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The SIP Proxy, Option, IP Rules for Media Data, Record-Route

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6.2.8. The SIP ALG Chapter 6. Security Mechanisms Data Channel Timeout Allow Media Bypass value is 43200 seconds. The maximum time allowed for periods with no traffic in a SIP session. A timeout condition occurs if this value is exceeded. The default value is 120 seconds. If this option is enabled then data. such as RTP/RTCP communication, may take place directly between two clients without involving the NetDefend Firewall. This would only happen if the two clients were behind the same interface and belong to the same network. The default value is Disabled. The SIP Proxy Record-Route Option To understand how to set up SIP scenarios with NetDefendOS, it is important to first understand the SIP proxy Record-Route option. SIP proxies have the Record-Route option either enabled or disabled. When it is switched on, a proxy is known as a Stateful proxy. When Record-Route is enabled, a proxy is saying it will be the intermediary for all SIP signalling that takes place between two clients. When a SIP session is being set up, the calling client sends an INVITE message to its outbound SIP proxy server. The SIP proxy relays this message to the remote proxy server responsible for the called, remote client's contact information. The remote proxy then relays the INVITE message to the called client. Once the two clients have learnt of each other's IP addresses, they can communicate directly with each other and remaining SIP messages can bypass the proxies. This facilitates scaling since proxies are used only for the initial SIP message exchange. The disadvantage of removing proxies from the session is that NetDefendOS IP rules must be set up to allow all SIP messages through the NetDefend Firewall, and if the source network of the messages is not known then a large number of potentially dangerous connections must be allowed by the IP rule set. This problem does not occur if the local proxy is set up with the Record-Route option enabled. In this mode, all SIP messages will only come from the proxy. The different rules required when the Record-Route option is enabled and disabled can be seen in the two different sets of IP rules listed below in the detailed description of Scenario 1 Protecting local clients - Proxy located on the Internet. IP Rules for Media Data When discussing SIP data flows there are two distinct types of exchanges involved: • The SIP session which sets up communication between two clients prior to the exchange of media data. • The exchange of the media data itself, for example the coded voice data which constitute a VoIP phone call. In the SIP setups described below, IP rules need only be explicitly defined to deal with the first of the above, the SIP exchanges needed for establishing client-to-client communications. No IP rules or other objects need to be defined to handle the second of the above, the exchange of media data. The SIP ALG automatically and invisibly takes care of creating the connections required (sometimes described as SIP pinholes) for allowing the media data traffic to flow through the NetDefend Firewall. Tip Make sure there are no preceding rules already in the IP rule set disallowing or allowing the same kind of traffic. 294

