From: Joseph Brunner (joe@affirmedsystems.com)
Date: Wed Oct 24 2007 - 23:44:24 ART
Yeah, duh, I wasn't thinking (sorry happy hour)
I meant if we can't change AD for other reasons... If you give OSPF the
ability to detect external routes, the way eigrp does by default, you are
changing ad, yes?
I think if we tag every where we redistribute (as Scott V. mentioned Scott
M. said) it just makes sense... I actually do this in my IE WB labs, just to
get good at going to a router downstream and doing "show ip route x.x.x.x"
and looking at my tags, etc.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Joseph Brunner
Sent: Wednesday, October 24, 2007 6:51 PM
To: 'Herbert Maosa'
Cc: 'Jeffrey Biggs'; ccielab@groupstudy.com
Subject: RE: Redistribution with route tags are KILLING ME!!!`
Yes, but Herbert, what if all ospf routes are external that we are getting
feedback from
(i.e. the task wanted redistributed connected to ospf.)
Then we can't filter that way.
_____
From: Herbert Maosa [mailto:asawilunda@googlemail.com]
Sent: Wednesday, October 24, 2007 6:37 PM
To: Joseph Brunner
Cc: Jeffrey Biggs; ccielab@groupstudy.com
Subject: Re: Redistribution with route tags are KILLING ME!!!`
Actually, I use route-tags in two cases
* one of the protocols is already carrying external routes from
elsewhere
* one of the protocols is RIP, which has no concept of External routes
Except for these two cases, so far I successfullly implement loop free
redistribution by matching internal routes ( in the case of OSPF ) or
matching route-type Internal ( for the case of EIGRP ).
I think the use of route-tags is generally overused, perhaps overtrained, so
much so that you end up using it on every redistribution scenario without
understanding what you are trying to accomplish. Could waste quite a lot of
time at the best, and you could get it all wrong at the worst !
.
Herbert.
On 10/24/07, Joseph Brunner <joe@affirmedsystems.com> wrote:
Wait slow down...
You only NEED to use redistribution with route-tags when you have more than
1 router doing mutual route re-distribution. We use the tags to block route
feedback. That is, if a route has been redistributed already at either
router it wont be re-redistributed back to the source protocol at the other
router.
Here is an example... R3 and R4 are redistributing between EIGRP & OSPF. To
prevent a loop we don't allow route feedback from a protocol back into a
protocol. Anything going from OSPF to EIGRP, and EIGRP to OSPF is tagged and
the redistribution at other router denies routes with that tag before
redistribution. The tags allow us to know WHERE that route originally came
from.
Here is the topology
R1---OSPF--- R3--- EIGRP-AS-10--- R5
| |
R2---OSPF--- R4--- EIGRP-AS-10--- R6
R3&R4
Router ospf 1
Redis eigrp 10 subnets route-map watch-tag
Router eigrp 10
Redistribute ospf 1 route-map watch-tag metric 1500 100 255 1 1500
Route-map watch-tag deny 5
Match tag 5
Route-map watch-tag permit 10
Set tag 5
Try it with my topology in your dynamips...
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jeffrey Biggs
Sent: Wednesday, October 24, 2007 4:48 PM
To: ccielab@groupstudy.com
Subject: Redistribution with route tags are KILLING ME!!!`
I have been trying to grasp the use of redistribution using only route tags,
but I just keep getting killed by it. I can redistribute using prefix-lists
and ACL's all day long, but I know I am going to see something where I need
to "make sure all IP's are fully reachable without the use of
ACL's/Prefix-lists" and I am going go down in flames..Is there someone out
there that has a solution that can help me??????? I have used NMC and
IPEXPERT (BOTH VERY GOOD TOOLS, NOT KNOCKING ANY OTHERS) but my brain is
just not grasping the concept.
HELP!!!!!!!
Thanks
JB
This archive was generated by hypermail 2.1.4 : Fri Nov 16 2007 - 13:11:18 ART