Recently the australian government has decided that every major City should be interconnected. So far different states have used their own routing protocol and some of the older hardware is unable to run OSPF. Government workers have connected all routers and configured redistribution between RIP and OSPF so that every network is reachable. Everything seems to work fine and all routing tables have full information, however some people complained that the network is slow. You notice that when you start a traceroute from router Sydney or Melbourne towards the networks behind router Adelaide (4.4.4.4) or Darwin (5.5.5.5) that the traffic is sent towards router Perth. This is a classical example of sub-optimal routing...up to you to improve things!
Goal:
All IP addresses have been preconfigured for you as following.
Every router has 1 loopback interface as following: Loopback0: x.x.x.x /24 for example: 1.1.1.1 for router1.
RIP and OSPF are preconfigured for you.
Do not use show run! (this will spoil the fun :) use the appropiate 'show' and 'debug' commands. This will teach you the skills needed to become a true troubleshooting master.
Do not make changes to the network commands in OSPF or RIP.
You are not allowed to use distribute-lists, prefix-lists or route-maps.
You are not allowed to change any of the redistribution commands.
Ensure traffic takes the most optimal path to it's destination, use traceroute to check this.
Ensure all routers have full connectivity, every network should be pingable using the most optimal path.
It took me 1000s of hours reading books and doing labs, making mistakes over and over again until I mastered all the troubleshooting issues for CCNP.
Would you like to be a master of troubleshooting too? In a short time without having to read 900 page books or google the answers to your questions and browsing through forums?
I collected all my knowledge and created a single ebook for you that has everything you need to know to become a master of troubleshooting.
You will learn all the secrets about redistribution, solving routing loops, sub-optimal routing and more.
If you check the routing table you'll see that the OSPF routes are preferred over the RIP routes since they have an AD of 110 compared to rip which is 120.
So to make sure that the router prefers the RIP routes you need to make sure that whatever you redistribute INTO OSPF has a higher AD than RIP.
This will make sure that the original RIP routes are preferred over the injected OSPF routes.
Hopefully this will help you, i'll record a video for this one.
If you change the AD you will still have some problems. Let's say you reduce the AD for rip from 120 to 100, which is lower than OSPF (110).
Router Sydney will redistribute it's 192.168.24.0 network into OSPF. Router Melbourne will redistribute this network again into RIP with a hop count of 1.
What do you think Darwin will do when it wants to reach the 192.168.24.0 network?
Redistribution is one of the hardest things to do with routing, playing with the AD is one way to fix things though...but it's part of the solution.
I'll try to add a video for this one soon, but let me give you some hints to think about:
- What if the AD for external prefixes was higher than internal prefixes?
- Should routes from RIP into OSPF be redistributed again into RIP? (or vice versa)
- What happens with router Melbourne and Sydney if they receive OSPF prefixes that originally came from the RIP network?
Gideon Girigiri2011-06-02 05:26:48
well this is splitting my head in two!. I've only done the "CCNA 1" course. so this is kind of beyond me. but i would really love to see how you solve this problem.
but if the problem happens to be on RIP having a hop count of 1, after redistribution. depending on which path it takes the packet will be dropped by the destination router. this I'm sure you already know. now what i want to know is, could we put a multihop command into RIP to fix that problems? I've played with internal and external BGP a bit and that seems to fix the problems I've had from using different AS. I'm not sure if that would make any difference to the problem at hand, I'm just throwing the idea out there.
as for your external AD prefix I'm a bit confused. from my understanding if a external protocol was introduced to another routing protocol in most cases the external prefix will always have a higher AD, meaning that the internal protocol will take charge over the external... so to answer your question if the external was higher than the internal, the internal would come still first in the routing table.
Gideon Girigiri2011-06-02 05:32:16
I'll just wait for the video to come out and see how you solve the problem. sorry if I've wasted your time but I'm just a bit interested in networking and just felt like partaking in the conversation. oh and i just notice this is a CCIE level lab. ouch sorry!!
Redistribution is complex...and if you did your CCNA this will be a bit mind boggling Redistribution is on the CCNP btw. Only EIGRP has a different AD for internal and external prefixes. OSPF makes a different between internal prefixes or externals but does not have a different AD (you can change that though). RIP has the same AD for everything but we are able to manipulate this.
