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Network | Listeners | Dialup
# Network LAN Addresses NATed Addresses NAT/Firewall Parameters Domain Name Resolver (DNR) IPv6 Support Network Address Lists Denied Addresses Debug Addresses CommuniGate Pro is a network server, and it needs to know the configuration of your network. Most of the settings are retrieved automatically from your OS setup, but you may want to change these settings and/or specify additional settings. This section describes the CommuniGate Pro network settings.

## Network Address Lists

Many CommuniGate Pro components use Network (IP) Address lists. These lists are specify Client and Blacklisted addresses, access restrictions for Listeners, etc.

This section describes the Network Address List format.

10.10.12.24 ; our back-up 10.10.13.32-10.10.13.191 ; our dial-ups !10.10.13.100-10.10.13.102 ; excluded addresses ; a comment line 77.177.66.166 ; our other office 64.173.55.160/27 ; 64.173.55.160-64.173.55.191 2001:470:1f01:2565::a:0/125 ; 2001:470:1f01:2565::a:0-2001:470:1f01:2565::a:7

A Network Address List is specified as multi-line text data.

Each text line should contain one of the following:

- one IP address
- an address range - two IP addresses separated with the minus (`-`) symbol: a range includes both IP addresses and all addresses between them
- an address and a numeric mask, separated with the slash (`/`) symbol.
  The mask value should be between 1 and 32 for IPv4 addresses and between 1 and 128 for IPv6 addresses. It specifies how many higher bits of the specified address are valid. The remaining lower bits of the address must be zero. The range includes all addresses with the specified higher bits.

The first IP address can be preceded with the exclamation point (`!`) symbol. In this case the specified IP address or the address range is excluded from the list composed using the preceding lines.

A comment (separated with the semicolon (`;`) symbol) the can be placed at the end of a line.
Lines starting with the semicolon symbol, and empty lines are comment lines.

## LAN Addresses

If you use CommuniGate Pro in a corporate environment, most of your users will connect to the Server from the corporate LAN(s).

Use the WebAdmin Interface to specify your LAN Addresses. Open the Network pages in the Settings realm, then open the LAN IPs page.

LAN IP Addresses
10.0.0.1-10.0.0.255 ; office LAN 10.0.1.12 ; remote office on VPN 10.0.1.15-10.0.1.220 ; DHCP LAN addresses
Server LAN IP Address:

The LAN IP Addresses table initially contains the addresses the CommuniGate Pro software retrieved from the Server OS configuration. Correct this list to include all LAN (local networks) the CommuniGate Pro Server needs to serve.
The Network Address Lists section explains the list format.

Usually, you want all E-mail and Real-Time (VoIP/IM) clients connecting from the LAN addresses to be able to relay E-mails and Signals to any Internet destination. In this case you may want to include the LAN addresses into the Client IP Addresses list.

The list of LAN IP Addresses is used to support Real-Time (voice, video, etc.) communications, so the CommuniGate Pro Server knows which addresses are belong to NAT'ed ("local") addresses, i.e. which addresses cannot be contacted directly from the Internet.

Use the Server LAN IP Address setting to select the Server own IP Address the Server OS uses to communicate with computers on the LAN.

## NATed Addresses

CommuniGate Pro can provide SIP and XIMSS signaling, and media communications for remote clients located behind NAT devices, implementing the far-end NAT traversal functionality.

See the NAT section for more details.

## NAT/Firewall Parameters

There are two main types of LAN installations:

- your CommuniGate Pro Server is installed behind a NAT/Firewall device;
  or
- your CommuniGate Pro Server has at least two network interfaces, one connected to the LAN, and one - to the Internet (WAN).

Local NAT/Firewall/Load Balancer
WAN IPv4 Address: | WAN IPv6 Address:

`WAN IPv4 Address`
  If your CommuniGate Pro Server has several network interfaces, some connecting it to the LAN, and some - to the WAN (Internet), use this setting to specify the IP address the Server OS uses by default when connecting to remote hosts over the Internet:

If your CommuniGate Pro Server is installed on a LAN behind a NAT/Firewall, the NAT/Firewall device should be configured to relay all connections on its communication (POP, SMTP, SIP, XMPP, etc.) ports to the CommuniGate Pro Server LAN address. Use this setting to specify the IP address your NAT/Firewall "relays" to CommuniGate Pro.

