ZyXEL MAX207HW2 User Manual
Appendix D IP Addresses and Subnetting
Notation
Since the mask is always a continuous number of ones beginning from the left,
followed by a continuous number of zeros for the remainder of the 32 bit mask,
you can simply specify the number of ones instead of writing the value of each
octet. This is usually spec if i e d by wri t ing a “/” followed by the number of bits in
the mask after the address.
For example, 192.1.1.0 /25 is equivalent to saying 192.1.1.0 with subnet mask
255.255.255.128.
The following table shows some possible subnet masks using both notations.
Table 74 Alternative Subnet Mask Notation
SUBNET MASK
255.255.255.0 /24 0000 0000 0
255.255.255.128 /25 1000 0000 128
255.255.255.192 /26 1100 0000 192
255.255.255.224 /27 1110 0000 224
255.255.255.240 /28 1111 0000 240
255.255.255.248 /29 1111 1000 248
255.255.255.252 /30 1111 1100 252
ALTERNATIVE
NOTATION
LAST OCTET
(BINARY)
LAST OCTET
(DECIMAL)
Subnetting
You can use subnetting to divide one network into multiple sub-networks. In the
following example a network administrator creates two sub-networks to isolate a
group of servers from the rest of the company network for security reasons.
In this example, the company network address is 192.168.1.0. The first three
octets of the address (192.168.1) are the network number, and the remaining
octet is the host ID, allowing a maximum of 2
8
– 2 or 254 possible hosts.
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Appendix D IP Addresses and Subnetting
The following figure shows the company network before subnetting.
Figure 119 Subnetting Example: Before Subnetting
You can “borrow” one of the host ID bits to divide the network 192.168.1.0 into
two separate sub-networks. The subnet mask is now 25 bits (255.255.255.128 or
/25).
The “borrowed” host ID bit can have a value of either 0 or 1, allowing two
subnets; 192.168.1.0 /25 and 192.168.100.128 /25.
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Appendix D IP Addresses and Subnetting
The following figure shows the company network after subnetting. There are now
two sub-networks, A and B.
Figure 120 Subnetting Example: After Subnetting
In a 25-bit subnet the host ID has 7 bits, so each sub-network has a maximum of
7
2
– 2 or 126 possible hosts (a host ID of all zeroes is the subnet’s address itself,
all ones is the subnet’s broadcast address).
192.168.1.0 with mask 255.255.255.128 is subnet A itself, and 192.168.100.127
with mask 255.255.255.128 is its broadcast address. Therefore, the lowest IP
address that can be assigned to an actual host for subnet A is 192.168.100.1 and
the highest is 192.168.100.126.
Similarly, the host ID range for subnet B is 192.168.100.129 to 192.168.1.254.
Example: Four Subnets
The previous example illustrated using a 25-bit subnet mask to divide a 24-bit
address into two subnets. Similarly, to divide a 24-bit address into four subnets,
you need to “borrow” two host ID bits to give four possible combinations (00, 01,
10 and 11). The subnet mask is 26 bits
(11111111.11111111.11111111.11000000) or 255.255.255.192.
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Appendix D IP Addresses and Subnetting
Each subnet contains 6 host ID bits, giving 26 - 2 or 62 hosts for each subnet (a
host ID of all zeroes is the subnet itself, all ones is the subnet’s broadcast
address).
Table 75 Subnet 1
IP/SUBNET MASK NETWORK NUMBER
IP Address (Decimal) 192.168.1. 0
IP Address (Binary) 11000000.10101000.00000001. 00000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address:
192.168.1.0
Broadcast Address:
192.168.1.63
Lowest Host ID: 192.168.100.1
Highest Host ID: 192.168.1.62
LAST OCTET BIT
VALUE
Table 76 Subnet 2
IP/SUBNET MASK NETWORK NUMBER
IP Address 192.168.1. 64
IP Address (Binary) 11000000.10101000.00000001. 01000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address:
192.168.1.64
Broadcast Address:
192.168.100.127
Lowest Host ID: 192.168.1.65
Highest Host ID: 192.168.100.126
LAST OCTET BIT
VALUE
Table 77 Subnet 3
IP/SUBNET MASK NETWORK NUMBER
IP Address 192.168.1. 128
IP Address (Binary) 11000000.10101000.00000001. 10000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address:
192.168.100.128
Broadcast Address:
192.168.100.191
Lowest Host ID: 192.168.100.129
Highest Host ID: 192.168.100.190
LAST OCTET BIT
VALUE
Table 78 Subnet 4
IP/SUBNET MASK NETWORK NUMBER
IP Address 192.168.1. 192
IP Address (Binary) 11000000.10101000.00000001. 11000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address:
192.168.100.192
Broadcast Address:
192.168.1.255
Lowest Host ID: 192.168.100.193
Highest Host ID: 192.168.1.254
LAST OCTET BIT
VALUE
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Appendix D IP Addresses and Subnetting
Example: Eight Subnets
Similarly, use a 27-bit mask to create eight subnets (000, 001, 010, 011, 100,
101, 110 and 111).
