
b) Y never received the grace-LSA or c) Y has terminated its
helper mode for some reason (Section 3.2).
Why is it really required to validate the router LSA?
In all the above three cases mentioned the restarting router can come
to know about inconsistency in hello packet itself, as the hello
received by that restarting router from its previously adjacent
neighbor would contain a one-way.
a) Y does not support graceful restart,
b) Y never received the grace-LSA
Router X [running in graceful-restart mode] may send Hello prior
to receiving Hello from Router Y. In this case, inconsistency can be
detected from Y's router LSA.
c) Y has terminated its helper mode for some reason
Router Y, on terminating helper mode, need not send Hello with
one-way. Instead, it can reset the adjacency with Router X.
Regards
Sundar
-----Original Message-----
From: Santosh P K [mailto:[EMAIL PROTECTED]
Sent: Thursday, June 07, 2007 4:36 PM
To: [email protected]
Subject: [OSPF] graceful restart doubt
Hi all,
I have couple of doubt in graceful restart for ospf.
1. Router X receives an LSA that is inconsistent with its pre-
restart router-LSA. For example, X receives a router-LSA
originated by router Y that does not contain a link to X, even
though X's pre-start router-LSA did contain a link to Y. This
indicates that either a) Y does not support graceful restart,
b) Y never received the grace-LSA or c) Y has terminated its
helper mode for some reason (Section 3.2).
Why is it really required to validate the router LSA?
In all the above three cases mentioned the restarting router can come
to know about inconsistency in hello packet itself, as the hello
received by that restarting router from its previously adjacent
neighbor would contain a one-way.
2 Seciont 2 point 2
The restarting router runs its OSPF routing calculations, as
specified in Section 16 of [1]. This is necessary to return
any OSPF virtual links to operation. However, the restarting
router does *not* install OSPF routes into the system's
forwarding table(s) and relies on the forwarding entries that
it installed prior to the restart.
At wht point of time I need to run SPF when the router comes up?
Because after adjacency is formaed the restarting router exits
graceful restart and anyways at this point it calculates SPF and
update forwarding table.
Thanks and regards
Santosh P K
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