From: Baety Wayne 18 CS/SCBX (Wayne.Baety@xxxxxxxxxxxxx)
Date: Thu Apr 25 2002 - 07:37:31 GMT-3
On R2 you must use the following command under the ospf process...
area 0 range 140.1.20.0 255.255.255.0
This will range the 140.1.20/27 network into a /24 to be advertised into
area 1. Part of the stipulation of using the range command requires
multiple areas. It will summarize the route with a new LSA (Type 3 Summary
LSA) to be distributed into all other areas than the area on which it is
configured. For this to be successful at least 1 LSA containing a longer
prefix network must exist in the topology database in the area on which it
is configured. So this command must be configured in the area in which the
longer prefix network LSA originates.
However, since R1 in your scenario is a member of Area 1 and is not a Area
Border Router (ABR), configuring the area range command will not generate a
type 3 LSA since R1 has no other adjoined areas to advertise this
information into. Therefore configuring 140.1.200/29 to be summarized with
the area 1 range command would have no effect on R1. If you configure the
range command on R2, R2 being an ABR, will advertise this information to R3,
which is in another area. R1 will not receive the advertisement, since R2
will not advertise the LSA into the area that it is configured (See my
previous post concerning internal split horizon which dramatizes the effect
of doing so). Therefore, R1 will not have the information to redistribute
into IGRP.
To be able to advertise the 140.1.200/29 into IGRP as a summarized
140.1.200/24 route, you must create a second ospf process on R1,
redistribute the first ospf into the second and apply the summary-address
140.1.200.0 255.255.255.0 command to the second ospf process. See below...
router ospf 1
....
router ospf 2
redistribute connected
summary-address 140.1.200.0 255.255.255.0
router igrp 1
redistribute ospf 1 metric 2000 200 1 255 1500
redistribute ospf 2 metric 2000 200 1 255 1500
once you redistribute ospf 1 into ospf 2 (or connected into ospf 2), the
ospf 2 process will be configured as an ASBR and will be allowed to
summarize routes redistributed into it with the summary-address command.
However, in this case since the 140.1.200/29 network is a directly reachable
network on R1 you must use the redistribute connected command, as shown
above. Alternatively, you could have configured the summary-address command
here instead of using an area range command on R2. And it is important that
you realize that doing so allows you to avoid affecting your OSPF domain
with your summarized prefix.
WAYNE BAETY, MCSE, A1C, USAF
Network Systems Trainer
> -----Original Message-----
> From: Alex Paulino [mailto:Alex@2s.com.br]
> Sent: Thursday, April 25, 2002 11:47 AM
> To: ccielab@groupstudy.com
> Subject: ospf and igrp
>
> Hi all, i know that this subject already was commented, but i'm still in
> doubt.
>
> R0)-----140.1.56.0/24 -----R1 -----140.1.200.0/29 -----------R2
> -------140.1.20.0/27-----------R3
>
> Between: R0 and R1 - IGRP
> between: R1 and R2 - OSPF AREA 1
> between:R2 and R3 - OSPF AREA 0
>
> 1) My problem is the /27 (area0) and /29 (area1) doesn't appear in R0
> (igrp).
> I have tried to put a "area 1 range 140.1.200.0 255.255.255.0" in R2 or
R1,
> and, this route never up in R0. I don't know if is correctly.
>
> 2) I don't know what to do in /29 case. :-(
>
> thanks for help
>
>
> Alex
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:58:19 GMT-3