Solutions to Scenario 114 Part APlanning

Keeping the design as simple as possible—yet not too simple, so that it is still useful as the network evolves—is a good practice. In the suggested answers in Tables 11-3 and 11-4, a numbering scheme is presented. Remember, this is one of many solutions available. The reasoning behind this planning is to allow summarization at the Area Border Routers. The first few bits in the third octet indicate the summarization bits. Note that these bits reflect the area; 1 bit or 128 identifies area 1, while 3 bits or 224 identify area 3.

Table 11-3 Scenario 11-4, Part A—IP Subnet Network Planning Chart Solution

Geographic Location of Subnet/Network

Bit Pattern of Subnet Number Last Two Octets

Prefix Subnet Mask

Ethernet 0 Ethernet 1 Ethernet 2

131.99.0.48

131.99.136.128

131.99.144.128

00000000 0011 0000 /28 10001000 1000 0000 /28 10010000 1000 0000 /28

255.255.255.240 255.255.255.240 255.255.255.240

continues

Table 11-3 Scenario 11-4, Part A—IP Subnet Network Planning Chart Solution (Continued)

Geographic Location of Subnet/Network

Subnet Number

Bit Pattern of Last Two Octets

Prefix

Subnet Mask

Ethernet 0

131.99.0.48

00000000 0011 0000

/28

255.255.255.240

Ethernet 1

131.99.192.192

11000000 1100 0000

/28

255.255.255.240

Ethernet 2

131.99.216.192

11011000 1100 0000

/28

255.255.255.240

Ethernet 0

131.99.0.48

00000000 0011 0000

/28

255.255.255.240

Ethernet 1

131.99.224.224

11100000 1110 0000

/28

255.255.255.240

Ethernet 2

131.99.232.224

11101000 1110 0000

/28

255.255.255.240

Serial between

A1 and A2

131.99.128.128

10000000 1000 0000

/26

255.255.255.192

A1

Ethernet 0

131.99.136.128

10001000 1000 0000

/28

255.255.255.240

Ethernet 1

VLANs

Floor 1

131.99.136.0

10001000 0 0000000

/25

255.255.255.128

Floor 2

131.99.137.0

10001001 0 0000000

/25

255.255.255.128

Floor 3

131.99.138.0

10001010 0 0000000

/25

255.255.255.128

Floor 4

131.99.139.0

1000101100000000

/25

255.255.255.128

Floor 5

131.99.140.0

1000110000000000

/25

255.255.255.128

Floor 6

131.99.141.0

1000110100000000

/25

255.255.255.128

Floor 7

131.99.142.0

1000111000000000

/25

255.255.255.128

A2

Ethernet 0

131.99.144.128

10010000 1000 0000

/28

255.255.255.240

Ethernet 1

VLANs

Floor 1

131.99.144.0

10010000 0 0000000

/25

255.255.255.128

Floor 2

131.99.145.0

10010001 0 0000000

/25

255.255.255.128

Floor 3

131.99.146.0

10010010 0 0000000

/25

255.255.255.128

Floor 4

131.99.147.0

1001001100000000

/25

255.255.255.128

Floor 5

131.99.148.0

10010100 0 0000000

/25

255.255.255.128

Floor 6

131.99.149.0

10010101 0 0000000

/25

255.255.255.128

Floor 7

131.99.150.0

1001011000000000

/25

255.255.255.128

Table 11-3 Scenario 11-4, Part A—IP Subnet Network Planning Chart Solution (Continued)

