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RE: How does OSPF enter routes into the routing table? posted 04/24/2002
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In this case, both should go into the table.

At 12:19 PM 4/24/2002 -0400, Sam.MicroGate@xxxxxxxxxxxxxx wrote:
I think you are correct. The same prefixes with two different subnet masks.
R4 receives 172.10.7.0/24 O IA and 172.10.7.0/28 O and then installs the /28
in the routing table. That is because, of cource, it is O.

Sam

-----Original Message-----
From: Ambern, Jeff [mailto:jambern@xxxxxxxxxxxxxxxxx]
Sent: Wednesday, April 24, 2002 11:25 AM
To: 'Sam.MicroGate@xxxxxxxxxxxxxx'
Cc: 'ccielab@xxxxxxxxxxxxxx'
Subject: RE: How does OSPF enter routes into the routing table?


I still believe that it has to do with the prefix being the same length and the first route is an intra-area route. Try making the /28 something other than subnet-zero and see the /24 shows up in the routing table.

Jeff

-----Original Message-----
From: Sam.MicroGate@xxxxxxxxxxxxxx [mailto:Sam.MicroGate@xxxxxxxxxxxxxx]
Sent: Wednesday, April 24, 2002 10:18 AM
To: jambern@xxxxxxxxxxxxxxxxx
Subject: RE: How does OSPF enter routes into the routing table?


What about the scenario below? did you take a look at it?


Sam

-----Original Message-----
From: Ambern, Jeff [mailto:jambern@xxxxxxxxxxxxxxxxx]
Sent: Wednesday, April 24, 2002 11:14 AM
To: 'Sam.MicroGate@xxxxxxxxxxxxxx'
Subject: How does OSPF enter routes into the routing table?


Ospf will insert Intra-Area routes into the routing table befor Inter-Area routes. The order of preference is: O IA E1 E2 Jeff


-------------------------------------------------------------------------- Hello all,

Last night I worked in a distribution lab from fatkid.com. In this lab I had
the following problem:
Area 2 is configured a virtual area between routers R5 and R4. I used area 0
range command to summarize the /28 subnet into area 2. Now the problem is R4
receive both routes the 172.10.7.0/28 as O and 172.10.7.0/24 as O IA and
strangely choose the first to install in the routing table. The /24 subnet
gets suppressed and does not make it to the routing table. Shouldn't I see
both routes in R4 because OSPF supports VLSM? Why OSPF choose the route with
the longer mask and ignored the one with shorter mask? If this the default
behavior, How can I make the summary address /24 reach R4. Thank you all for
your help.



172.10.7.0/28 172.10.128.0/26 LB0:172.10.5.4/24
R2------------------------------R5------------------------------R4----------
-------------------
area 0 area 2 area 3
Frame Relay Ethernet LB of R4

At R5:
area 0 range 172.10.7.0 255.255.255.0




Elsayed Mohamed Sr. Network Consultant Microgateds, Inc. 732-936-4413 _________________________________________________________________ Commercial lab list: http://www.groupstudy.com/list/commercial.html Please discuss commercial lab solutions on this list. _________________________________________________________________ Commercial lab list: http://www.groupstudy.com/list/commercial.html Please discuss commercial lab solutions on this list.
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