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Appendix D Wireless LANs
P-661HNU-Fx User’s Guide
356
In step 3, you add another access point (
AP2
) to your network.
AP2
is out of
range of
AP1
, so you cannot use
AP1
for the WPS handshake with the new access
point. However, you know that
Client 2
supports the registrar function, so you use
it to perform the WPS handshake instead.
Figure 199
WPS: Example Network Step 3
Limitations of WPS
WPS has some limitations of which you should be aware.
WPS works in Infrastructure networks only (where an AP and a wireless client
communicate). It does not work in Ad-Hoc networks (where there is no AP).
When you use WPS, it works between two devices only. You cannot enroll
multiple devices simultaneously, you must enroll one after the other.
For instance, if you have two enrollees and one registrar you must set up the
first enrollee (by pressing the WPS button on the registrar and the first enrollee,
for example), then check that it successfully enrolled, then set up the second
device in the same way.
WPS works only with other WPS-enabled devices. However, you can still add
non-WPS devices to a network you already set up using WPS.
WPS works by automatically issuing a randomly-generated WPA-PSK or WPA2-
PSK pre-shared key from the registrar device to the enrollee devices. Whether
the network uses WPA-PSK or WPA2-PSK depends on the device. You can check
the configuration interface of the registrar device to discover the key the
network is using (if the device supports this feature). Then, you can enter the
key into the non-WPS device and join the network as normal (the non-WPS
device must also support WPA-PSK or WPA2-PSK).
CLIENT 1
AP1
REGISTRAR
CLIENT 2
EXISTING CONNECTION
SECURITY INFO
ENROLLEE
AP1
EXISTING CONNECTION
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357
When you use the PBC method, there is a short period (from the moment you
press the button on one device to the moment you press the button on the
other device) when any WPS-enabled device could join the network. This is
because the registrar has no way of identifying the “correct” enrollee, and
cannot differentiate between your enrollee and a rogue device. This is a possible
way for a hacker to gain access to a network.
You can easily check to see if this has happened. WPS works between only two
devices simultaneously, so if another device has enrolled your device will be
unable to enroll, and will not have access to the network. If this happens, open
the access point’s configuration interface and look at the list of associated
clients (usually displayed by MAC address). It does not matter if the access
point is the WPS registrar, the enrollee, or was not involved in the WPS
handshake; a rogue device must still associate with the access point to gain
access to the network. Check the MAC addresses of your wireless clients
(usually printed on a label on the bottom of the device). If there is an unknown
MAC address you can remove it or reset the AP.
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359
A
PPENDIX
E
Common Services
The following table lists some commonly-used services and their associated
protocols and port numbers. For a comprehensive list of port numbers, ICMP type/
code numbers and services, visit the IANA (Internet Assigned Number Authority)
web site.
Name
: This is a short, descriptive name for the service. You can use this one or
create a different one, if you like.
Protocol
: This is the type of IP protocol used by the service. If this is
TCP/
UDP
, then the service uses the same port number with TCP and UDP. If this is
USER-DEFINED
, the
Port(s
) is the IP protocol number, not the port number.
Port(s)
: This value depends on the
Protocol
. Please refer to RFC 1700 for
further information about port numbers.
• If the
Protocol
is
TCP
,
UDP
, or
TCP/UDP
, this is the IP port number.
• If the
Protocol
is
USER
, this is the IP protocol number.
Description
: This is a brief explanation of the applications that use this service
or the situations in which this service is used.
Table 101
Commonly Used Services
NAME
PROTOCOL
PORT(S)
DESCRIPTION
AH
(IPSEC_TUNNEL)
User-Defined
51
The IPSEC AH (Authentication
Header) tunneling protocol uses this
service.
AIM/New-ICQ
TCP
5190
AOL’s Internet Messenger service. It
is also used as a listening port by
ICQ.
AUTH
TCP
113
Authentication protocol used by some
servers.
BGP
TCP
179
Border Gateway Protocol.
BOOTP_CLIENT
UDP
68
DHCP Client.
BOOTP_SERVER
UDP
67
DHCP Server.
CU-SEEME
TCP
UDP
7648
24032
A popular videoconferencing solution
from White Pines Software.
DNS
TCP/UDP
53
Domain Name Server, a service that
matches web names (for example
www.zyxel.com
) to IP numbers.
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Appendix E Common Services
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360
ESP
(IPSEC_TUNNEL)
User-Defined
50
The IPSEC ESP (Encapsulation
Security Protocol) tunneling protocol
uses this service.
FINGER
TCP
79
Finger is a UNIX or Internet related
command that can be used to find out
if a user is logged on.
FTP
TCP
TCP
20
21
File Transfer Program, a program to
enable fast transfer of files, including
large files that may not be possible by
e-mail.
H.323
TCP
1720
NetMeeting uses this protocol.
HTTP
TCP
80
Hyper Text Transfer Protocol - a
client/server protocol for the world
wide web.
HTTPS
TCP
443
HTTPS is a secured http session often
used in e-commerce.
ICMP
User-Defined
1
Internet Control Message Protocol is
often used for diagnostic or routing
purposes.
ICQ
UDP
4000
This is a popular Internet chat
program.
IGMP
(MULTICAST)
User-Defined
2
Internet Group Management Protocol
is used when sending packets to a
specific group of hosts.
IKE
UDP
500
The Internet Key Exchange algorithm
is used for key distribution and
management.
IRC
TCP/UDP
6667
This is another popular Internet chat
program.
MSN Messenger
TCP
1863
Microsoft Networks’ messenger
service uses this protocol.
NEW-ICQ
TCP
5190
An Internet chat program.
NEWS
TCP
144
A protocol for news groups.
NFS
UDP
2049
Network File System - NFS is a client/
server distributed file service that
provides transparent file sharing for
network environments.
NNTP
TCP
119
Network News Transport Protocol is
the delivery mechanism for the
USENET newsgroup service.
PING
User-Defined
1
Packet INternet Groper is a protocol
that sends out ICMP echo requests to
test whether or not a remote host is
reachable.
POP3
TCP
110
Post Office Protocol version 3 lets a
client computer get e-mail from a
POP3 server through a temporary
connection (TCP/IP or other).
Table 101
Commonly Used Services (continued)
NAME
PROTOCOL
PORT(S)
DESCRIPTION

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