ZyAIR G-2000 Plus User’s Guide
Chapter 14 Firewalls
188
14.5.5 Upper Layer Protocols
Some higher layer protocols (such as FTP and RealAudio) utilize multiple network
connections simultaneously. In general terms, they usually have a "control connection" which
is used for sending commands between endpoints, and then "data connections" which are used
for transmitting bulk information.
Consider the FTP protocol. A user on the LAN opens a control connection to a server on the
Internet and requests a file. At this point, the remote server will open a data connection from
the Internet. For FTP to work properly, this connection must be allowed to pass through even
though a connection from the Internet would normally be rejected.
In order to achieve this, the ZyAIR inspects the application-level FTP data. Specifically, it
searches for outgoing "PORT" commands, and when it sees these; it adds a cache entry for the
anticipated data connection. This can be done safely, since the PORT command contains
address and port information, which can be used to uniquely identify the connection.
Any protocol that operates in this way must be supported on a case-by-case basis. You can use
the web configurator’s
Custom Services
feature to do this.
14.6 Guidelines For Enhancing Security With Your Firewall
1
Change the default password via SMT or web configurator.
2
Think about access control before you connect a console port to the network in any way,
including attaching a modem to the port. Be aware that a break on the console port might
give unauthorized individuals total control of the firewall, even with access control
configured.
3
Limit who can telnet into your router.
4
Don't enable any local service (such as SNMP or NTP) that you don't use. Any enabled
service could present a potential security risk. A determined hacker might be able to find
creative ways to misuse the enabled services to access the firewall or the network.
5
For local services that are enabled, protect against misuse. Protect by configuring the
services to communicate only with specific peers, and protect by configuring rules to
block packets for the services at specific interfaces.
6
Protect against IP spoofing by making sure the firewall is active.
7
Keep the firewall in a secured (locked) room.
14.7 Packet Filtering Vs Firewall
Below are some comparisons between the ZyAIR’s filtering and firewall functions.
Summary of Contents for ZyAIR G-2000 Plus
Page 1: ...ZyAIR G 2000 Plus 802 11g Wireless 4 port Router User s Guide Version 3 60 12 2004...
Page 2: ......
Page 8: ...ZyAIR G 2000 Plus User s Guide 7 Customer Support...
Page 22: ...ZyAIR G 2000 Plus User s Guide 21 Table of Contents...
Page 36: ...ZyAIR G 2000 Plus User s Guide 35 Preface...
Page 44: ...ZyAIR G 2000 Plus User s Guide 43 Chapter 1 Getting to Know Your ZyAIR...
Page 88: ...ZyAIR G 2000 Plus User s Guide 87 Chapter 6 Wireless Configuration and Roaming...
Page 124: ...ZyAIR G 2000 Plus User s Guide 123 Chapter 8 Internal RADIUS Server...
Page 156: ...ZyAIR G 2000 Plus User s Guide 155 Chapter 11 Static Route Screens...
Page 192: ...ZyAIR G 2000 Plus User s Guide 191 Chapter 14 Firewalls...
Page 210: ...ZyAIR G 2000 Plus User s Guide 209 Chapter 15 Firewall Screens...
Page 214: ...ZyAIR G 2000 Plus User s Guide 213 Chapter 16 Content Filtering...
Page 221: ...ZyAIR G 2000 Plus User s Guide Chapter 17 Certificates 220 Figure 93 My Certificate Create...
Page 224: ...ZyAIR G 2000 Plus User s Guide 223 Chapter 17 Certificates Figure 94 My Certificate Details...
Page 230: ...ZyAIR G 2000 Plus User s Guide 229 Chapter 17 Certificates Figure 97 Trusted CA Details...
Page 235: ...ZyAIR G 2000 Plus User s Guide Chapter 18 Log Screens 234 Figure 99 Log Settings...
Page 240: ...ZyAIR G 2000 Plus User s Guide 239 Chapter 18 Log Screens...
Page 252: ...ZyAIR G 2000 Plus User s Guide 251 Chapter 19 Maintenance Figure 114 Restart Screen...
Page 264: ...ZyAIR G 2000 Plus User s Guide 263 Chapter 22 Menu 2 WAN Setup...
Page 274: ...ZyAIR G 2000 Plus User s Guide 273 Chapter 23 LAN Setup...
Page 280: ...ZyAIR G 2000 Plus User s Guide 279 Chapter 24 Internet Access...
Page 290: ...ZyAIR G 2000 Plus User s Guide 289 Chapter 25 Remote Node Configuration...
Page 338: ...ZyAIR G 2000 Plus User s Guide 337 Chapter 32 System Security...
Page 350: ...ZyAIR G 2000 Plus User s Guide 349 Chapter 33 System Information and Diagnosis...
Page 362: ...ZyAIR G 2000 Plus User s Guide 361 Chapter 34 Firmware and Configuration File Maintenance...
Page 376: ...ZyAIR G 2000 Plus User s Guide 375 Chapter 37 Call Scheduling...
Page 380: ...ZyAIR G 2000 Plus User s Guide 379 Appendix B...
Page 392: ...ZyAIR G 2000 Plus User s Guide 391 Appendix C...
Page 396: ...ZyAIR G 2000 Plus User s Guide 395 Appendix D...
Page 404: ...ZyAIR G 2000 Plus User s Guide 403 Appendix E...
Page 406: ...ZyAIR G 2000 Plus User s Guide 405 Appendix F...
Page 413: ...ZyAIR G 2000 Plus User s Guide Appendix H 412 Figure 235 ESS Provides Campus Wide Coverage...
Page 414: ...ZyAIR G 2000 Plus User s Guide 413 Appendix H...
Page 418: ...ZyAIR G 2000 Plus User s Guide 417 Appendix I...
Page 430: ...ZyAIR G 3000 User s Guide 429 Index ZyNOS F W Version 351 ZyXEL s Firewall Introduction 179...