contiguous , discontiguous network question

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as an example i ask this :

"A contiguous network is a single Class A, B, or C network for which all routes to subnets of that network pass through only other subnets of that same single network"

"Discontiguous networks refer to the concept that, in a single Class A, B, or C network, there is at least one case in which the only routes to one subnet pass through subnets of a different network."

due to above

8.0.0.0/16 , 9.0.0.0.0/16 , 10.0.0.0/16 , 11.0.0.0/16

are these contiguous?

i asked because they are all class A but they are different
networks (network.host.host.host) and

different networks mean one is class A ,one is class C ...?
or for ex.

10.0.0.0/16 , 10.1.0.0/16 , 10.2.0.0/16 these are same subnets
of a single same network and all class A.


one more question: classful network is only for ex. for class A /8 , class B/16 , for class C /24?
i want to learn this because eigrp summarizes at classful network boundaries but i saw an example
and in it there was 172.16.10.0/24 so where is the classful network?

 

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Using the above definitions (remember - I'm not a Cisco cert holder) the answer is No.

That is the reason I said 'no'. Note that you haven't actualy shown any routing, so there are cases where the answer might be 'maybe - not enough info'.

The class is irrelevant - they are all Class As but different networks.

For those the answer is a 'maybe' as you haven't shown any routing. Note that for some definitions of subnetting the first address shown would not be valid. I don't know what Cisco says about it though.

Note that *my* view is that the minute somebody talks about Classes I assume old class rules rather than CIDR. I have seen cases where the two have been muddled up. Again - I don't know Cisco-speak, so I may have misinterpreted it.

Harry.

 

I give up, kobem, sorry. I've suggested that you learn subnetting, and you obviously haven't listened to my advice. You ask questions that would be easily answered by yourself if you understood subnetting.

I'll answer your first question: No.

8.0.0.0/16, 9.0.0.0/16, 10.0.0.0/16, and 11.0.0.0/16 are not contiguous address ranges.
8.0.0.0/8, 9.0.0.0/8, 10.0.0.0/8, and 11.0.0.0/8 ARE contiguous address ranges.

When you understand what that little slash-number means at the end of the address, then you'll understand why.

 

i know what / means man , it shows you how many bits are 1
so if it is /8 then subnet mask goes 255.0.0.0 why
because of 11111111 . 000000.... you saw that
8 bits are 1 ok?

but in my opinion if we use /16 with 8.0.0.0 , 9.0.0.0 , 10.0.0.0
we owe 8 bits from hosts 16 - 8 = 8

so if we owe 8 bits for each they will be same again. what
will change?

 

Yes, it shows how many bits are 1s in the subnet mask... but what does the subnet mask mean? You have to know what the subnet mask is used for. And from your post above, you either don't know what it's used for, or you're not explaining yourself well.

I have no idea what you mean by "we owe 8 bits from hosts 16 - 8 = 8" when discussing /16. /16 means 16 bits of the address are used for the network portion of the address. Thus, the address 8.0.0.0/16 means that 8.0. is the network portion of the address.

When asking if 8.0.0.0/16 and 9.0.0.0/16 are contiguous, the answer is no, because you have the 8.0. and 9.0. network. That means you've only got the addressses from 8.0.0.0 to 8.0.255.255, and 9.0.0.0 to 9.0.255.255. In between the 8.0.0.0/16 and 9.0.0.0/16 networks, you've got the 8.1. network, the 8.2. network, the 8.3. network, and so on. Thus, these two ranges cannot be summarized.

The address 8.0.0.0/8 means that 8. is the network portion of the address. When asking if 8.0.0.0/8 and 9.0.0.0/8 are contiguous, the answer is yes, because you have the 8. and 9. network. Nothing is between them - you've got ALL the addresses from 8.0.0.0 to 9.255.255.255. Thus, these two ranges can be summarized.

 

but if you say 8 and 9 are the networks , you explain yourself
they are different networks. 8 and 9 networks .

i am sorry but why can't we summarize if slash is 16 ?

note : i have sybex and finished it in time but i ask these
because either sybex and other materials don't tell me
the answers and i can't find the answer.




for example sybex says "eigrp summarizes at classful network boundaries" and it used 172.16.1.0/24 network so are you crazy
eigrp where is the classfullness? (eigrp is not classful also)

another one : i read everywhere i could . route summarization ,route aggregation ,supernetting , cidr ,auto summarization , manual
summarization but all of them look same i can't distinguish them. Am i stupid?
and i am Turkish , my english is very good but not as good as an english or native American person so that
i can't understand some things.

you want more?

what is classful network is this just /8 for class A , /16 for class B , /24 for class C?

wan cabling ? (we use ethernet standards for lans , like utp ,stp or coaxial or fibre then if we try to communicate
two routers
1- if they are in same building?
2- they are in each branch office of a company? (i mean one of them is in chicago one of them is in denver for ex)

3- if we want to use dte and dce cable in which condition it will be necessary?(i asked since
if routers are in a position like 2 (above) it won't be possible?

