Lab 2.10.2a VLSM 1
Objective
Create an addressing scheme using variable length subnet masking (VLSM).
Scenario
The assignment is the Class C address 192.168.10.0 and it must support the network shown in the
diagram. The use of IP unnumbered or NAT is not permitted on this network. Create an addressing
scheme that meets the requirements shown in the diagram.
Sample Solution: (using subnet zero)
1. 192.168.10.0/24 yields 64 (2^6=64) subnets (192.168.10.0 through 192.168.10.255) with two
host addresses per subnet - recall that the default setting of ip subnet-zero allows the all 0s
and the all 1s networks. Note that 12.2T IOS releases allow for 31 bit prefixes on point-to-point
links. According to CCO, the use of 31-bit subnet masks within the core of the Internet reduces
the number of physical links against which a denial of service (DoS) attack can be launched. We
restrict our design to 30-bit masks for point-to-point links
2. Serial links can be assigned the following:
a. 192.168.10.4/30 with host addresses 192.168.10.5 and 192.168.10.6
b. 192.168.10.8/30 with host addresses 192.168.10.9 and 192.168.10.10
c. 192.168.10.12/30 with host addresses 192.168.10.13 and 192.168.10.14
3. LANs could be assigned the following subnets with respective masks to accommodate the
number of hosts required on each subnet.
a. LAN 1 - 12 hosts: 192.168.10.32/28
b. LAN 2 - 12 hosts: 192.168.10.48/28
c.
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LAN 3 - 28 hosts: 192.168.10.64/27
CCNP 1: Advanced Routing v 3.0 - Lab 2.10.2a
(24=16, 16-2=14 hosts from 192.168.10.33
to 192.168.10.46)
(24=16, 16-2=14 hosts from 192.168.10.49
to 192.168.10.62)
(25=32, 32-2=30 hosts from 192.168.10.65
Copyright  2003, Cisco Systems, Inc.
d. LAN 4 - 60 hosts: 192.168.10.96/26
to 192.168.10.94)
(26=64, 64-2=62 hosts from 192.168.10.97
to 192.168.10.158)
This leaves the address range of 192.168.10.160 to 192.168.10.255.
Note: LAN addressing did not start at 192.168.10.16 to leave room for expansion of serial
links.
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CCNP 1: Advanced Routing v 3.0 - Lab 2.10.2a
Copyright  2003, Cisco Systems, Inc.
Lab 2.10.2b VLSM 2
Objective
Create an addressing scheme using subnetting and/or variable length subnet masking (VLSM).
Scenario
The assignment is the Class C address 192.168.10.0 and it must support the network shown in the
diagram. The use of IP unnumbered, NAT, or /31 subnets (available on point-to-point networks with
IOS Release 12.2) are not permitted on this network. Create an addressing scheme that meets the
requirements shown in the diagram. First, attempt an IP addressing scheme using traditional
subnetting. If that proves to be impossible, use VLSM.
Sample Solution: (using subnet zero)
1. 192.168.10.0/24 yields 64 (26=64) subnets (192.168.10.0 through 192.168.10.255) with two host
addresses per subnet.
2. Serial links can be assigned the following:
a. 192.168.10.0/30 with host addresses 192.168.10.1 and 192.168.10.2
b. 192.168.10.4/30 with host addresses 192.168.10.5 and 192.168.10.6
c. 192.168.10.8/30 with host addresses 192.168.10.9 and 192.168.10.10
3. LANs could be assigned the following subnets with respective masks to accommodate the
number of hosts required on each subnet.
a. LAN 1 - 2 hosts: 192.168.10.12/30
b. LAN 2 - 10 hosts: 192.168.10.16/28
c.
LAN 3 - 30 hosts: 192.168.10.32/27
d. LAN 4 - 60 hosts: 192.168.10.64/26
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CCNP 1: Advanced Routing v 3.0 - Lab 2.10.2b
(22=4, 4-2=2 hosts from 192.168.10.13
to 192.168.10.14)
(24=16, 16-2=14 hosts from 192.168.10.15
to 192.168.10.30)
(25=32-2=30 hosts from 192.168.10.33
to 192.168.10.62)
(26=64-2=62 hosts from 192.168.10.65
to 192.168.10.126)
Copyright  2003, Cisco Systems, Inc.
e. LAN 5 - 120 hosts: 192.168.10.128/25
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CCNP 1: Advanced Routing v 3.0 - Lab 2.10.2b
(27=128, 128-2=126 hosts from
192.168.10.129 to 192.168.10.254)
Copyright  2003, Cisco Systems, Inc.
