From: David Luu (wicked01@xxxxxxxxxxxxx)
Date: Sun May 19 2002 - 03:51:09 GMT-3
summary-address summarizes going into ospf, not out
if you looked at his config, the 135.1.20.0/22 subnet originated in ospf,
so the summary-address would not be advertised to igrp
since R4 is an ASBR, you need to summarize to a /24 by creating a second
ospf process and redistributing it into and using the summary-address
command on the first process
At 11:13 PM 5/18/2002 -0700, Jonathan Hays wrote:
>Yes - I know what you are thinking - this:
>
>http://www.cisco.com/warp/public/104/3.html#12.0
>
>"External Route Summarization
>
>External route summarization is specific to external routes that are
>injected into OSPF via redistribution. Also, make sure that external
>ranges that are being summarized are contiguous. Summarization
>overlapping ranges from two different routers could cause packets to be
>sent to the wrong destination. Summarization is done via the following
>router ospf subcommand:
>
> summary-address ip-address mask
>
>This command is effective only on ASBRs doing redistribution into OSPF."
>---
>The above CCO verbiage WOULD seem to indicate that the command is
>effective only one way. However, don't forget, this is an ASBR which
>also has the duty to tell external networks about what routes are
>available in the OSPF cloud.
>
>The configuration you gave is only the part where IGRP is redistributed
>into OSPF:
>
>router ospf 100
> router-id 4.4.4.4
> log-adjacency-changes
> summary-address 135.1.20.0 255.255.255.0
> redistribute igrp 100 subnets
>
>I haven't seen the write-up in question, but you are correct that the
>above configuration by itself does nothing to redistribute routes into
>IGRP. To do that statements like the ones below are needed:
>
>router igrp
> redistribute ospf 100 metric 10000 2000 255 1 1500 subnets
>
>And the trick here, is that since the 135.1.20.0/22 network has been
>summarized in OSPF as a /24, then *that* /24 is what gets redistributed
>into IGRP. This "trick" is necessary because IGRP won't understand the
>classless subnets. Essentially, you are using the OSPF ASBR's summary
>network statement to "adjust" the mask of OSPF classless networks to
>something that IGRP will understand.
>
>HTH,
>
>Jonathan
>
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Todd Spencer
>Sent: Saturday, May 18, 2002 4:54 PM
>To: ccielab@groupstudy.com
>Subject: FATKID 502 Expert Redistribution
>
>
>I am trying to do the FatKid 502 Expert Redistribution
>Lab, and I don't understand the solution provided. I
>will try to briefly explain.
>
>The problem has to do with the classic VLSM to FLSM
>problem (IGRP/OSPF). The lab requires that OSPF area
>4 be configured with a /22 subnet, and the IGRP domain
>be configured with a /24. OSPF area 4 is using the
>following subnet 135.1.20.x/22 and the IGRP domain is
>using 135.1.1.x/24. The OSPF configuration below is
>taken from the solution:
>
>router ospf 1
> summary-address 135.1.20.0 255.255.255.0
> redistribute igrp 1 subnets
> network 135.1.14.0 0.0.0.255 area 4
> network 135.1.20.0 0.0.3.255 area 4
>
>I am unsure what the summary-address command is doing
>in this configuration. How is it able to summarize a
>/22 into a /24? How is the /22 subnet getting into
>the IGRP domain? If anyone has done this lab and can
>provide assistance, it would be greatly appreciated.
>
>-Todd
>
>
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