EIGRP Summarization


The owner of this network has been complaining about performance issues for awhile. You as the junior network engineer have just learned about summarization and the possible advantages this might bring to your network. It’s up to you to bring summarize the networks and bring the glory back to the routers…


  • All IP addresses have been preconfigured for you.
  • EIGRP AS123 has been preconfigured for you and is advertising all networks.
  • There are plenty of loopbacks with IP addresses configurated for you to summarize.
  • You are not allowed to use EIGRP auto-summarization.
  • Ensure router Cole and Santiago only have a single /21 entry in their routing table.
  • Ensure router Fenix will send traffic for towards router Santiago. Do not change the Administrative Distance or Metric(s) to achieve this.
  • Ensure router Fenix only sees 2 entries for the network range. /22 and /22.
  • Further summarize the /22 and /22 network so router Fenix and Cole only see the /19 entry in their routing table.
  • Advertise a default route on router Cole towards router Fenix, you are not allowed to use the default-network command.

It took me 1000s of hours reading books and doing labs, making mistakes over and over again until I mastered all the protocols for CCNA.

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You will learn all the secrets about EIGRP, summarization and more.

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Video Solution:

Configuration Files

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Written by René Molenaar - CCIE #41726

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About the Author: Rene Molenaar

René - CCIE #41726 is the creator of GNS3Vault.com where he shares CCNA, CCNP and CCIE R&S labs. He also blogs about networking on http://networklessons.com


  1. – summarize on f1/0 & f0/0
    FENIX(config-if)# ip summary-address eigrp 123 90
    – either static route(cheat) or tune bandwidth (not cheat)
    FENIX(config)#int f1/0
    FENIX(config-if)#bandwidth 10000
    could block route from entering FENIX at f1/0 with a route map + distribute list, denying routes for from
    – On Santiago configure on f0/0 & f1/0
    Santiago(config-if)#ip summary-address eigrp 123 90
    Santiago(config-if)#ip summary-address eigrp 123 90
    -remove last config & on f0/0 & f1/0 on Santiago
    Santiago(config-if)#ip summary-address eigrp 123 90
    – just add static default route EIGRP should distribute it fine
    COLE(config)#ip route l0
    you can block this out of f1/0 to ensure route is propagated in one direction
    COLE(config)#ip access-list standard BLOCK
    COLE(config-std-nacl)#permit any
    + apply in eigrp
    COLE(config-router)#distribute-list out BLOCK f1/0

  2. Hi Oliver,

    You can finish this lab by using summaries only, no need for distribute-lists, route-maps, access-lists and so on.

    I have the solution for this one on Youtube but I didn’t add them to the site yet. If you want to see it check my youtube channel (youtube.com/gns3vault) or wait 24 hours and i’ll make sure it’s here.


    1. please write “sh ip route eigrp” instead “sh ip route”

  3. Rene,

    I am missing something here.

    Why did router Fenix placed ‘D [90/158720] via, 00:00:11, FastEthernet0/0’route after receiving ‘ip summary-address eigrp 123’ from router Cole?

    Thank you.

  4. Hello Dmitri,

    Routers will always prefer [b]most specific prefixes[/b].

    When we configure a summary on router Cole on the FastEthernet0/0 interface it will no longer advertise It will still advertise this prefix through it’s FastEthernet1/0 interface.

    Router Fenix will learn a more specific prefix ( from router Santiago and will use this path.

  5. i went the opposite direction to achieve the objective and by only configuring summarization and static routes on router santiago. i come to like EIGRP alot.. its flexible and fast.

  6. when i downloaded th ZIp file why the pre-configuration is missing?

  7. Nice Job Rene

    Regarding your step 6 "[i]Ensure router Fenix will send traffic for towards router Santiago. Do not change the Administrative Distance or Metric(s) to achieve this.[/i]"

    I found another solution which I want to share with you.
    On Router FENIX I did the following:

    [b]access-list 150 permit ip host host[/b]
    It is a trick by using and extended ACL as a prefix list.

    Then applied a distribute list
    [b]distribute-list 150 in FastEthernet1/0[/b]

    If we look into routing table we see:

    [b]FENIX#show ip route eigrp[/b] is subnetted, 1 subnets
    [b]D [90/158720] via, 00:19:20, FastEthernet0/0[/b] is variably subnetted, 9 subnets, 2 masks
    D is a summary, 00:31:06, Null0 is variably subnetted, 3 subnets, 2 masks
    D [90/156160] via, 00:08:38, FastEthernet0/0
    D [90/156160] via, 00:04:47, FastEthernet0/0
    D [90/156160] via, 00:06:51, FastEthernet0/0
    D [90/30720] via, 00:19:20, FastEthernet0/0

    Which is what we want.