Section	Page
User Manual	3
Table of Contents	4
Preface	15
Chapter 1. NetDefendOS Overview	17
1.1. Features	17
1.2. NetDefendOS Architecture	20
1.2.1. State-based Architecture	20
1.2.2. NetDefendOS Building Blocks	20
1.2.3. Basic Packet Flow	21
1.3. NetDefendOS State Engine Packet Flow	24
Chapter 2. Management and Maintenance	29
2.1. Managing NetDefendOS	29
2.1.1. Overview	29
2.1.2. The Default Administrator Account	30
2.1.3. The Web Interface	30
2.1.4. The CLI	36
2.1.5. CLI Scripts	44
2.1.6. Secure Copy	48
2.1.7. The Console Boot Menu	50
2.1.8. Management Advanced Settings	52
2.1.9. Working with Configurations	53
2.2. Events and Logging	59
2.2.1. Overview	59
2.2.2. Log Messages	59
2.2.3. Creating Log Receivers	60
2.2.4. Logging to MemoryLogReceiver	60
2.2.5. Logging to Syslog Hosts	60
2.2.6. Severity Filter and Message Exceptions	62
2.2.7. SNMP Traps	62
2.2.8. Advanced Log Settings	64
2.3. RADIUS Accounting	65
2.3.1. Overview	65
2.3.2. RADIUS Accounting Messages	65
2.3.3. Interim Accounting Messages	67
2.3.4. Activating RADIUS Accounting	67
2.3.5. RADIUS Accounting Security	68
2.3.6. RADIUS Accounting and High Availability	68
2.3.7. Handling Unresponsive RADIUS Servers	68
2.3.8. Accounting and System Shutdowns	69
2.3.9. Limitations with NAT	69
2.3.10. RADIUS Advanced Settings	69
2.4. Monitoring	71
2.4.1. The Link Monitor	71
2.4.2. SNMP Monitoring	73
2.4.3. Hardware Monitoring	76
2.4.4. Memory Monitoring Settings	78
2.5. The pcapdump Command	80
2.6. Maintenance	83
2.6.1. Auto-Update Mechanism	83
2.6.2. Backing Up Configurations	83
2.6.3. Restore to Factory Defaults	85
Chapter 3. Fundamentals	88
3.1. The Address Book	88
3.1.1. Overview	88
3.1.2. IP Addresses	88
3.1.3. Ethernet Addresses	90
3.1.4. Address Groups	91
3.1.5. Auto-Generated Address Objects	92
3.1.6. Address Book Folders	92
3.2. IPv6 Support	93
3.3. Services	98
3.3.1. Overview	98
3.3.2. Creating Custom Services	99
3.3.3. ICMP Services	102
3.3.4. Custom IP Protocol Services	104
3.3.5. Service Groups	104
3.3.6. Custom Service Timeouts	105
3.4. Interfaces	106
3.4.1. Overview	106
3.4.2. Ethernet Interfaces	108
3.4.2.1. Useful CLI Commands for Ethernet Interfaces	112
3.4.3. VLAN	115
3.4.4. PPPoE	118
3.4.5. GRE Tunnels	120
3.4.6. Interface Groups	124
3.5. ARP	126
3.5.1. Overview	126
3.5.2. The NetDefendOS ARP Cache	126
3.5.3. Creating ARP Objects	128
3.5.4. Using ARP Advanced Settings	130
3.5.5. ARP Advanced Settings Summary	131
3.6. IP Rules	135
3.6.1. Security Policies	135
3.6.2. IP Rule Evaluation	138
3.6.3. IP Rule Actions	139
3.6.4. Editing IP rule set Entries	140
3.6.5. IP Rule Set Folders	141
3.6.6. Configuration Object Groups	142
3.7. Schedules	146
3.8. Certificates	148
3.8.1. Overview	148
3.8.2. Certificates in NetDefendOS	150
3.8.3. CA Certificate Requests	151
3.9. Date and Time	153
3.9.1. Overview	153
3.9.2. Setting Date and Time	153
3.9.3. Time Servers	154
3.9.4. Settings Summary for Date and Time	157
3.10. DNS	160
Chapter 4. Routing	164
4.1. Overview	164
4.2. Static Routing	165
4.2.1. The Principles of Routing	165
4.2.2. Static Routing	169
4.2.3. Route Failover	174
4.2.4. Host Monitoring for Route Failover	177
4.2.5. Advanced Settings for Route Failover	179
4.2.6. Proxy ARP	180
4.3. Policy-based Routing	183
4.4. Route Load Balancing	190
4.5. OSPF	196
4.5.1. Dynamic Routing	196
4.5.2. OSPF Concepts	199
4.5.3. OSPF Components	204
4.5.3.1. OSPF Router Process	204
4.5.3.2. OSPF Area	206
4.5.3.3. OSPF Interface	207
4.5.3.4. OSPF Neighbors	209
4.5.3.5. OSPF Aggregates	209
4.5.3.6. OSPF VLinks	209
4.5.4. Dynamic Routing Rules	210
4.5.4.1. Overview	210
4.5.4.2. Dynamic Routing Rule	212