The following table shows IP address last octet values for each subnet.
Table 79 Eight Subnets
SUBNET
1 0 1 30 31
2 32 33 62 63
3 64 65 94 95
4 96 97 126 127
5 128 129 158 159
6 160 161 190 191
7 192 193 222 223
8 224 225 254 255
SUBNET
ADDRESS
FIRST ADDRESS
LAST
ADDRESS
BROADCAST
ADDRESS
Subnet Planning
The following table is a summary for subnet planning on a network with a 24-bit
network number.
Table 80 24-bit Network Number Subnet Planning
NO. “BORROWED”
HOST BITS
1 255.255.255.128 (/25) 2 126
2 255.255.255.192 (/26) 4 62
3 255.255.255.224 (/27) 8 30
4 255.255.255.240 (/28) 16 14
5 255.255.255.248 (/29) 32 6
6 255.255.255.252 (/30) 64 2
7 255.255.255.254 (/31) 128 1
The following table is a summary for subnet planning on a network with a 16-bit
network number.
Table 81 16-bit Network Number Subnet Planning
NO. “BORROWED”
HOST BITS
1 255.255.128.0 (/17) 2 32766
2 255.255.192.0 (/18) 4 16382
SUBNET MASK NO. SUBNETS
SUBNET MASK NO. SUBNETS
NO. HOSTS PER
SUBNET
NO. HOSTS PER
SUBNET
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Appendix D IP Addresses and Subnetting
Table 81 16-bit Network Number Subnet Planning (continued)
NO. “BORROWED”
HOST BITS
3 255.255.224.0 (/19) 8 8190
4 255.255.240.0 (/20) 16 4094
5 255.255.248.0 (/21) 32 2046
6 255.255.252.0 (/22) 64 1022
7 255.255.254.0 (/23) 128 510
8 255.255.255.0 (/24) 256 254
9 255.255.255.128 (/25) 512 126
10 255.255.255.192 (/26) 1024 62
11 255.255.255.224 (/27) 2048 30
12 255.255.255.240 (/28) 4096 14
13 255.255.255.248 (/29) 8192 6
14 255.255.255.252 (/30) 16384 2
15 255.255.255.254 (/31) 32768 1
SUBNET MASK NO. SUBNETS
NO. HOSTS PER
SUBNET
Configuring IP Addresses
Where you obtain your network number depends on your particular situation. If
the ISP or your network administrator assigns you a block of registered IP
addresses, follow their instructions in selecting the IP addresses and the subnet
mask.
If the ISP did not explicitly give you an IP network number, then most likely you
have a single user account and the ISP will assign you a dynamic IP address when
the connection is established. If this is the case, it is recommended that you select
a network number from 192.168.0.0 to 192.168.255.0. The Internet Assigned
Number Authority (IANA) reserved this block of addresses specifically for private
use; please do not use any other number unless you are told otherwise. Y ou must
also enable Network Address Translation (NAT) on the WiMAX Modem.
Once you have decided on the network nu mber, pick an IP address for your WiMAX
Modem that is easy to remember (for instance, 192.168.100.1) but make sure
that no other device on your network is using that IP address.
The subnet mask specifies the network number portion of an IP address. Your
WiMAX Modem will compute the subnet mask automatically based on the IP
address that you entered. Y ou don't need to change the subnet mask computed by
the WiMAX Modem unless you are instructed to do otherwise.
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Appendix D IP Addresses and Subnetting
Private IP Addresses
Every machine on the Internet must have a unique address. If your networks are
isolated from the Internet (running only between two branch offices, for example)
you can assign any IP addresses to the hosts without problems. However, the
Internet Assigned Numbers Authority (IANA) has reserved the following three
blocks of IP addresses specifically for private networks:
• 10.0.0.0 — 10.255.255.255
• 172.16.0.0 — 172.31.255.255
• 192.168.0.0 — 192.168.255.255
You can obtain your IP address from the IANA, from an ISP, or it can be assigned
from a private network. If you belong to a small organization and your Internet
access is through an ISP, the ISP can provide you with the Internet addresses for
your local networks. On the other hand, if you are part of a much larger
organization, you should consult your network administrator for the appropriate IP
addresses.
Regardless of your particular situation, do not create an arbitrary IP address;
always follow the guidelines above. For more information on address assignment,
please refer to RFC 1597, Address Allocation for Private Internets and RFC 1466,
Guidelines for Management of IP Address Space.
IP Address Conflicts
Each device on a network must have a unique IP address. Devices with duplicate
IP addresses on the same network will not be able to access the Internet or other
resources. The devices may also be unreachable through the network.
Conflicting Computer IP Addresses Example
More than one device can not use the same IP address. In the following example
computer A has a static (or fixed) IP address that is the same as the IP address
that a DHCP server assigns to computer B which is a DHCP client. Neither can
access the Internet. This problem can be solved by assigning a different static IP
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address to computer A or setting computer A to obtain an IP address
automatically.
