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EIGRP OSPF Redistribution Sim

January 8th, 2015 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

(Notice: In fact, these parameters are just used for reference and we can use other parameters with no problem. Also, a candidate said that the simulator didn’t accept the Bandwidth of 1544; in that case, we can use a lower value, like 128.

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

Note: “usec” here does not mean microsecond (which is 1/1000 milliseconds) but means millisecond. In short usec = msec. I don’t know why they use the word “usec” here but just think it is “msec” (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=10000 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 10000 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. Shri
    February 21st, 2018

    Hi guys any latest dumps for 300-101.

    my exam is in next month.

    this is my email id :- shriramtrimal19 at gmail dot com

    thank you

  2. ccnp83
    March 5th, 2018

    Hi digitaltut,

    im one of your premium members.I have a very confusing situation if you could help please,i have my exam booked for tomorrow.

    Im struggling to understand the EIGRP Redis Lab.

    Digital have presented two scenarios,one wiht serial and another with fast ether link between router 2 and router 3.

    The confusion is show command you are displaying.

    In one scenario,its the interface in the OSPF domain towards r4 from where you are gathering the BW Delay and MTU stats
    and the serial interface between r2 and r4 is also used for the BW and DElay stats.

    In contrast,another scenario when the link between the r2 and r3 is fasthethernet,you are using the show interface for the fast Ethernet link between r2 and r3 and not sticking to the original interfaces you used in the first scenario.

    How do i know why you have used two different interfaces for two different cases.

    In case 1 and case 2,both the interfaces should be the ones used in the ospf domains?

    In case 1 you are using OSPF facing interfaces for EIGRP metric where as in case 2 you are using the EIGRP facing interfaces to get the stats.please explain.

  3. teosoup
    March 22nd, 2018

    Hi gus ,

    Could you please someone explaine to me why traffic from R2 – R3 is redistributed,
    (based on above documentation)

    It should be internal eigrp AD=90,

    thanks

  4. chuks
    April 3rd, 2018

    why do we need to use both metric type 1 on both asbr. One could be specified metric type 1 while the other will be a type 2 by default., ospf will prefer the metric type 1 by default which leaves the serial link less preferred.

    someone reply me but I don’t see both metrics as type 1 as to be mandatory.

  5. cisco breaker
    April 11th, 2018

    Hey friends, who took the exam recently? the labs are still:
    PBR
    Redistribution
    OSPF
    EIGRP
    OSPFv3

    ??

    Appreciate the help.

  6. airon
    April 13th, 2018

    Hello,

    Why are they using metric-type 1 instead of redistribute eigrp 100 subnets??? I don’t get it

    router ospf 1
    R2(config-router)# redistribute eigrp 100 metric-type 1 subnets

  7. Elv
    April 16th, 2018
  8. airon
    April 18th, 2018

    @elv thanks for sharing the link. Now I understand the reason of using metric-type 1

  9. e-coup
    April 19th, 2018

    Hello, what is the difference for case1 and case2?
    i see the distance command, but for me looks like we should use it in both cases

  10. Toby
    April 19th, 2018

    I don’t think that you’re required to use the distance command in the sim. The guy tried to go extra mile to show you how you can dictate/control which path you should go thru to get to router 4.

  11. Jpar
    April 23rd, 2018

    Can anyone please send me the latest 300-101 dump to me ?
    jigar231@gmaildotcom

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