4.5.4.3. OSPF Action	212
4.5.4.4. Routing Action	213
4.5.5. Setting Up OSPF	213
4.5.6. An OSPF Example	217
4.6. Multicast Routing	220
4.6.1. Overview	220
4.6.2. Multicast Forwarding with SAT Multiplex Rules	221
4.6.2.1. Multicast Forwarding - No Address Translation	221
4.6.2.2. Multicast Forwarding - Address Translation Scenario	224
4.6.3. IGMP Configuration	225
4.6.3.1. IGMP Rules Configuration - No Address Translation	227
4.6.3.2. IGMP Rules Configuration - Address Translation	228
4.6.4. Advanced IGMP Settings	230
4.7. Transparent Mode	233
4.7.1. Overview	233
4.7.2. Enabling Internet Access	238
4.7.3. Transparent Mode Scenarios	239
4.7.4. Spanning Tree BPDU Support	243
4.7.5. Advanced Settings for Transparent Mode	244
Chapter 5. DHCP Services	249
5.1. Overview	249
5.2. DHCP Servers	250
5.2.1. Static DHCP Hosts	253
5.2.2. Custom Options	255
5.3. DHCP Relaying	256
5.3.1. DHCP Relay Advanced Settings	257
5.4. IP Pools	259
Chapter 6. Security Mechanisms	263
6.1. Access Rules	263
6.1.1. Overview	263
6.1.2. IP Spoofing	264
6.1.3. Access Rule Settings	264
6.2. ALGs	266
6.2.1. Overview	266
6.2.2. The HTTP ALG	267
6.2.3. The FTP ALG	270
6.2.4. The TFTP ALG	279
6.2.5. The SMTP ALG	280
6.2.5.1. Anti-Spam Filtering	283
6.2.6. The POP3 ALG	289
6.2.7. The PPTP ALG	290
6.2.8. The SIP ALG	291
6.2.9. The H.323 ALG	302
6.2.10. The TLS ALG	316
6.3. Web Content Filtering	319
6.3.1. Overview	319
6.3.2. Active Content Handling	319
6.3.3. Static Content Filtering	320
6.3.4. Dynamic Web Content Filtering	322
6.3.4.1. Overview	322
6.3.4.2. Setting Up WCF	323
6.3.4.3. Content Filtering Categories	327
6.3.4.4. Customizing WCF HTML Pages	334
6.4. Anti-Virus Scanning	337
6.4.1. Overview	337
6.4.2. Implementation	337
6.4.3. Activating Anti-Virus Scanning	338
6.4.4. The Signature Database	338
6.4.5. Subscribing to the D-Link Anti-Virus Service	339
6.4.6. Anti-Virus Options	339
6.5. Intrusion Detection and Prevention	343
6.5.1. Overview	343
6.5.2. IDP Availability for D-Link Models	343
6.5.3. IDP Rules	345
6.5.4. Insertion/Evasion Attack Prevention	347
6.5.5. IDP Pattern Matching	348
6.5.6. IDP Signature Groups	349
6.5.7. IDP Actions	350
6.5.8. SMTP Log Receiver for IDP Events	351
6.6. Denial-of-Service Attack Prevention	355
6.6.1. Overview	355
6.6.2. DoS Attack Mechanisms	355
6.6.3. Ping of Death and Jolt Attacks	355
6.6.4. Fragmentation overlap attacks: Teardrop, Bonk, Boink and Nestea	356
6.6.5. The Land and LaTierra attacks	356
6.6.6. The WinNuke attack	356
6.6.7. Amplification attacks: Smurf, Papasmurf, Fraggle	357
6.6.8. TCP SYN Flood Attacks	358
6.6.9. The Jolt2 Attack	358
6.6.10. Distributed DoS Attacks	358
6.7. Blacklisting Hosts and Networks	360
Chapter 7. Address Translation	363
7.1. Overview	363
7.2. NAT	364
7.3. NAT Pools	369
7.4. SAT	372
7.4.1. Translation of a Single IP Address (1:1)	372
7.4.2. Translation of Multiple IP Addresses (M:N)	377
7.4.3. All-to-One Mappings (N:1)	379
7.4.4. Port Translation	381
7.4.5. Protocols Handled by SAT	381
7.4.6. Multiple SAT Rule Matches	381
7.4.7. SAT and FwdFast Rules	382
Chapter 8. User Authentication	385
8.1. Overview	385
8.2. Authentication Setup	387
8.2.1. Setup Summary	387
8.2.2. The Local Database	387
8.2.3. External RADIUS Servers	389
8.2.4. External LDAP Servers	389
8.2.5. Authentication Rules	396
8.2.6. Authentication Processing	398
8.2.7. A Group Usage Example	399
8.2.8. HTTP Authentication	399
8.3. Customizing Authentication HTML Pages	404
Chapter 9. VPN	409
9.1. Overview	409
9.1.1. VPN Usage	409
9.1.2. VPN Encryption	410
9.1.3. VPN Planning	411
9.1.4. Key Distribution	411
9.1.5. The TLS Alternative for VPN	412