Geographic Location of Subnet/Network

Subnet Number

Bit Pattern of Last Two Octets

Prefix

Subnet Mask

Serial between B1 and B2

131.99.192.128

11000000 10 000000

/26

255.255.255.192

B1

Ethernet 0

131.99.192.192

11000000 1100 0000

/28

225.255.255.240

Ethernet 1

VLANs

Floor 1

131.99.200.0

11001000 0 0000000

/25

255.255.255.128

Floor 2

131.99.201.0

11001001 0 0000000

/25

255.255.255.128

Floor 3

131.99.202.0

11001010 0 0000000

/25

255.255.255.128

Floor 4

131.99.203.0

1100101100000000

/25

255.255.255.128

Floor 5

131.99.204.0

1100110000000000

/25

255.255.255.128

Floor 6

131.99.205.0

1100110100000000

/25

255.255.255.128

Floor 7

131.99.206.0

1100111000000000

/25

255.255.255.128

B2

Ethernet 0

131.99.216.192

11011000 1100 0000

/28

225.255.255.240

Ethernet 1

VLANs

Floor 1

131.99.216.0

1101100000000000

/25

255.255.255.128

Floor 2

131.99.217.0

1101100100000000

/25

255.255.255.128

Floor 3

131.99.218.0

1101101000000000

/25

255.255.255.128

Floor 4

131.99.219.0

1101101100000000

/25

255.255.255.128

Floor 5

131.99.220.0

1101110000000000

/25

255.255.255.128

Floor 6

131.99.221.0

1101110100000000

/25

255.255.255.128

Floor 7

131.99.222.0

1101111000000000

/25

255.255.255.128

Serial between C1 and C2

131.99.224.128

11100000 10 000000

/26

255.255.255.192

continues continues

Table 11-3 Scenario 11-4, Part A—IP Subnet Network Planning Chart Solution (Continued)

Geographic Location

Bit Pattern of

of Subnet/Network

Subnet Number

Last Two Octets

Prefix

Subnet Mask

C1

Ethernet 0

131.99.224.224

11100000 1110 0000

/28

225.255.255.240

Ethernet 1

VLANs

Floor 1

131.99.224.0

11100000 0 0000000

/25

255.255.255.128

Floor 2

131.99.225.0

1110000100000000

/25

255.255.255.128

Floor 3

131.99.226.0

1110001000000000

/25

255.255.255.128

Floor 4

131.99.227.0

1110001100000000

/25

255.255.255.128

Floor 5

131.99.228.0

1110010000000000

/25

255.255.255.128

Floor 6

131.99.229.0

1110010100000000

/25

255.255.255.128

Floor 7

131.99.230.0

1110011000000000

/25

255.255.255.128

C2

Ethernet 0

131.99.232.224

11101000 1110 0000

/28

255.255.255.240

Ethernet 1

VLANs

Floor 1

131.99.232.0

1110100000000000

/25

255.255.255.128

Floor 2

131.99.233.0

1110100100000000

/25

255.255.255.128

Floor 3

131.99.234.0

1110101000000000

/25

255.255.255.128

Floor 4

131.99.235.0

1110101100000000

/25

255.255.255.128

Floor 5

131.99.236.0

1110110000000000

/25

255.255.255.128

Floor 6

131.99.237.0

1110110100000000

/25

255.255.255.128

Floor 7

131.99.238.0

1110111000000000

/25

255.255.255.128

Scenario 11-4, Part A—OSPF Area Planning Chart Solution

Table 11-4

Scenario 11-4, Part A—OSPF Area Planning Chart Solution

Router Location

OSPF Router Type

Reason

A in Area 0 and Area 1

Backbone router and Area Border Router (ABR). The interface into Area 1 is configured as a stub area.

The router has an interface in both Area 0 and Area 1; it is at the core of the network. The interface into Area 1 will not send external routes into the area, but it may generate default route and summary routes.

B in Area 0 and Area 2

Backbone router and Area Border Router (ABR). The interface into Area 1 is configured as a stub area.

The router has an interface in both Area 0 and Area 1; it is at the core of the network. The interface into Area 2 will not send external routes into the area, but it may generate default route and summary routes.

Table 11-4 Scenario 11-4, Part A—OSPF Area Planning Chart Solution (Continued)

Router Location

OSPF Router Type

Reason

C in Area 0 Backbone router and Area and Area 3 Border Router (ABR). The interface into Area 1 is not configured as a stub area because the area has RIP redistributed into the area.

The router has an interface in both Area 0 and Area 1; it is at the core of the network. The interface into Area 3 will not send external routes into the area, but it will generate a default route. Because this area is the only area that has external routes, this is not an issue. However if the organization ever connects into the Internet, then additional configuration will be necessary to distinguish between the Internet and the RIP network.

A1 Internal router and stub It is in Area 1 only using summarization, with no need area router into Area 1. for the RIP networks; it can therefore be configured as a stub area.

A2

Internal router and stub area router into Area 1.

It is in Area 1 only using summarization with no need for the RIP networks; it can therefore be configured as a stub area.

B1

Internal router and stub area router into Area 2.

It is in Area 2 only using summarization with no need for the RIP networks; it can therefore be configured as a stub area.

B2

Internal router and stub area router into Area 2.

It is in Area 2 only using summarization with no need for the RIP networks; it can therefore be configured as a stub area.

C1

Internal router to Area 3.

This router cannot be a stub area router because the area has RIP redistributed into it.

C2

An Autonomous System Border Router (ASBR)

Because the building that this router serves has UNIX servers running RIP, and because these networks need to be accessible to the organization, RIP needs to be redistributed into the OSPF domain. Redistributed routes are considered as external routes—thus the configuration of an ASBR.

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