EIGRP Variance Command Example

(Rene Molenaar) #24

Hi Christopher,

Thanks for the heads up. I decided to get rid of the dots, might be less confusing :slight_smile: Over here we use commas, in the US they use dots. Might be easier to use nothing.

Rene

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(Christopher S) #25

Rene,

Oh, and I passed ICND2 on the 16th to get my CCNA R&S!! Thanks for all the good information that REALLY did help!! The stuff on spanning-tree and RPVST in particular was helpful.

Chris

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(Maher H) #26

Hi Christopher,

On behalf of Rene, we congratulate you to become CCNA certified & thanks for your kind words about our lessons.

Now it is time for CCNP R&S, right?
You can start with the ROUTE course hoping that soon you will be CCNP certified too.

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(Christopher S) #27

I think I’m going to go for CCNA Security next. Any good content on here for that cert? Going to work on CeH in the meantime, too. Thanks again!!

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(Maher H) #28

Hi Christopher,

Going to CCNA Security is a new decision.
In the website there is a course for ASA firewall which is from CCNP security level, but there is a plan to put CCNA security lessons somewhere in the future.

Good luck with your study.

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(Shantel - Networklessons.com) split this topic #29

19 posts were merged into an existing topic: EIGRP Variance Command Example

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(christopher w) #30

Rene,

i was working on the lab for myself. i have the exact same config. however my ports are different as i am using a different ios version router. my traceroutes would go from r1>r4>r5> where the 5.5.5.5 was at.

after taking down a link i would get this output. what does this traceroute mean (below)

Type escape sequence to abort.
Tracing the route to 5.5.5.5

1 192.168.12.2 108 msec
192.168.13.3 88 msec
192.168.12.2 44 msec
2 192.168.35.5 112 msec
192.168.25.5 72 msec
192.168.35.5 120 msec

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(christopher w) #31

forgot to mention that i took down the link from r1 to r4

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(Lazaros Agapides) #32

Hello Christopher

The output of your traceroute command is not quite clear. The format of the output should be something like this:

Router1#traceroute 34.0.0.4 

Type escape sequence to abort. 
Tracing the route to 34.0.0.4 

  1 12.0.0.2 4 msec 4 msec 4 msec 
  2 23.0.0.3 20 msec 16 msec 16 msec 
  3 34.0.0.4 16 msec *  16 msec 

Can you resend the output exactly as it was displayed in your command line? Thanks!

Laz

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(christopher w) #33

my mistake. i found the issue. thank you for your quick response. layer 8 issue. lol

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(Gregory L) #34

I found a typo in this lesson. The FD of R3 should be 412160, but was written 412.60.

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(Rene Molenaar) #35

Thanks @dinolystra, just fixed it.

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(rahul s) #36

Hello Rene

I followed all the step but still see some issue in traceroutes .I guess if the destination is 5.5.5.5 and we are load balancing we have 2 path via R2 & R3 .why do I see both R2& R3 ip in the traceroute .

## traceroute :
R1#traceroute 5.5.5.5

Type escape sequence to abort.
Tracing the route to 5.5.5.5

  1 192.168.13.3 64 msec
    192.168.12.2 64 msec
    192.168.13.3 64 msec
  2 192.168.25.5 60 msec
    192.168.35.5 64 msec
    192.168.25.5 60 msec
R1#sh clock
*14:34:04.131 UTC Sat Aug 19 2017



R1#traceroute 5.5.5.5 source 192.168.13.1

Type escape sequence to abort.
Tracing the route to 5.5.5.5

  1 192.168.12.2 64 msec 60 msec 64 msec
  2 192.168.25.5 88 msec 64 msec 68 msec
R1#traceroute 5.5.5.5 source 192.168.12.1

Type escape sequence to abort.
Tracing the route to 5.5.5.5

  1 192.168.12.2 36 msec 64 msec
    192.168.13.3 68 msec
  2 192.168.25.5 92 msec
    192.168.35.5 64 msec
    192.168.25.5 60 msec
R1#traceroute 5.5.5.5 source 192.168.13.1

Type escape sequence to abort.
Tracing the route to 5.5.5.5

  1 192.168.13.3 64 msec
    192.168.12.2 76 msec
    192.168.13.3 80 msec
  2 192.168.25.5 92 msec 60 msec 72 msec
R1#sh clock
*14:34:54.827 UTC Sat Aug 19 2017
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(Lazaros Agapides) #37

Hello Rahul

This is normal behaviour of traceroute when you have two equal cost routes. Traceroute sends ICMP packets and since both routes are equal, it will send them via both routes.

So for your first attempt, you get the following:

Note that for the first hop, indicated by the number 1, it shows three lines. The first is the first choice, the second is the second choice and the third is the actual route that was chosen between the two. So for the first hop, 192.168.13.3, or R3 was chosen as the route.
The second hop, indicated by the number 2 also has two options, because both routes via R2 and R3 were used and there are two options to choose from once again. So either Fa 0/0 or Fa1/0 of R5 will be used as the next hop. We are told in the third line that 192.168.25.5 or Fa0/0 is used.

In the next case, you are explicitly stating that you want to use interface E1/0 or IP address 192.168.13.1 as the traceroute source:

Because you are stating this, there is no option of using the load balancing capabilities of EIGRP so only one option is indicated in each case.

Now having said all of this, if the route via R2 and R3 from R1 were UNEQUALLY load balanced (using the variance command), this wouldn’t occur. Only one option would be displayed and used. You would only see one choice for each hop. The multiple choices for each hop indicate that there is EQUAL load balancing between the R2 and R3 routes. So you should check your configuration and make sure it is load balancing UNEQUALLY using the variance command.

I hope this has been helpful!

Laz

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(blue p) #38

Hi,

I would like to know if you need to configure variance on R1 and R5 for the return traffic? I believe if you need to reach the network 5.5.5.5 from R1, variance needs to be configured on R1. But how about the return traffic of the packet? I believe this will only use the successor path going back, is that right?

Thanks,

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(Lazaros Agapides) #39

Hello Blue

When implementing variance on a router, it ONLY affects the routing of that specific router. Therefore you are correct. If you want to adjust the routing behaviour of returning traffic, then you must implement variance on R5 as well.

In general, if you want to influence the routing behaviour of a specific device using the variance command, it only affects the way that specific device routes packets.

I hope this has been helpful!

Laz

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(Jeff H) #41

Hi I was studying use of the ‘variance’ command when I noticed the following:

Feasible Distance of R3 (feasible successor) = 41260
I assume it should read 412160 - I’m aware it is a very minor point, but it might cause a little confusion to some people.

regards
Jeff

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(Lazaros Agapides) #42

Hello Jeff

Thanks for picking that out! I will let @ReneMolenaar know to make the correction.

Laz

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(Juan C) #43

thank you for this excellent explanation…
So, for an eigrp route to be installed on the rib, it must first meet the feasibility condition (RD (reported distance or advertise distance) of the feasible successor < Feasible distance of the successor) and then it’s FD must be < Succesor’s FD * Variance integer
For example, if a Feasible Successor has a RD > FD of Succesor (doesn’t meet the feasibility condition) it wont never be installed on the rib… despite it’s FD < Succesor’s FD * Variance integer… thats right ?

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(Lazaros Agapides) #44

Hello Juan

Yes, that is correct. If the feasibility condition is not met, then the route will not be installed in the RIB and will not be a candidate to be used in a load balancing scenario.

I hope this has been helpful!

Laz

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