Download SEMESTER 1 Chapter 5

SEMESTER 2 Chapter 6
VLSM and CIDR
V 4.0
6.1.1
6.1.1.2
6.1.1.3
6.1.2
6.1.3
6.1.3.2
6.1.4
Why were VLSM, CIDR, NAT,
and private addressing
developed?
What is the range for Class A
addresses?
What is the range for Class B
addresses?
What is the range for Class C
addresses?
What are ip addresses that
begin with 4 1 bits reserved
for?
How many hosts are available
for Class C addresses?
How can you determine the
subnet mask for a classful ip
address?
How many host addresses are
available for Class B
addresses?
What two things did Classless
Inter-Domain Routing (CIDR)
allow for?
What does the address class
mean to CIDR?
What process does CIDR
allocate IP addresses
according to subnets rather
than by class?
What does prefix aggregation
do to the routing tables?
What is another name for a
route that has been aggregated
be called?
What must be included in the
routing update when you use
classless routing?
What are the 5 classless
routing protocols?
When are classless routing
protocols necessary?
Do you have to use route
summarization in a classless
routing environment?
We would have run out of ip addresses
0.0.0.0-127.255.255.255
128.0.0.0-191.255.255.255
192.0.0.0-223.255.255.255
Future use
254
The first octet
65,534
More efficient use of IPv4 address space
Prefix aggregation, which reduced the size of routing
tables
Nothing
Variable Length Subnet Masks (VLSM)
Decreases the size
Supernet route
The subnet mask
RIPv2, EIGRP, OSPF, IS-IS, and BGP
when the mask cannot be assumed or determined by
the value of the first octet
No
6.2.1
6.2.2
6.3.1
6.3.2
What is another name for
VLSM?
If you start with /16 subnet, how
many subnets are available?
If sub-subnet a /16 subnet, to
/28 how many subnets are
created for each of the original
subnets?
What is the process of
advertising a contiguous set of
addresses as a single address
with a less-specific, shorter
subnet mask called?
Explain the difference between
route summarization in RIPv1
and supernetting?
When you summarize a set of
routes what is the first step?
What is matched in the second
step of route summarization?
What is the final step in route
summarization?
* What is VLSM? What is CIDR?
Subnetting a subnet
Sub-subnetting
28 = 256 subnets
212 = 4,096 per subnet
Route aggregation
Route summarization
Supernetting
Supernetting ignores the limitation of classful
boundaries, whereas RIPv1 summarizes to the single
major network classful address
List all the networks in binary
Match the left-most bits to get the summary address
Copy all the matching bits and place zeros after them
to determine the summarized network address
* What is the advantage of CIDR (classless routing protocols) over the original classful
routing protocol?
* What is supernet?
* /25
/26
/27
/28
/29
/30
= 255.255.255.128 = 128 addresses = 126 usable addresses
= 255.255.255.192 = 64 addresses = 62 usable addresses
= 255.255.255.224 = 32 addresses = 30 usable addresses
= 255.255.255.240 = 16 addresses = 14 usable addresses
= 255.255.255.248 = 8 addresses = 6 usable addresses
= 255.255.255.252 = 4 addresses = 2 usable addresses
(You will use this table for several questions)
In addition to know the block size, and its relation to subnet, you also need to know the
1st address of each block is the network address, last address is the broadcast address,
and anything in between are the usable addresses.
* Here is a quick table for using subnet mask to figure out the following:
- Which one is the network address?
- Which one is the broadcast address?
- Which are the usable addresses?
(You will use this table for several questions)
255.255.255.128 (or /25)
0 - 127
128 - 255
255.255.255.192 (or /26)
0 - 63
64 - 127
128 - 191
192 - 255
* 255.255.255.224 (or /27)
0 - 31
32 - 63
64 - 95
96 - 127
128 - 159
160 - 191
192 - 223
224 - 255
Same process for 255.255.255.240 (/28) and 255.255.255.248 (/29)
* If the network is using RIPv1, what network entry and mask would router R1 send to
R2? What network entry and mask would router B send to A and C? What network
entry and mask would router C send to B?
[Hint: 1. You need to understand the process of network update when network
are all contiguously connected.
2. When networks are not contiguously connected, you need to understand the
process of network auto-summarization on network boundary. ]
* What is the summarized address for the following network addresses?
•
•
•
•
•
•
•
•
192.168.0.0/30
192.168.0.4/30
192.168.0.8/30
192.168.0.16/29
192.168.4.0/30
192.168.5.0/30
192.168.6.0/30
192.168.7.0/29
* Continue from the question above, can you do it the other way around? If I give you a
summarized address with 192.168.64.0 /20, can you figure out what networks are
included in this summarized address?
* You have a class C network and VLSM is not used and the networks are all /26. How
many address actually get used and how many are wasted for the 3 point-to-point
connections between these 3 routers?
- Make sure you understand the definition of the term “point-to-point”. It means
the link will only provide the inter-connection between 2 routers and will only
need 2 valid IP address.
- The most efficient subnet mask for the point-to-point is /30.
* You have 4 networks and they have network addresses and subnet mask listed below:
Network 1 only has 5 hosts on 10.1.1.0 /29.
Network 2 only has 13 hosts on 10.1.1.32 /28
Network 3 only has 30 hosts on 10.1.1.64 /26
Network 4 only has 124 hosts on 10.1.1.128 /25
How many total address have you actually assigned and used by the hosts and how
many IP address are not assigned and wasted?
* This is probably the most time consuming and most difficult question for this chapter.
The segment area marked with the question mark will have maximum of 14 hosts.
What is its network address for this segment?
[Hint: step 1: figure out what addresses has not been used yet.
step 2: from the left over, then you need to figure out which one will take 14 hosts]
* Can you have the network with the following configuration? Why? Why not?
10.0.1.128 /25
10.0.1.192 /26
* R1 ca not ping host B, and all the testing below shows ping are successful. What is
most likely the problem?
1. pings from R1 to the S0/0/0 interface on R2....successful
2. pings from R1 to the Fa0/0 interface on R2....successful
3. pings from host B to hosts on the 10.1.1.0/24 network....successful
4. pings from host B to the Fa0/0 interface on R2....successful
5. pings from R2 to host B....successful.
Hint:
1) Router can reach the other router.  Routers are good & Routes are good.
2) Router can reach all the interface for other router.  Routers are good.
3) B can reach the IP address on the router2.  B NIC is good Router is good.
4) B can reach the other hosts in the same subnet.  B is good.
5) R2 can reach the B.  R2 is good and B is good.
Use the process of elimination; you should be able to figure out the answer when you
see the question.