Anytime that you are going to be redistributing a protocol into another and then back into that originating protocol you are going to have potential for routing loops.
With that being said.....the exam is designed to test your understanding of the technology and if I were designing a scenario you can bet I would introduce potential for loops. In short....I would understand this technology backward and forward as this is fair game on the exam. As for real life applications, I am a systems engineer for a consulting firm and these scenarios come up quite a bit when you’re talking about redundancy within the topology. Think of it this way....even if you do not get redistribution with route tagging on the exam, it will make you a stronger engineer to fully understand the technology and disseminate how the router thinks. My two cents. Christopher Fata | 616.528.0660 | CCIE Written, CCNP, MCSE | [cid:[email protected]] | www.netechcorp.com<http://www.netechcorp.com> From: [email protected] [mailto:[email protected]] On Behalf Of Marko Milivojevic Sent: Friday, December 10, 2010 4:28 PM To: Carlos Valero Cc: CCIE_RS OnlineStudyList Subject: Re: [OSL | CCIE_RS] Route tagging with redistribution Carlos, You are very likely to find a scenario that is "best" solved using route tagging in your lab exam. -- Marko Milivojevic - CCIE #18427 Senior Technical Instructor - IPexpert FREE CCIE training: http://bit.ly/vLecture Mailto: [email protected]<mailto:[email protected]> Telephone: +1.810.326.1444 Web: http://www.ipexpert.com/ On Fri, Dec 10, 2010 at 12:00, Carlos Valero <[email protected]<mailto:[email protected]>> wrote: Hello, I have a general question about Route Tagging. Although the general idea seems pretty simple, the actual implementation can be VERY complex and it usually leads to BIG mess! So my question is: How likely are we to find Route Tagging Lab scenarios in the real CCIE Lab Exam? I had been told that it is very unlikely that we'll have to deal with it in the Exam. Is that true? Should I not pay too much attention to it and basically "gamble" on the possibility of NOT finding it in the real Lab Exam? How about real life? Does anyone really mess with these Tags in real life? Or is it a seldom use feature as so many obscure IOS features? I hope somebody can shed some light on this. Thanks!! --- On Mon, 11/2/09, Vikas Sharma <[email protected]<mailto:[email protected]>> wrote: From: Vikas Sharma <[email protected]<mailto:[email protected]>> Subject: [OSL | CCIE_RS] Route tagging and redistribution between an IGP and EGP To: "CCIE_RS OnlineStudyList" <[email protected]<mailto:[email protected]>> Date: Monday, November 2, 2009, 7:13 PM Hi Guys, I need your help out here. I have created a lab in GNS as follows: R0 - R1 - R2 - R3 all run EIGRP. R2 - R3 - R4 run BGP as well. R2 - R3 redistribute EIGRP into BGP and vice versa. I am attaching a zip file with the drawing plus configs and the NET file. The intention of this lab is as follows. 1. R0 and R1 simulate 2 client sites connected together. 2. We have a route map on each router that sets tags on routes that are not local to that particular site. 3. This route map is applied to a distribute list in the direction of routers R2 and R3 respectively. 4. I managed to get the EIGRP part working. 5. However, as far as tagging routes is concerned, for some reason R1 has stopped tagging routes to send them onwards to R3. It worked yesterday and not today and I wonder if this is a GNS thing. 6. On R2 and R3 there is another route map that looks for tags and then does an as-prepend to make tagged routes more expensive and send them to R4 which is like a remote site router. The idea is that BGP must see 2 paths which we influence, in its routing table and should one of the sites (either R0 or R1) goes off the air it should automatically be able to use the second path to reach that network. 7. When I apply the redistribute statement with the route map in BGP on routers R2 and R3, I find that the BGP routing table has only a few networks learnt and no alternative path. 8. I then took off the redistribute eigrp statement off the BGP config and re-added it in without the route-map and lo and behold, I see all the routes on R4 and each have an alternative path. Result is exactly as I want but I want to influence the routes in BGP. So, basically, if routes originating on R0 and seen on R2, the routing on R4 for those networks should be via R2 and not R3. Right now I'm not able to influence these routing decisions. However, without the route-map, it works beautifully but I want to use route tagging to influence how BGP decides where to route and have an alternative path. I look forward to your feedback. Cheers, -- Vikas Sharma Network Specialist Fujitsu Australia (M): 0421 052 117 -----Inline Attachment Follows----- _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com<http://www.ipexpert.com> _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com<http://www.ipexpert.com> CONFIDENTIAL NOTICE: This electronic transmission and any attachments constitute confidential information which is intended only for the named recipient(s) and may be legally privileged. If you have received this communication in error, please contact the sender immediately. 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