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

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

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

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

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.

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

alright so what should the wildcard masks be for the loopbacks.

i've never configured a broadcast address before.

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

EIGRP still NOT working.

i don't know

Can you post your current EIGRP configs on each router ?

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

Jon

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.

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