    And a traceroute show us:


    Type escape sequence to abort.
    Tracing the route to

    1 0 msec 0 msec 8 msec
    2 4 msec 8 msec *

    Which is the alternate path towards router Cole.
    But this is more complex approach. In addition, I like your approach because you used prefix longest match 🙂



  8. For forwarding traffic, you can also solve it by adjusting the Bandwidth of F1/0 in both fenix and Santiago.

    1. Yeah, but one of the constraints in the lab is that you can’t change metrics.

  9. I was able to change the traffic to through santiago by configuring a distribution-list or offset-list. Using the offset-list, I increased the FD towards Fenix from Cole. I used the distribution-list to filter the route out towards Fenix. 🙂

    Nice labs

  10. After needing to brush up on a lot of thigs I am finding this and many of the Tutorials on your site excellent. As well as the ebooks !!

    [b]Thanks heaps mate[/b]

  11. Hi Rene

    When i use a summary for with mask on Fenix Fa0/0 and 1/0

    I look at Core and Santiago i am still getting the /16 auto summary do you know why

  12. I configured summary for on cole router fa0/0 but now router fenix is loadbalancing it.

  13. Hello Rene,

    I got problems with paragraph:
    Ensure router Fenix only sees 2 entries for the network range. /22 and /22.

    It’s quite easy to achieve it, if we also assume that the same entry will appear on router COLE, by adding:

    ip summary-address eigrp 123
    ip summary-address eigrp 123

    on both, Fa0/0 and Fa1/0 interfaces. But how to do the same for only FENIX router (without adding those entries on COLE router)?

    1. it doesn’t say only Fenix, it says Fenix only sees 2 entries!!!
      we have to pay attention to the wordings…

  14. can’t start the routers 🙁
    DynamipsError: 208-unable to find object ‘R3’
    Any suggestions please
    I am really enjoying the labs from here.

  15. COLE#sho ip route
    Codes: C – connected, S – static, R – RIP, M – mobile, B – BGP
    D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
    N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
    E1 – OSPF external type 1, E2 – OSPF external type 2
    i – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2
    ia – IS-IS inter area, * – candidate default, U – per-user static route
    o – ODR, P – periodic downloaded static route

    Gateway of last resort is to network

    D [90/30720] via, 00:21:27, FastEthernet1/0
    [90/30720] via, 00:21:27, FastEthernet0/0
    C is directly connected, FastEthernet0/0 is subnetted, 1 subnets
    C is directly connected, Loopback0 is subnetted, 1 subnets
    D [90/156160] via, 00:13:28, FastEthernet0/0 is subnetted, 1 subnets
    D [90/156160] via, 00:00:53, FastEthernet1/0
    C is directly connected, FastEthernet1/0
    S* [1/0] via


    I still hate route summary

  16. For advertising, I instead revamped the network into it’s individual matching networks on each interface, and used “network”.

    Like others, I used access-lists and distribute lists to meet the next goal, but I do understand the “most specific route wins” idea when using summary-address to get your results.

    For summarizing the and networks, I modified the network commands with wildcard masks again, and then used the summary-address interface commands to summarize it down to a after that.

    I didn’t realize you meant for us to only use summarization commands to do it all. Ah well….

  17. I have the 3620 image. Will this work for the configs that cna be download or do you need the 3640 image?

    1. I think it’s best to stick to the 3640 image. If you use another image, you’ll have to edit some of the topology.net files and I’m not sure if the interface numbering is the same.

  18. Hello Rene, Et al,

    id like to say thank you for making these labs, i enjoy them way more than reading the text books.

    my question is could you or anyone please give me the list of loop-backs and masks for each router? i have not been able to load any of the configs into GNS3 since the start of ospf so i have been building my topologies from scratch by watching the videos and looking at the topology diagram but no so easily with this lab. please help



  19. Hi Rene,

    For the last task i used a static default route on COLE and redistributed into the EIGRP process. What is your opinion about that?

  20. Sorry if someone else has already commented on this as i haven’t checked but did you realise that the final config file for this links to the startup config zip file.

    I don’t requrie it thanks but just thought it was worth mentioning. Thanks for all your labs they have been invaluable in my efforts to keep my practise in.

  21. Santiago#sh ip rou eigrp
    D [90/30720] via, 00:01:00, FastEthernet1/0
    [90/30720] via, 00:01:00, FastEthernet0/0 is variably subnetted, 2 subnets, 2 masks
    D [90/156160] via, 00:01:00, FastEthernet1/0
    D [90/156160] via, 00:01:00, FastEthernet1/0 is variably subnetted, 9 subnets, 2 masks
    D is a summary, 00:01:02, Null0
    I had do ip summary address on both the interfaces why i get

    I use summary address on both the interface why I get this

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