Drew,
If your VLANs are all covered by "network X.Y.Z.W area V" command under
"router ospf T" then they all are represented as Type-1/Type-2 LSA in OSPF
LSDB.
And every time a VLAN goes down, LSA-1/2 are reflooded with Age=MaxAge
(default 3600 sec).
When this VLAn goes back up, LSA-1/2 are recreated and reflooded again.
Every time this happens, all OSPF routers in given area must recalculate
their SPF, then put OSPF routes in a routing table with new timestamp.
I'd suggest to use OSPF "network" statement for core VLANs only, edge VLANs
should be injected with "redistrubute connected/static" statement (this
creates Type-5 LSA for edge VLANs which does not affect SPF).
HTH
Rgds
Alex
--------------------------------------------------
From: "Drew Weaver" <[email protected]>
Date: 30 November 2009 14:39
To: "Cisco-nsp" <[email protected]>
Subject: [c-nsp] OSPF clarification
Hi,
If you have your entire network in a single area (area 0), is it normal
that when a VLAN on any switch in that area flaps that all of your routes
in OSPF 'reset'?
I don't mean a 'neighbor' VLAN, I mean just any old VLAN with an IP
address assigned to it.
Last update from x.x.x.x on Vlan4061, 00:08:42 ago
I mean the 'timers' seem to reset for every single route in OSPF anytime a
single VLAN anywhere goes down.
If this is intended, which I am still not sure of, what would be the
proper way to 'area' a datacenter?
It doesn't seem like there would be a way to do it so that just the route
attached to said VLAN that is flapping would be removed/re-inserted unless
you put each VLAN in a separate area.
thanks,
-Drew
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