9.2. VPN Quick Start	413
9.2.1. IPsec LAN to LAN with Pre-shared Keys	414
9.2.2. IPsec LAN to LAN with Certificates	415
9.2.3. IPsec Roaming Clients with Pre-shared Keys	416
9.2.4. IPsec Roaming Clients with Certificates	418
9.2.5. L2TP Roaming Clients with Pre-Shared Keys	419
9.2.6. L2TP Roaming Clients with Certificates	421
9.2.7. PPTP Roaming Clients	421
9.3. IPsec Components	423
9.3.1. Overview	423
9.3.2. Internet Key Exchange (IKE)	423
9.3.3. IKE Authentication	429
9.3.4. IPsec Protocols (ESP/AH)	430
9.3.5. NAT Traversal	431
9.3.6. Algorithm Proposal Lists	433
9.3.7. Pre-shared Keys	434
9.3.8. Identification Lists	435
9.4. IPsec Tunnels	438
9.4.1. Overview	438
9.4.2. LAN to LAN Tunnels with Pre-shared Keys	440
9.4.3. Roaming Clients	440
9.4.4. Fetching CRLs from an alternate LDAP server	445
9.4.5. Troubleshooting with ikesnoop	446
9.4.6. IPsec Advanced Settings	453
9.5. PPTP/L2TP	457
9.5.1. PPTP Servers	457
9.5.2. L2TP Servers	458
9.5.3. L2TP/PPTP Server advanced settings	463
9.5.4. PPTP/L2TP Clients	463
9.6. SSL VPN	466
9.6.1. Overview	466
9.6.2. Configuring SSL VPN in NetDefendOS	467
9.6.3. Installing the SSL VPN Client	469
9.6.4. Setup Example	472
9.7. CA Server Access	474
9.8. VPN Troubleshooting	477
9.8.1. General Troubleshooting	477
9.8.2. Troubleshooting Certificates	478
9.8.3. IPsec Troubleshooting Commands	478
9.8.4. Management Interface Failure with VPN	479
9.8.5. Specific Error Messages	479
9.8.6. Specific Symptoms	482
Chapter 10. Traffic Management	485
10.1. Traffic Shaping	485
10.1.1. Overview	485
10.1.2. Traffic Shaping in NetDefendOS	486
10.1.3. Simple Bandwidth Limiting	488
10.1.4. Limiting Bandwidth in Both Directions	489
10.1.5. Creating Differentiated Limits Using Chains	490
10.1.6. Precedences	492
10.1.7. Pipe Groups	496
10.1.8. Traffic Shaping Recommendations	499
10.1.9. A Summary of Traffic Shaping	500
10.1.10. More Pipe Examples	501
10.2. IDP Traffic Shaping	506
10.2.1. Overview	506
10.2.2. Setting Up IDP Traffic Shaping	506
10.2.3. Processing Flow	507
10.2.4. The Importance of Specifying a Network	507
10.2.5. A P2P Scenario	508
10.2.6. Viewing Traffic Shaping Objects	509
10.2.7. Guaranteeing Instead of Limiting Bandwidth	510
10.2.8. Logging	510
10.3. Threshold Rules	511
10.4. Server Load Balancing	514
10.4.1. Overview	514
10.4.2. SLB Distribution Algorithms	515
10.4.3. Selecting Stickiness	516
10.4.4. SLB Algorithms and Stickiness	517
10.4.5. Server Health Monitoring	518
10.4.6. Setting Up SLB_SAT Rules	519
Chapter 11. High Availability	523
11.1. Overview	523
11.2. HA Mechanisms	525
11.3. Setting Up HA	528
11.3.1. HA Hardware Setup	528
11.3.2. NetDefendOS Manual HA Setup	529
11.3.3. Verifying the Cluster Functions	530
11.3.4. Unique Shared Mac Addresses	531
11.4. HA Issues	532
11.5. Upgrading an HA Cluster	534
11.6. Link Monitoring and HA	536
11.7. HA Advanced Settings	537
Chapter 12. ZoneDefense	539
12.1. Overview	539
12.2. ZoneDefense Switches	540
12.3. ZoneDefense Operation	541
12.3.1. SNMP	541
12.3.2. Threshold Rules	541
12.3.3. Manual Blocking and Exclude Lists	541
12.3.4. ZoneDefense with Anti-Virus Scanning	543
12.3.5. Limitations	543
Chapter 13. Advanced Settings	546
13.1. IP Level Settings	546
13.2. TCP Level Settings	550
13.3. ICMP Level Settings	555
13.4. State Settings	556
13.5. Connection Timeout Settings	558
13.6. Length Limit Settings	560
13.7. Fragmentation Settings	562
13.8. Local Fragment Reassembly Settings	566
13.9. Miscellaneous Settings	567
Appendix A. Subscribing to Updates	570
Appendix B. IDP Signature Groups	572
Appendix C. Verified MIME filetypes	576
Appendix D. The OSI Framework	580

