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Route Aggregation and supernetting
Trying to figure out the differences between route aggregation and supernetting.
Say the network 172.16.10.0/24 is running out of space. So I change the mask to /23
172.16.10.0/23=510 hosts
The "changing" of the subnet mask to a smaller one, is called route aggregation..right?
--------------------------
Now..................
172.16.10.0 with a 255.224.0.0 mask would be supernetting right? Since we are using *less* than the default class B mask?
Hope this makes sense.
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my cisco book defined it in an example, the example was something like:
" Let's say we have 172.16.10.0/24 and we need more host addresses. Currently /24 is only giving us 254. So we change the subnet mask to something smaller. 255.255.254.0 172.16.10.0/23. This gives us 510 hosts. This is called route aggregation. If we were to decrease the prefix of the default subnet mask, then this would be called supernetting."
That's where I got the idea from (sybex book by the way). Any ideas?
" Let's say we have 172.16.10.0/24 and we need more host addresses. Currently /24 is only giving us 254. So we change the subnet mask to something smaller. 255.255.254.0 172.16.10.0/23. This gives us 510 hosts. This is called route aggregation. If we were to decrease the prefix of the default subnet mask, then this would be called supernetting."
That's where I got the idea from (sybex book by the way). Any ideas?
OK, what Sybex is saying is this:
when they change the subnet mask from /24 to /23, the address range changes from
172.16.10.0 - 172.16.10.255
to
172.16.10.0 - 172.16.11.255
It is poorly worded but maybe they want supernetting to mean changing from
172.16.10.0
to
172.16.0.0
You other guys, any other ideas about this?
CajunBill
when they change the subnet mask from /24 to /23, the address range changes from
172.16.10.0 - 172.16.10.255
to
172.16.10.0 - 172.16.11.255
It is poorly worded but maybe they want supernetting to mean changing from
172.16.10.0
to
172.16.0.0
You other guys, any other ideas about this?
CajunBill
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I see, so aggregation is simply route summarization to the classful boundy. You will always advertise the IP address with it's default subnet mask?????????
supernetting breaks this rule ?
supernetting breaks this rule ?
Aggregation does not mean to the classful boundary, but to the smallest prefix possible.
harbor235
harbor235
Hold on there !
While harbor gave a good reference, it is quite old.
In current pratice it seems to me that these terms are used a little differently.
Real network professionals that I know do NOT think of supernetting and CIDR as the same thing.
In any case, you really shouldn't worry so much about the differences between these terms - you have the basic idea straight behind all of them.
If you are studying to take a test such as for CCNA - don't worry about it, you've got the idea well enough.
CajunBill
While harbor gave a good reference, it is quite old.
In current pratice it seems to me that these terms are used a little differently.
Real network professionals that I know do NOT think of supernetting and CIDR as the same thing.
In any case, you really shouldn't worry so much about the differences between these terms - you have the basic idea straight behind all of them.
If you are studying to take a test such as for CCNA - don't worry about it, you've got the idea well enough.
CajunBill
>Real network professionals that I know do NOT think of supernetting and CIDR as the same thing.
You cannot have supernetting without CIDR.
Here is another reference:
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci854054,00.html
http://www.networkdictionary.com/networking/cidr.php
http://business.cisco.com/glossary/tree.taf-asset_id=92888&word=99303&public_view=true&kbns=2&DefMode=.htm
A CIDR block or a SUPERNET, they are the same thing,
harbor235
You cannot have supernetting without CIDR.
Here is another reference:
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci854054,00.html
http://www.networkdictionary.com/networking/cidr.php
http://business.cisco.com/glossary/tree.taf-asset_id=92888&word=99303&public_view=true&kbns=2&DefMode=.htm
A CIDR block or a SUPERNET, they are the same thing,
harbor235
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hmmm so are route summarization and route aggregation the same thing? Except route summarization generally means summarizing to a classful boundary. Where Route aggregation (aka supernetting?) does NOT have to be classful???
Sounds good! :}
harbor235
harbor235
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thanks guys
ASKER
Let me just add the clarification that supernetting has nothing to do with the "default" class masks.
In general, those default masks are not really used any more in the Internet.
For quite a few years now what has been used is CIDR (Classless Routing).
The only place that classes show up these days is in older, less capable routing protocols like RIP.
HTH
Bill