Can you expain summarization?
Raymond Mason
Member Posts: 74 ■■□□□□□□□□
in CCNA & CCENT
Hello! I have Todd Lammles book for study material. I understand how to subnet and I understand VSLM. What I am having trouble with is summarization.
I understand that its used to just to summarize a bunch of networks to ease router memory. I get the gist of what its meant to do; but the book words it in a way where I don't understand how its done.
For example:
192.168.16.0 through network 192.168.31.0
He says there is exactly 16 class 16 Class C networks. I don't quiet get where he got 16 networks from; he doesn't give a notation or subnet mask. Maybe you guys can word this different? Thanks again!
I understand that its used to just to summarize a bunch of networks to ease router memory. I get the gist of what its meant to do; but the book words it in a way where I don't understand how its done.
For example:
192.168.16.0 through network 192.168.31.0
He says there is exactly 16 class 16 Class C networks. I don't quiet get where he got 16 networks from; he doesn't give a notation or subnet mask. Maybe you guys can word this different? Thanks again!
Comments
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PCTechLinc
Member Posts: 646 ■■■■■■□□□□
192.168.16.0 and 192.168.31.0 both have a default subnet mask of 255.255.255.0. That means that past the last octect (.0), every number change is a different network. So, 16.0 - 31.0 are 16 separate networks.
If you change the subnet mask to 255.255.240.0, then that will summarize all those 16 networks into one block, and when you look at the router graphically, you'll see that the router knows how to forward ANY address from ANY of those networks out of one interface. Hence, why summarization "compresses" the routing table so efficiently.
Hope that makes sense!Master of Business Administration in Information Technology Management - Western Governors University
Master of Science in Information Security and Assurance - Western Governors University
Bachelor of Science in Network Administration - Western Governors University
Associate of Applied Science x4 - Heald College -
nice343
Member Posts: 391
I hope the attached table gives you some clarification
It shows the number of /24 each subnet mask will have.
The range for a /20 is x.y.0.1 - x.y.15.254 (16 /24 subnets including the 0)
Based on your example
192.168.16.0 through network 192.168.31.0
If we look at the 3rd octet
16 + 15 = 31
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pinkiaiii
Member Posts: 216
I ran into simillar issue but with wildcard masks included in ospf or eigrp-since seems for some networks when you summarize you can use like ip 192.168.4.1 0.0.0.255,in other cases you need to use specifically 192.168.4.0 0.0.0.255 or am i crossing between the two in the wrong way where if using full address and wildcard mask is just for single ip, where if using 192.168.4.0 0.0.0.255 for summarized route ?
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james43026
Member Posts: 303 ■■□□□□□□□□
I'm going to take a different approach to answering this. Route summarization / aggregation is also called supernetting. I'll assume you understand subnetting, and the fact that under all circumstances, when you subnet, you are borrowing host bits, in order to increase the number of network bits. Supernetting is the opposite, you are borrowing network bits in order to increase the number of host bits, this essentially takes several smaller networks, and aggregates them into one larger network. Let me know if you need an example.