Figure 121 Conflicting Computer IP Ad dresses Example
Conflicting Router IP Addresses Example
Appendix D IP Addresses and Subnetting
Since a router connects different networks, it must have interfaces using different
network numbers. For example, if a router is set between a LAN and the Internet
(WAN), the router’ s LAN and WAN addresses must be on different subnets. In the
following example, the LAN and WAN are on the same subnet. The LAN computers
cannot access the Internet because the router cannot route between networks.
Figure 122 Conflicting Computer IP Ad dresses Example
Conflicting Computer and Router IP Addresses Example
More than one device can not use the same IP address. In the following example,
the computer and the router’s LAN port both use 192.168.100.1 as the IP address.
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Appendix D IP Addresses and Subnetting
The computer cannot access the Internet. This problem can be solved by
assigning a different IP address to the computer or the router’s LAN port.
Figure 123 Conflicting Computer and Router IP Addresses Example
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APPENDIX E
Importing Certificates
This appendix shows you how to import public key certificates into your web
browser.
Public key certificates are used by web browsers to ensure that a secure web site
is legitimate. When a certificate authority such as VeriSign, Comodo, or Network
Solutions, to name a few, receives a certificate request from a website operator,
they confirm that the web domain and contact information in the request match
those on public record with a domain name registrar. If they match, then the
certificate is issued to the website operator, who then places it on the site to be
issued to all visiting web browsers to let them know that the site is legitimate.
Many ZyXEL products, such as the NSA-2401, issue their own public key
certificates. These can be used by web browsers on a LAN or WAN to verify that
they are in fact connecting to the legitimate device and not one masquerading as
it. However, because the certificates were not issued by one of the several
organizations officially recognized by the most common web browsers, you will
need to import the ZyXEL-created certificate into your web browser and flag that
certificate as a trusted authority.
User’s Guide
Note: You can see if you are browsing on a secure website if the URL in your web
browser’s address bar begins with https:// or there is a sealed padlock
icon ( ) somewhere in the main browser window (not all browsers show the
padlock in the same location.)
In this appendix, you can import a public key certificate for:
• Internet Explorer on page 242
•Firefox on page 252
•Opera on page 258
• Konqueror on page 266
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Appendix E Importing Certificates
Internet Explorer
The following example uses Microsoft Internet Explorer 7 on Windows XP
Professional; however, they can also apply to Internet Explorer on Windows Vista.
1 If your device’s web configur ator is set t o use SSL c ertification, t hen the first time
you browse to it you are presented with a certification error.
Figure 124 Internet Explorer 7: Certification Error
2 Click Continue to this website (not recommended).
Figure 125 Internet Explorer 7: Certification Error
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Appendix E Importing Certificates
3 In the Address Bar, click Certificate Error > View certificates.
Figure 126 Internet Explorer 7: Certificate Error
4 In the Certificate dialog box, click Install Certificate.
Figure 127 Internet Explorer 7: Certificate
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Appendix E Importing Certificates
5 In the Certificate Import Wizard, click Next.
Figure 128 Internet Explorer 7: Certificate Import Wizard
6 If you want Internet Explorer to Automatically select certificate store based
on the type of certificate, click Next again and then go to step 9.
Figure 129 Internet Explorer 7: Certificate Import Wizard
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Appendix E Importing Certificates
7 Otherwise, select Place all certificates in the following store and then click
Browse.
Figure 130 Internet Explorer 7: Certificate Import Wizard
8 In the Select Certificate Store dialog box, choose a location in which to save the
certificate and then click OK.
Figure 131 Internet Explorer 7: Select Certificate Store
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Appendix E Importing Certificates
9 In the Completing the Certificate Import Wizard screen, click Finish.
Figure 132 Internet Explorer 7: Certificate Import Wizard
10 If you are presented with another Security Warning, click Yes.
Figure 133 Internet Explorer 7: Security Warning
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Appendix E Importing Certificates
11 Finally, click OK when presented with the successful certificate installation
message.
Figure 134 Internet Explorer 7: Certificate Import Wizard
12 The next time you start Internet Explorer and go to a ZyXEL web configurator
page, a sealed padlock icon appears in the address bar. Click it to view the page’s
Website Identification information.
Figure 135 Internet Explorer 7: Website Identification
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Appendix E Importing Certificates
Installing a Stand-Alone Certificate File in Internet Explorer
Rather than browsing to a ZyXEL web configurator and installing a public key
certificate when prompted, you can install a stand-alone certificate file if one has
been issued to you.
1 Double-click the public key certificate file.
Figure 136 Internet Explorer 7: Public Key Certificate File
2 In the security warning dialog box, click Open.
Figure 137 Internet Explorer 7: Open File - Security Warning
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3 Refer to steps 4-12 in the Internet Explorer procedure beginning on page 242 to
complete the installation process.
User’s Guide
Removing a Certificate in Internet Explorer
This section shows you how to remove a public key certificate in Internet Explorer
7.
1 Open Internet Explorer and click TOOLS > Internet Options.
Figure 138 Internet Explorer 7: Tools Menu
Appendix E Importing Certificates
2 In the Internet Options dialog box, click Content > Certificates.
Figure 139 Internet Explorer 7: Internet Options
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