From: ccie2b@xxxxxxx
Date: Tue Jan 16 2001 - 22:49:58 GMT-3
Thanks Julie Ann! You da woman!
Devinator
ccie2b@usa.net
> Hi,
> I emphasize with you because I am always hung up on this issue.
> How I have come to resolve it is this:
> 1. remember that IGRP can only accept routes with the same subnet mask as
> it's interface. So if the IGRP interface
> is a 24 bit subnet mask, then you will only get 24 bit routes redistributed
> from OSPF into IGRP (same applies to RIP V1). This rule does not apply if
> the route is in a different classfull network and then it will summarize to
> the classfull boundary.
> 2. to solve this problem you have 3 choices:
> a. if possible - summarize at OSPF Area border routers. Say if you
> have an area 3 with a /28 bit subnet mask, use area 3 range x.x.x.x
> 255.255.255.0 to summarize to the /24 bit mask and then it will get
> redistributed into IGRP.
> b. on the redistribution router create a static route to null 0 to
> summarize to the 24 bit boundary, ip route x.x.x.x 255.255.255.0 null 0 and
> redistribute static into IGRP.
> c. use a ip default-network on the redistribution router or a
> downstream IGRP router. Remember that the default network must
> point to another address range. so if your address range is
> x.x.x.x the default route must point to y.y.y.y. This installs
> a gateway of last resort into your routing table. Remember that
> IGRP does not use the 0.0.0.0 route.
> 3. Always look at your ospf database to make sure that you did not
> redistribute in connected routes that you specified as
> passive under IGRP. do a show ip ospf database and go to the very bottom
> and look at your external LSA's. Make sure that
> you only have the external LSA's that you expected. Use route-maps to
> filter connected subnets and other network as necessary and
> then recheck the IP OSPF database. Unfortunately IGRP does not have a
> database to check - so you always have to
> do a debug on igrp routing or check a downstream router. If you are doing
> EIGRP you can do
> a show ip eigrp topology to make sure that you have only redistributed into
> eigrp the routes that you expected.
> good luck - I go in 10 days. eeeeeeeeeeeeeeeeeeeeeeeeeeeee!!!!!!!!
> read up on VLSM. check out the tech tips on CCO. Set up 4 routers and
> redistribute between protocols. Make sure that
> you do it very deliberately. That is set up all the protocols to not
> redistribute, look at the databases and routing tables. Start one by
> one and redistribute, then watch what happens. Make sure you use a variety
> of masks and classfull and non-classfull networks.
> Never never put in multiple redistribution statements without checking the
> databases after adding each statement and making sure you do not need to
> filter.
> Julie Ann
> At 09:01 AM 1/16/2001 -0500, ccie2b@usa.net wrote:
>>Familiar with most issues, but this one keeps eluding me for some
>>reason...never had anyone explain it...and yes, 2 weeks and
>>closing...need help, not criticism...
>>
>>Devinator
>>
>>
>>
>> > You are walking into the lab in 2.5 weeks and you are unfamiliar with
>> > classful versus classless issues?
>>
>> > -----Original Message-----
>> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>> > ccie2b@usa.net
>> > Sent: Monday, January 15, 2001 7:37 PM
>> > To: ccielab@groupstudy.com
>> > Subject: aggregate addresses and redistribution
>>
>> > I keep hearing about having OSPF and igrp (or rip) having to have
>> > matching masks or something. I don't understand what this is, applies
>> > to, etc. Can someone enlighten me in layman's terms as to this
>> > mask-matching thing?
>>
>> > Thanks ALOT,
>>
>> > Devinator
>> > ccie2b@usa.net
>>
>>
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:27:32 GMT-3