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EIGRP OSPF Redistribution Sim

January 8th, 2019 in Lab Sim, LabSim Go to comments

Question

OSPF_EIGRP_Redistribution.jpg

Answer and Explanation:

First we need to find out 5 parameters (Bandwidth, Delay, Reliability, Load, MTU) of the s0/0/0 interface (the interface of R2 connected to R4) for redistribution :

R2#show interface s0/0/0

Write down these 5 parameters, notice that we have to divide the Delay by 10 because the metric unit is in tens of microsecond. For example, we get Bandwidth=1544 Kbit, Delay=20000 us, Reliability=255, Load=1, MTU=1500 bytes then we would redistribute as follows:

R2#config terminal
R2(config)# router ospf 1
R2(config-router)#
redistribute eigrp 100 metric-type 1 subnets
R2(config-router)#exit
R2(config-router)#router eigrp 100
R2(config-router)#redistribute ospf 1 metric 1544 2000 255 1 1500

Note: If the delay is 20000us then we need to divide it by 10, that is 20000 / 10 = 2000

Note: “usec” here means microsecond (which is 1/1000 milliseconds). According to this link: http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094cb7.shtml#eigrpmetrics: “The delay as shown in the show ip eigrp topology or show interface commands is in microseconds”)

For R3 we use the show interface fa0/0 to get 5 parameters too

R3#show interface fa0/0

For example we get Bandwidth=100000 Kbit, Delay=1000 us, Reliability=255, Load=1, MTU=1500 bytes

R3#config terminal
R3(config)#
router ospf 1
R3(config-router)#
redistribute eigrp 100 metric-type 1 subnets
R3(config)#
exit
R3(config-router)#
router eigrp 100
R3(config-router)#
redistribute ospf 1 metric 100000 100 255 1 1500

Finally you should try to “show ip route” to see the 172.16.100.1 network (the network behind R4) in the routing table of R1 and make a ping from R1 to this network.

Note: If the link between R2 and R3 is FastEthernet link, we must put the command below under EIGRP process to make traffic from R1 to go through R3 (R1 -> R2 -> R3 -> R4), which is better than R1 -> R2 -> R4.

R2(config-router)# distance eigrp 90 105

This command sets the Administrative Distance of all EIGRP internal routes to 90 and all EIGRP external routes to 105, which is smaller than the Administrative Distance of OSPF (110) -> the link between R2 & R3 will be preferred to the serial link between R2 & R4.

A reader on our site has a closer explanation for the “distance eigrp 90 105” command so we quote it here for your reference:

The “distance” refers to the administrative distance of the routes provided by a given routing process. By default, internal (which means non-redistributed) EIGRP routes are given an administrative distance of 90 while external (redistributed from another routing process) EIGRP routes are given an administrative distance of 170. The default administrative distance of OSPF is 110. The administrative distance measures the “distance from the truth” and tells the router which routes are more trustworthy. Lower administrative distance = more trustworthy. For this reason, connected routes have an administrative distance of 0. They are the MOST TRUSTWORTHY, because they are physically connected to the router. When making a decision about which route to install in the routing table, the router looks at administrative distance first. The metric (or cost) is only considered if two routes have the same administrative distance.

In this case, R2 will learn about R4’s loopback network from both R4 and R3. The route from R4 will be in OSPF (admin distance of 110) because R2 is also running OSPF while the route from R3 will be an external EIGRP route (administrative distance of 170 by default). Since the OSPF route has a lower administrative distance, it will get placed in R2’s routing table and the R3-provided route will be ignored. This is not optimal, since the path through R3 is a faster, more reliable path. To fix this, we change the administrative distance of external EIGRP routes at R2 by using the “distance eigrp 90 105” command. This sets the administrative distance of internal EIGRP routes to the default of 90 and changes the administrative distance of external EIGRP routes to 105 (less than that of OSPF routes). Now, when R2 learns of the loopback network from R4 and R3, it will install the now lower administrative distance external EIGRP route from R3 and our traffic from R1 will take the faster path.

Note: Please check the OSPF process numbers first before typing these commands.

If you want to have a closer look at this sim and understand more about the “distance eigrp” command, please read my OSPF EIGRP Redistribute Lab in GNS3.

Other lab-sims on this site:

EIGRP Stub Sim

OSPF Sim

IPv6 OSPF Virtual Link Sim

EIGRP Simlet

Policy Based Routing Sim

Comments
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  1. Anonymous
    August 27th, 2019

    Hi, anyone with the latest CCNP 300-101 dumps?

  2. ano
    September 4th, 2019

    why we do it on R2# distance eigrp 90 105 ? shouldn’t we do it on R3?

  3. HKpirate
    September 5th, 2019

    Because one of the question requirement is:
    ” All traffic must use the shortest path that provides the greatest bandwidth.”

    OSPF route AD is 110 and Eigrp ext. route is 170 ( default)

    if not change , it will go by R1-R2-R4 that not meat the question requirment.

    So, change the Eigrp ext. AD to 105. ( or smaller than OSPF 110 ) to make it select route to R3 .