I'll try to upload the video soon, i'm working my way through all the labs...top to bottom recording all of them.
Gideon Girigiri2011-06-02 19:13:14
well, your right redistribution is hard, I've tried doing it many times and failed. but since my summer course was canceled I'm planing on buying a CCNA/CCNP router set. and do some self studying this summer, and hopefully I'll to know more about the process. I'll stop posting on the blog now since I'm not at the level to understand this yet. thank for replying by the way.
and i'll watch the video of it when u bring it out
No worries...trying to tackle stuff that's too high level is not a bad thing...aim for the moon and you miss you will at least end up amongst the stars!
I don't know what you do or do not know but these are the things you need to understand very well before you dive into redistribution:
- OSPF / EIGRP / RIP: Understand each routing protocol, how they make a difference between internal/external routes.
- Administrative distance: What it does and how to manipulate it.
- Most specific match.
I'll have this one online in a few days.
Gideon Girigiri2011-06-02 22:24:46
i already know how to set up the basic for those three protocols and i know the AD by heart now. but im sure there are more things that i still need to learn. i was trying to look for your email but couldnt find 1. i just have a few question i want to ask. i rly don't want to take up time asking them here... so if its possible, i would like to email please, if not i understand, and thanks for the lesson i'm looking forward to study this when i get to my CCIE level.
Let me ask you a question about changing the AD of RIP to 100.
- The loopback of router Perth is advertised into OSPF.
- This loopback network is redistributed from OSPF to RIP on router Sydney.
- Router Sydney advertises this RIP route to Adelaide.
- Router Adelaide will advertise it to Darwin.
- Router Darwin will advertise it to Melbourne.
What will happen to the routing table at router Melbourne? And will this cause a problem yes/no ?
@Taras setting the OSPF external routes to a higher AD is always a very good idea. It's the same as EIGRP does (90/170 for internal/external routes). It will ensure that external routes are never preferred to RIP because of the higher AD.
Good job, it's good to know multiple ways of solving a problem
Hi
Assuming that the definition of "most optimal path" is the fewest hops of routers in the transit path
I have 2 questions to the solution of this lab
-1-
wouldn't we have to exclude the 2.2.2.0/3.3.3.0 routes from the access-list of Sydney and Melbourne
because the most optimal path is through OSPF (not RIP) ??
-2-
Perth will have 2 equal-cost paths to these routes.(Each through Sydeney and Melbourne)
192.168.24.0/24
192.168.35.0/24
192.168.45.0/24
4.4.4.0/24
5.5.5.0/24
I think we have to tune the metric of these routes in order to use ONLY the most optimal path.
My solution to this was to create a route-map and attach it to the redistributing routers.
(example for Sydney)
----
redistribute rip metric 10000 metric-type 1 subnets route-map METRIC_11000
route-map METRIC_11000 permit 10
match ip address prefix-list NOT_OPTIMAL
set metric 11000
route-map MERIC_11000 permit 20
ip prefix-list NOT_OPTIMAL seq 5 permit 192.168.35.0/24
ip prefix-list NOT_OPTIMAL seq 10 permit 5.5.5.0/24
----
But the rule of the lab states that we aren't allowed to use a route-map nor change the statement of the redistribution.
Is there a solution to this by not breaking the rules??
Thanks , I really love your lab.They are awesome!!
Hello Rene, in your solution the loopbacks of the redistibution partners are not optimal reached. They should be reachable via OSPF Path. here my solution:
Thank you for the lab but I have questions about the solution.
1. You made an access list and changed the AD for the routes.
Is it simpler to enter the command "distance ospf external 130" for example?
2. After that the router Perth will have two routes for the destination in Rip domain which is also suboptimal routing on my opinion. It happens as the routes from RIP redistributed into OSPF with the same metrics.
I changed the redistribution command on Sidney and Melbourne using route-maps.
Redistribution is on the CCNP btw. Only EIGRP has a different AD for internal and external prefixes. OSPF makes a different between internal prefixes or externals but does not have a different AD (you can change that though). RIP has the same AD for everything but we are able to manipulate this.
