Private Ip Addresses; Dns Server Address; Syslog; Nat - ZyXEL Communications ZyXEL Vantage VSG-1000 User Manual

VSG-1000 Vantage Service Gateway
4.4.2

Private IP Addresses

Every machine on the Internet must have a unique address. If your networks are isolated from the Internet, for
example, only between your two branch offices, 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
172.16.0.0
192.168.0.0
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.

4.5 DNS Server Address

DNS (Domain Name System) is for mapping a domain name to its corresponding IP address and vice versa, for
example, the IP address of www.zyxel.com is 204.217.0.2. The DNS server is extremely important because without
it, you must know the IP address of a machine before you can access it. The DNS server addresses that you enter in
the DHCP setup are passed to the client machines along with the assigned IP address and subnet mask.
There are two ways that an ISP disseminates the DNS server addresses. The first is for an ISP to tell a customer the
DNS server addresses, usually in the form of an information sheet, when s/he signs up. The second is to obtain the
DNS server information automatically when a computer is set as a DHCP client.

4.6 Syslog

Your VSG sends logs to an external server used to store logs. The logs contain the current user information such as
the MAC address and IP address. The syslog format is as follows.
Log format: <166 Information>
[System Time yy/mm/dd/hh/mm/ss, System IP, System Name, username1, user's IP,
user's MAC, username2...]
Refer to Table 4-7 for descriptions of system logs you may select in the System Configuration screen.

4.7 NAT

NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address of a host in a packet, for
example, the source address of an outgoing packet, used within one network to a different IP address known within
another network.
4.7.1

NAT Definitions

Inside/outside denotes where a host is located relative to the VSG, for example, the computers of your subscribers
are the inside hosts, while the web servers on the Internet are the outside hosts.
Global/local denotes the IP address of a host in a packet as the packet traverses a router, for example, the local
address refers to the IP address of a host when the packet is in the local network, while the global address refers to
the IP address of the host when the same packet is traveling in the WAN side.
Note that inside/outside refers to the location of a host, while global/local refers to the IP address of a host used in a
packet. Thus, an inside local address (ILA) is the IP address of an inside host in a packet when the packet is still in
4-2
— 10.255.255.255
— 172.31.255.255
— 192.168.255.255
System Configuration