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Cisco website Error

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Feb 19th, 2014
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On the Cisco page of EIGRP, it totally leaves out the formula/explanation for where it got the REPORTED Distance from.



In this case, it's 307200.



This is very frustrating because it seems no matter what source material I use, things are left out.

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joshgarmon116 Wed, 02/19/2014 - 18:15
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jon, on that blog site you just gave me...how come the delay of R7's LOOPBACK O was NOT used in the formula for calculating the Feasible Distance from R8 to that Loopback?



nothing about 5,000...or 500 since it's divided by 10...was used in the (10,000,000/BW) + delay x 256 formula



let me know if you don't understand my question

Jon Marshall Thu, 02/20/2014 - 04:39
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Joshua


My sincere apologies. I gave that link as i did a quick read but on reading it again i don't think it works out.


It says it is calculating the metric to the loopback on R7. And then calcuates it to be 2169856. But looking at the EIGRP topology table on R8 the actual metric is 2297586. This because when it says you don't need to include the delay for the loopback interface you actually do so the delay value should be -


20000 + 5000 = 25000 / 10 = 2500


so the calculaton should be -


10,000,000 / 1544 = 6476.68 == 6476 EIGRP Metric = 256*(6476 + 2500) = 2297586


which matches what R8's topology table is reporting.


I have left a note on the site although the blog is quite old so i may not get a response and i may have misunderstood what the author was trying to say but from the above i would say you do indeed need to include the extra delay.


Does this help ?


Jon

joshgarmon116 Thu, 02/20/2014 - 10:52
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yes jon that does help



i wish that blog also included what subnet mask was used for the loopback addresses plus how EIGRP was configured but it didn't

Jon Marshall Thu, 02/20/2014 - 11:22
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Joshua


The subnet mask would be 255.255.255.255 which you can see by looking at EIGRP topology table ie. 7.7.7.7/32


In terms of the config it would be very simple ie. just two network statements on each router, one for the loopback and one for the network connecting the routers.


Plus a "no auto-summary" statement if it wasn't on by default.


Jon

joshgarmon116 Thu, 02/20/2014 - 11:54
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I actually tried that in GNS3 but for some reason, EIGRP was still not working.



I'm having trouble knowing what the networks and wildcard masks for the loopbacks are.

Jon Marshall Thu, 02/20/2014 - 12:09
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Looking at the topology table in that blog the loopbacks are not using /24 subnet masks they are using /32s.


So no they are not in the 7.7.7.0/24 and 8.8.8.0/24 networks they are 7.7.7.7/32 and 8.8.8.8/32


I have never not used "no auto-summary" in the production networks i have worked on. There may be a case not to use it if you actually did want a summary of the network but often in networks you want to summarise within a class and not to the classful mask.


You need to add it to both routers as each router summarises or doesn't regardless of what other routers are doing.



Jon

joshgarmon116 Thu, 02/20/2014 - 12:15
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alright so what should the wildcard masks be for the loopbacks.



i've never configured a broadcast address before.

Jon Marshall Thu, 02/20/2014 - 12:18
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Joshua


Sorry i just answered the specific question. From the blog -


R8(config-line)#int lo88

R8(config-if)#ip add 88.88.88.88 255.255.255.255

R8(config-if)#router eigrp 78

R8(config-router)#network 88.0.0.0


Jon

Jon Marshall Thu, 02/20/2014 - 12:36
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Can you post your current EIGRP configs on each router ?


Also, what does "sh ip eigrp neighbors" show ?


Jon

joshgarmon116 Thu, 02/20/2014 - 12:45
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jon, after configuring everything, i do a SH IP ROUTE.      




My configs for the loopbacks:



R7#config t

R7(config)#interface loopback 77

               #ip address 77.77.77.77 255.255.255.255

               #exit

               #router eigrp 78

               # network 77.0.0.0



R8#config t

R8(config)#interface loopback 88

               #ip address 88.88.88.88 255.255.255.255

               #exit

               #router eigrp 78

               #network 88.0.0.0



I also included the Serial addresses as well as "no auto-summary" in all of that



All my interfaces are turned on too.

Jon Marshall Thu, 02/20/2014 - 12:48
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Okay so you have included the network connecting the routers together.


Could you not have just posted the full EIGRP configuration ?


Anyway if you do a "sh ip eigrp neighbors" what do you see ?


Jon

joshgarmon116 Thu, 02/20/2014 - 12:52
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nothing in SH IP EIGRP TOPOLOGY either.



my actual eigrp configurations were this:



R7 conf t

     router eigrp 78

     network 77.0.0.0

     network 78.78.78.0

     no auto-summary



R8 conf t

     router eigrp 78

     network 88.0.0.0

     network 78.78.78.0

     no auto-summary

Jon Marshall Thu, 02/20/2014 - 12:54
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What does "sh ip eigrp neighbors" show ?


Jon

Jon Marshall Thu, 02/20/2014 - 12:57
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Can you ping the routers from each other ?


If so it sounds like a problem with GNS3 as there is nothing wrong with your configs.


What IOS version and feature set are you using ?


Jon

joshgarmon116 Thu, 02/20/2014 - 13:02
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Nope, can't ping anything other than the serial links...nothing for the loopback in my Routing Tables.



I'm thinking it's a GNS3 error too. There seems to be alot of limitations to this program. Half of the hyper visors (images) don't even work.



I did a SH VERSION and it says the IOS SOFTWARE is 7200 and the VERSION is 12.2 (33) SRC1, whatever that means.



Don't worry about it any longer...I just wanted to try it.

Jon Marshall Thu, 02/20/2014 - 13:09
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Joshua


Okay, does seem to be GNS3.


Not sure why it isn't working. I have used it before and it was pretty reliable.


Are you sure it isn't a memory/CPU issue ?


Did you do the memory value thing when you first started an IOS ?


Jon

joshgarmon116 Thu, 02/20/2014 - 13:26
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what's the memory value thing? i don't know what that is



i passed my ICDN1 and ICDN2 but i still don't know that much about Cisco Routing and Switching



i'm studying EIGRP right now and just wanted to try that topology on that blog site but it's just wasting my time right now so don't worry about it



thanks

Jon Marshall Thu, 02/20/2014 - 13:36
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what's the memory value thing? i don't know what that is

I haven't used GNS3 for a while but when you first start with an IOS the CPU goes up to almost 100% and stays there.


What you then need to do is find an idle value and enter this into your GNS3 config. This dramatically reduces the cpu usage used per IOS image and allows you to run multiple routers.


If it is still the same ie. you need to set this value and you haven't then i suspect most of the issues you are seeing is down to that providing you have enough memory as each IOS needs a certain amount of memory.  Like i say GNS is pretty reliable so it does suggest that may be the issue. If the CPU is running at almost full capacity it is not surprising things are not working.


The easy way to check is start up GNS3 and see what the CPU is doing.


i'm studying EIGRP right now and just wanted to try that topology on that blog site but it's just wasting my time right now so don't worry about it


I understand your frustration but it really is worth doing these things as you learn so much more.


There are a few people on these forums who use GNS3 and like i say i have in the past so it may be something relatively simple to get going.


It may not be that but it would be worth looking into it.


Jon

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