From: Connary, Julie Ann (jconnary@xxxxxxxxx)
Date: Fri Dec 29 2000 - 11:02:32 GMT-3
Brian,
If I understand correctly - when you redistribute the routes set a tag on
them and then deny on
the return redistribution? i.e.
router ospf 1
redistribute eigrp 1 subnets route-map checktag
router eigrp 1
redistribute ospf 1 route-map checktag2
route-map checktag deny 10
match tag 3
route-map checktag permit 20
set tag 2
route-map checktag2 deny 10
match tag 2
route-map checktag2 permit 20
set tag 3
If I'm correct the route-map checktag will deny any route with a tag set to
3 - i.e. an already redistributed route and will set the
tag on any newly redistributed routes to 2. Here is a graphic, this will
deny route 10.1.0.0 from being redistributed back into OSPF because it's
tag is set to 2.
OSPF domain ------- Redistribution Router ---------------EIGRP domain
10.1.0.0 --------------> redistribute, set tag=2 10.1.0.0
with tag=2
11.1.0.0 with tag=3------X deny tag=3
11.1.0.0 with tag=3 redistribute, set tag=3, <------------
11.1.0.0
deny tag =
2 X---------10.1.1.0 with tag=2
Of course this assumes that no other routers are setting tags.
Julie Ann
At 05:26 PM 12/28/2000 -0500, Brian Hescock wrote:
>In addition to distribute lists and the typical way we do route-maps, you
>can also tag the routes so you don't have to worry about matching networks
>all the time. Just tag the networks once then you can do a permit or deny
>based upon the tag. Below is a url that covers it. Everyone should try
>it at least once because you know how it is, if it can be configured on a
>Cisco router, it can be on the exam.
>
>http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/np1_c/1
cprt1/1cindep.htm
>
>If you can't get to it, look to see if the url wrapped to the next line,
>it's rather long.
>
>Brian
>
> On Thu, 28 Dec 2000,
>Ronnie Royston wrote:
>
> > I have found that manupulating admin distance along with the passive
> > interface command is easier, albiet more 'dangerous'. Certainly, it takes
> > less commands for this method. The higher admin distance should be on the
> > remote routers, the lower on the core.
> >
> > -----Original Message-----
> > From: Connary, Julie Ann [mailto:jconnary@cisco.com]
> > Sent: Thursday, December 28, 2000 1:45 PM
> > To: ccielab@groupstudy.com
> > Subject: route-feedback, route-maps and mutual redistribution -
> > discussion topic
> >
> >
> > Hi All,
> >
> > I am noticing that solutions to many of the labs I am doing do not include
> > distribute lists
> > or route-maps to prevent route-feedback at mutual-redistribution points.
> > Doyle, in his
> > redistribution chapter (page 717) also does not use them but mentions on
> > page 769 that you should
> > always use them "any time a router is performing mutual-redistribution -
> > the mutual sharing of routes between two
> > or more routing protocols - route filters should be used to ensure the
> > routes are advertised in only one direction."
> >
> > so does anyone have any comments on this? Are you all using route-maps to
> > control redistribution at
> > mutual-redistribution points - like a router redistributing between ospf
> > and eigrp? Any rules of thumb to go by?
> > Sometimes it's a real pain to get setup and can cost you alot of time -
> > like why the defualt route is
> > not getting propagated.
> >
> > Thanks,
> >
> > Julie Ann
> > ------------------------------------------------------------------------
> > Julie Ann Connary
> > | | Network Consulting Engineer
> > ||| ||| Federal Support Program
> > .|||||. .|||||. 13635 Dulles Technology Drive,
> > Herndon VA 20171
> > .:|||||||||:.:|||||||||:. Pager: 1-888-642-0551
> > c i s c o S y s t e m s Email: jconnary@cisco.com
> >
> > ------------------------------------------------------------------------
> >
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