From: Michael Stout (michaelgstout@hotmail.com)
Date: Thu Sep 28 2006 - 20:05:43 ART
Yes, You should filter based on the metrics in your routing table and you
should not suppose that the path through the DR is more desirable.
If you see the path through the DR as more desirable you should move your
DR and see if the desirablilty of the routes follows the DR. I claim that
it will not.
The purpose of the DR is to provide the broadcast network with a
centralized source for network advertisments. All routers report their
links type 1 lsas to the DR and the DR calculates the type 2 network lsa
for each routere. This reduces network advertisement traffic.
You should consider link costs or distance commands if you want to
manipulate traffic flow.
Mike
--------------------------------------------------------------------
From: Alexei Monastyrnyi <alexeim@orcsoftware.com>
Reply-To: Alexei Monastyrnyi <alexeim@orcsoftware.com>
To: Tony Paterra <apaterra@gmail.com>
CC: Cisco certification <ccielab@groupstudy.com>
Subject: Re: OSPF DR advertisement question...
Date: Thu, 28 Sep 2006 23:49:06 +0200
Hi Tony.
In fact R5 will receive updates from both R3 and R4. R4 being DR for
Ethernet segment doesn't make any difference here, it is a kind of
"link local" entity.
Below all router are in area 0 and Ethernet segment R3<->R4 is
172.16.32.0/22, R1 (read R5 for your layout) is connected via PPP
links to both R3 and R4
Trafic share i tis case is 1, but this is irrelevant IMHO for route
propagation.
So you have to filter from both R3 and R4 on R5, I suppose.
====
R4#sh ip ospf nei
Neighbor ID Pri State Dead Time Address
Interface
3.3.3.3 1 FULL/BDR 00:00:33 172.16.34.3
Ethernet0/0
1.1.1.1 0
FULL/ - 00:01:54 172.16.124.2 Serial0/0
====
R3#sh ip ospf nei
Neighbor ID Pri State Dead Time Address
Interface
1.1.1.1 0 FULL/ - 00:00:37 172.16.13.1
Serial0
4.4.4.4 1 FULL/DR 00:00:30 172.16.34.4
Ethernet1
====
R1#sh ip ospf nei
Neighbor ID Pri State Dead Time Address
Interface
3.3.3.3 0 FULL/ - 00:00:34 172.16.13.3
Serial0
4.4.4.4 0
FULL/ - 00:01:50 172.16.124.4 Serial0.14
2.2.2.2 0
FULL/ - 00:01:38 172.16.124.5 Serial0.12
R1#sh ip route 172.16.32.0
Routing entry for 172.16.32.0/22
Known via "ospf 124", distance 110, metric 74, type intra area
Redistributing via eigrp 1
Advertised by eigrp 1 metric 10000 10 1 255 1500
Last update from 172.16.124.4 on Serial0.14, 00:08:41 ago
Routing Descriptor Blocks:
* 172.16.124.4, from 4.4.4.4, 00:08:41 ago, via Serial0.14
Route metric is 74, traffic share count is 1
172.16.13.3, from 4.4.4.4, 00:08:41 ago, via Serial0
Route metric is 74, traffic share count is 1
Tony Paterra wrote:
>Hey all, something I just noticed with broadcast networks in OSPF,
>curious if someone can confirm my rationale here...
>
>If I have 2 routers R3 and R4 in the same area (we'll call it area
>2)
>connected to an ethernet segment and R4 is the DR... Now if we have
>R5 in the same area (but not on the ethernet segment), R5 will
>receive
>the route to the ethernet segment from the DR (R4) only. I'm
>looking
>at this for purposes of filtering...
>
>
>R3 <-Eth--> R4 (DR)
> \ /
> \ /
> R5
>
>So if I didn't want to use bandwidth or cost to influence the
>traffic,
>what Router ID would I filter when I configure it on R5? R4's
>loopback or R3's?
>
>
>Also, under the "show ip ospf database" command, what does Link ID
>stand for? From the docs it looks like a network number, but for
>the
>router LSA's it looks like a description of a router.
>
>Thanks!
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This archive was generated by hypermail 2.1.4 : Sun Oct 01 2006 - 16:55:41 ART