4 - can i use fibre between two routers ?


PLEASE REPLY FOR THESE TO ME , I CAN'T GET ANSWER FROM OTHER FORUMS OR SOURCES PLEASE

 

I see that we are getting into rather more complex Cisco stuff and I'm not sure that I can help very much here. However, I note that there seems to be confusion between "contiguous networks" and "contiguous addresses" - these are not the same thing as far as I understand things. I answered the question from the point of contiguous networks, not contiguous addresses.

Er - You have already asked this and I answered. What was wrong with the answers?

Harry.

 

I told you - because you don't control the subnets between 8.0.0.0/16 and 9.0.0.0/16. Meaning, you don't control:
8.1.0.0/16
8.2.0.0/16
8.3.0.0/16
8.4.0.0/16
...etc.

You have to have administrative control over these subnets to summarize 8.0.0.0 and 9.0.0.0 together. Otherwise, you will incorrectly route packets destined for 8.1.0.0/16, 8.2.0.0/16, etc.

If I remember correctly, EIGRP automatically summarizes at classful boundaries, but that can be disabled.

If you don't understand those terms, you need to learn them. I honestly don't have the time to explain each one to you in detail. Entire books have been written on this subject. A single post would probably not help the matter.

Any other brave souls who are willing to take on this challenge, be my guest.

Yes. If you use classless, then there IS no Class A, Class B, Class C. All you have are subnet masks.

Harry already answered these questions.

 

sorry but

brainbeaconmichael

I told you - because you don't control the subnets between 8.0.0.0/16 and 9.0.0.0/16. Meaning, you don't control:
8.1.0.0/16
8.2.0.0/16
8.3.0.0/16
8.4.0.0/16
...etc.

You have to have administrative control over these subnets to summarize 8.0.0.0 and 9.0.0.0 together. Otherwise, you will incorrectly route packets destined for 8.1.0.0/16, 8.2.0.0/16, etc.

...................................
kobem again

still don't understand what you mean here , for ex. sybex used 172.16.10.0/24 so?
..................................
brainbeaconmichael

If I remember correctly, EIGRP automatically summarizes at classful boundaries, but that can be disabled.

...................................
kobem again


auto summary in eigrp at classful boundary ? 172.16.10.0/24 , 10.3.1.0/24 ,172.16.20.0/24
and by default network both goes 172.16.0.0 and for 10 it goes 10.0.0.0
yes is this the classful boundary summarization ?

....................................

kobem

wan cabling ? (we use ethernet standards for lans , like utp ,stp or coaxial or fibre then if we try to communicate
two routers
1- if they are in same building?
2- they are in each branch office of a company? (i mean one of them is in chicago one of them is in denver for ex)

3- if we want to use dte and dce cable in which condition it will be necessary?(i asked since
if routers are in a position like 2 (above) it won't be possible?

4 - can i use fibre between two routers ?

..................................
kobem again

please reply these with your own words
.................................

 

If you don't understand what I mean, then you really don't understand subnetting, and I've been trying to tell you that. I'd suggest reading through this site. Or, you can ignore me and keep on asking questions. But you still need to understand subnetting.

Yes, EIGRP will auto-summarize at the classful boundary. 172.16.10.0/24 and 172.16.10.0/24 will be summarized to 172.16.0.0/16, but if you've got any other 172.16.x.0/24 networks using a different route, you've got a discontiguous network situation. 10.3.1.0/24 auto-summarizes to 10.0.0.0/8.

1. You can connect routers by whatever interfaces you have. I personally don't have multiple routers in the same location because I have a single router at each location that connects to my WAN circuits. If I did have multiple routers at a location, I might use an ethernet interface with UTP cable. It's up to you.

2. Depends on how you connect those remote locations. I use UTP to connect our locations to T1s and Metro Ethernet. Also used to use Frame Relay.

3. No idea. I honestly haven't used DTE/DCE cables in years.

4. If the router has a fibre interface, sure.

 

I'm new to the threads but thought the book, Top-down network design 3rd Edition might help you for your Cisco stuff. Specifically the third chapter which covers the questions which you're asking.

 

I think he'll have figured it out by now, it shouldn't take 5 years ;).

 

I'm not so sure about that.