Match case Limit results 1 per page

value is

43200 seconds

Data Channel Timeout

The maximum time allowed for periods with no traffic in a

SIP session. A timeout condition occurs if this value is

exceeded. The default value is

120 seconds

Allow Media Bypass

If this option is enabled then data. such as RTP/RTCP

communication, may take place directly between two clients

without involving the NetDefend Firewall. This would only

happen if the two clients were behind the same interface and

belong to the same network. The default value is

Disabled

The SIP Proxy

Record-Route

Option

To understand how to set up SIP scenarios with NetDefendOS, it is important to first understand the

SIP proxy

Record-Route

option. SIP proxies have the Record-Route option either enabled or

disabled. When it is switched on, a proxy is known as a

Stateful proxy

. When Record-Route is

enabled, a proxy is saying it will be the intermediary for all SIP signalling that takes place between

two clients.

When a SIP session is being set up, the calling client sends an

INVITE

message to its outbound SIP

proxy server. The SIP proxy relays this message to the remote proxy server responsible for the

called, remote client's contact information. The remote proxy then relays the

INVITE

message to the

called client. Once the two clients have learnt of each other's IP addresses, they can communicate

directly with each other and remaining SIP messages can bypass the proxies. This facilitates scaling

since proxies are used only for the initial SIP message exchange.

The disadvantage of removing proxies from the session is that NetDefendOS IP rules must be set up

to allow all SIP messages through the NetDefend Firewall, and if the source network of the

messages is not known then a large number of potentially dangerous connections must be allowed

by the IP rule set. This problem does not occur if the local proxy is set up with the Record-Route

option enabled. In this mode, all SIP messages will only come from the proxy.

The different rules required when the

Record-Route

option is enabled and disabled can be seen in

the two different sets of IP rules listed below in the detailed description of

Scenario 1

Protecting local clients - Proxy located on the Internet

IP Rules for Media Data

When discussing SIP data flows there are two distinct types of exchanges involved:

•

The SIP session which sets up communication between two clients prior to the exchange of

media data

•

The exchange of the

media data

itself, for example the coded voice data which constitute a VoIP

phone call.

In the SIP setups described below, IP rules need only be explicitly defined to deal with the first of

the above, the SIP exchanges needed for establishing client-to-client communications. No IP rules

or other objects need to be defined to handle the second of the above, the exchange of media data.

The SIP ALG automatically and invisibly takes care of creating the connections required

(sometimes described as SIP

pinholes

) for allowing the media data traffic to flow through the

NetDefend Firewall.

Tip

Make sure there are no preceding rules already in the IP rule set disallowing or

allowing the same kind of traffic.

6.2.8. The SIP ALG

Chapter 6. Security Mechanisms

294