Lab 2.10.2c VLSM 3
Objective
Create an addressing scheme using VLSM.
Scenario
The assignment is the CIDR address 192.168.24.0/22, and it must support the network shown in the
diagram. The use of IP unnumbered or NAT is not permitted on this network. Create an addressing
scheme that meets the requirements shown in the diagram.
Sample Solution: (using subnet zero)
1. 192.168.24.0/22 yields 64 (28=256) subnets (192.168.24.0 through 192.168.27.255) with two
host addresses per subnet.
2. Serial links can be assigned the following:
a. 192.168.24.0/30 with host addresses 192.168.24.1 and 192.168.24.2
b. 192.168.24.4/30 with host addresses 192.168.24.5 and 192.168.24.6
c. 192.168.24.8/30 with host addresses 192.168.24.9 and 192.168.24.10
3. LANs could be assigned the following subnets with respective masks to accommodate the
number of hosts required on each subnet.
a. LAN 1 - 50 hosts: 192.168.24.64/26
b. LAN 2 - 50 hosts: 192.168.24.128/26
(26=64, 64-2=62 hosts from 192.168.24.65
to 192.168.24.126)
(26=64, 64-2=62 hosts from
192.168.24.129 to 192.168.24.190)
c.
LAN 3 - 200 hosts: 192.168.25.0/24 (28=256, 256-2=254 hosts from 192.168.25.1 to
192.168.25.254)
d. LAN 4 - 400 hosts: 192.168.26.0/23 (29=512, 512-2=510 hosts from 192.168.26.1 to
192.168.27.254)
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CCNP 1: Advanced Routing v 3.0 - Lab 2.10.2d
Copyright  2003, Cisco Systems, Inc.
Lab 2.10.2d VLSM 4
Objective
Create an addressing scheme using VLSM.
Scenario
The assignment is the CIDR address 192.168.30.0/23, and it must support the network shown in the
diagram. The use of IP unnumbered or NAT is not permitted on this network. Create an addressing
scheme that meets the requirements shown in the diagram.
Sample Solution: (using subnet zero)
1. 192.168.30.0/23 yields 2 supernets (21=2) 192.168.30.0 and 192.168.31.0 and 512 total hosts
(29=512) 192.168.30.0 through 192.168.31.254.
2. Serial links can be assigned the following:
a. 192.168.31.192/30 with host addresses 192.168.31.193 and 192.168.31.194
b. 192.168.31.196/30 with host addresses 192.168.31.197 and 192.168.31.198
c. 192.168.31.200/30 with host addresses 192.168.31.201 and 192.168.31.202
Note: Addresses assigned to the serial interfaces were selected from the end of the
addresses assigned to the LANs in Step 3 below. This leaves the address range
192.168.31.204 through 192.168.31.255.
3. LANs could be assigned the following subnets with respective masks to accommodate the
number of hosts required on each subnet.
a. LAN 1- 120 hosts: 192.168.30.0/25
b. LAN 2 - 90 hosts: 192.168.30.128/25
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CCNP 1: Advanced Routing v 3.0 - Lab 2.10.2d
(27=128, 128-2=126 hosts from
192.168.30.1 to 192.168.30.126)
(27=128, 128-2=126 hosts from
192.168.30.129 to 192.168.30.254)
Copyright  2003, Cisco Systems, Inc.
c.
LAN 3 - 60 hosts: 192.168.31.0/26
d. LAN 4 - 24 hosts: 192.168.31.64/27
e. LAN 5 - 30 hosts: 192.168.31.96/27
f.
LAN 6 - 20 hosts: 192.168.31.128/27
g. LAN 7 - 24 hosts: 192.168.31.160/27
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CCNP 1: Advanced Routing v 3.0 - Lab 2.10.2d
(26=64, 64-2=62 hosts from 192.168.31.1
to 192.168.31.62)
(25=32, 32-2=30 hosts from 192.168.31.65
to 192.168.31.94)
(25=32, 32-2=30 hosts from 192.168.31.97
to 192.168.31.126)
(25=32, 32-2=30 hosts from 192.168.31.129
to 192.168.31.158)
(25=32, 32-2=30 hosts from 192.168.31.161
to 192.168.31.190)
Copyright  2003, Cisco Systems, Inc.