    So the path = R1-R2-R3-R4

  4. RG
    September 7th, 2019

    This question was in my exam with a small change the delay for R3 fastethernet was 100 and not 1000 as this example, the rest was the same.

  5. User42069
    September 18th, 2019

    I’ve done the CCNP route two times in which this question came 2x along. For some reason I can’t answer this question.

    Why is it that you have to use the command ospf 1 and not ospf 24 /34 since that is the area ID and thus the Process ID?

    Also you can enter R4 as well for some reason.

  6. Anonymous
    September 18th, 2019

    @user42069

    OSPF process ID is different from OSPF area ID.

  7. Nomi
    September 26th, 2019

    Hi All i am just going for this exam after 2 days is there any update so please share, Advance thanks

  8. anone
    September 30th, 2019

    what if I use different process id on R2 & R3? will I still get a perfect mark?

  9. KKnw
    October 5th, 2019

    Hi ALL;

    1) Do we really need to calculate BW; Delay in Exam from interfaces or will be given directly.
    2) Did more question comes on IPv6

  10. ppk slb
    October 13th, 2019

    Guys, a friend of mine took Route today and passed; for some labs, copy run start/wr works, while some does not (involved config change). If it does not work, you marks won’t get deducted (as they meant the exam to be like that). ‘Pipe’ does not work. Thankfully ‘tabbing’ works. For some commands that does not work, you have to find another way to verify (sh run etc – Cisco did this to ensure you know how to verify thru configs instead of IOS command). There’s one command ‘sh ip eigrp topology’ does not work, but ‘sh ip eigrp 1 topology’ works. So please state the process id if it does not work. He said labs are fine, the objectives quite hard.

    Below is his comments;

    THANKS EHAB/DIGITALTUT; DUMP VALID

    But please do not memorize dumps cause some questions they changed something – please ensure u understand it.

    If some commands does not work and you were not meant to use it, the error message will say ‘Command not implemented etc…’ when you executed the IOS command.
    There’s always another way to verify/troubleshoot it (sh run etc…)

    13th Oct; Passed with 839/1000

    LAB EXAMS:
    ———-

    EIGRP Evaluation Sim – comments below;
    —————————————-
    -command ‘sh ip route’ on R6 does not work; i can only do ‘sh run’
    -why do i need to use ‘sh ip route’? Because there’s 2 loopback configured at R6, i need to know
    which one should i choose
    -so i guess Cisco purposely disable it to make my life hard; they want us to verify routing via configs
    -from ‘sh run’ at R6, i can see that 172.16.6.6 is configured, but it was not advertised out because there’s
    ‘distribute-list 1 out’ being configured, where the ACL denied loopback IP 172.16.6.6.
    -another simpler way to verify is that ‘172.16.6.6’ loopback is not shown in R1 routing table (sh ip route); thus we can say that loopback ip that we should use is 150.1.6.6
    -another thing to take note is that ‘show ip eigrp topology’ command does not work in R1 (not sure on other router, i haven’t tested it out) – per suggested on Digitaltut, we should use the EIGRP process ID. Then it works like charms. I’ve executed ‘sh ip eigrp 1 topology’ and it works. Luckiliy i read this part from Digitaltut. However, if this happens and you don’t have any idea on this, i guess ‘tab’ or ‘tabbing’ will give you an idea (tabbing works in Exam labs)

    OSPF Sim – comments below;
    —————————
    -everything the same except the IP. no surprises here. easy.
    -tabbing works, and copy running-config startup-config works. I did ‘wr’ command too and it works.

    IPv6 OSPF Virtual Link Sim – comments below;
    ——————————————-
    -copy run start/copy running-config startup-config/wr does not work – so just ignore it (you marks won’t get deducted)
    -everything is the same
    -in this scenario, i can see the loopback ip from R1 after added and remove virtual links, so i don’t have to make any changes on the
    loopback ip (that has to be in area interfaces)

  11. ppk slb
    October 15th, 2019

    who needs updated dump for ROUTE can contact me: philipsmeloo @ gmail. com

  12. pacman
    October 18th, 2019

    please tell me. Why metric type is 1?

  13. Anonymous
    October 27th, 2019

    Yeah I don’t think the metric type actually matters in this case…

  14. Anonymous
    October 28th, 2019

    Regarding the redistribution lab, why does it matter if the link between R2 and R3 is ethernet vs serial? Even when R2 to R3 is serial the path from R1 -> R2 ->R3 ->R4 has the most bandwidth. Even then it still doesn’t matter because if R1 -> R2 is serial then the traffic is bottlenecked. Someone in the comments said their version of the SIM had all ethernet links except for R2 -> R4 which would make the most sense. Can anyone confirm?

  15. Anonymous
    October 29th, 2019

    so we only adjust eigrp distance when there is fast link between r2 and r3 ?

  16. Anonymous
    October 31st, 2019

    Shouldn’t we also use route tags when redistributing? I mean, it’s a Cisco best practice to prevent redistributed routes from being redistributed again into the same routing domain. You can add a tag when redistributing from let’s say OSPF into EIGRP and then filter that same route when redistributing from EIGRP into OSPF by matching on the route tag applied earlier.

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