For example, if your CommuniGate Pro Server has the 10.0.1.12 IP address on your LAN, and the NAT/Firewall relays all incoming connections coming to the 77.77.77.77 IP address to the 10.0.1.12 address, specify the 77.77.77.77 IP address in this setting:

`WAN IPv6 Address`
  If your CommuniGate Pro Server is connected to the IPv6 network, specify the Server IP address the Server OS uses by default to connect to remote hosts over the IPv6 Internet.

## Domain Name Resolver (DNR)

Use the WebAdmin Interface to configure the Resolver settings. Open the Network pages in the Settings realm, and follow the DNS Resolver link.

Domain Name Resolver
Log Level: |  | Concurrent Requests: |
DNS Servers Addresses: |  | Source IP Address: | :
Balance Server Load: |  | Use Supplementary Responses: |
Initial Time-out: |  | Retry Limit: |

`Log Level`
  Use this setting to specify what kind of information the Domain Name Resolver should put in the Server Log. Usually you should use the `Major` or `Problems` levels. In the later case you will see the information about all failed DNS lookups. If you use the RBL services, you may see a lot of failed lookups in the Log. When you experience problems with the Domain Name Resolver, you may want to set the Log Level setting to `Low-Level` or `All Info`: in this case protocol-level or link-level details will be recorded in the System Log as well.
  The Resolver records in the System Log are marked with the `DNR` tag.
`Concurrent Requests`
  This setting limits the number of concurrent requests the Resolver can send to Domain Name Servers. On a heavily-loaded Mail or Signal relay processing many thousand requests per second, this parameter should be selected after some testing: older DNS servers may crash if requested to process too many concurrent requests.
`DNS Addresses`
  This setting specifies how the CommuniGate Pro Server selects the DNS servers to use. If the `OS-specified` option is selected, the Server reads the DNS server addresses from the Server host OS. To force the server to re-read those addresses, click the Refresh button on the General page in the Settings section.
  If the `Custom` option is selected, the CommuniGate Pro Server will use the DNS servers addresses listed in the text field next to this pop-up menu.
  If no DNS server address is specified, the CommuniGate Pro Server uses the 127.0.0.1 address, trying to connect to a DNS server that can be running on the same computer as the CommuniGate Pro Server.
`Balance Server Load`
  If this option is disabled, then the initial request is always sent to the first DNS server in the list, and if there is no response from that server, the request is resent to the second DNS server, etc.
  If this option is enabled, then initial requests are sent to different DNS servers: the first initial request is sent to the first DNS server (and if it fails - the request is resent to the second DNS server), the second initial request is sent to the second DNS server (and if it fails - the request is resent to the third DNS server), etc.
  Enable this option if your Server performs a lot of DNR operations and it can use several equally effective DNS servers.
`Use Supplementary Responses`
  If this option is enabled, then "supplementary" records in MX and SRV requests are processed. These records contain the IP addresses (A and AAAA records) for the domain names listed in an MX or SRV response, so no additional DNR request is needed to retrieve these IP addresses.
`Initial Time-out`
  The Domain Name System uses the connectionless UDP protocol by default, and if there any network trouble, a UDP request or response can be lost (while the TCP protocol automatically resends lost packets).
  The Domain Name Resolver waits for a response from a DNS server for the period of time specified with this option.
  If a response is not received, the Resolver resends the request, and waits twice longer, if it times out again, it can resend the request again and wait three times longer.
  If you have several Domain Name Servers specified, each time the resolver needs to repeat a request, it sends it to the next DNS server in the list.
`Retry Limit`
  This option specifies how many time the Resolver should re-send the same request if it has not received any response from a DNS server.
  Note: when a request is an RBL request, the Resolver sends the same request not more than twice, and both times it uses the same (Initial) response time-out.
`Source IP Address`
  This option selects the source network address and port for UDP DNR requests send. If an IP address and/or a port is not specified, the address and/or port is selected using the Server host OS.

The Domain Name Resolver uses TCP connections if a DNS server sent a UDP response with the "Truncated" flag set. This feature allows the Resolver to retrieve very large records from DNS servers.

Dummy IP Addresses
64.94.110.11 ; *.com, *.net "wildcard"

`Dummy IP Addresses`
  This Address List setting allows you to specify network (IP) addresses that should be considered as "non-existent".

  Some DNS authorities may choose to "map" all non-existent names within their domains to some special IP address(es).

  When a domain name is resolved into IP addresses, the Resolver checks the first address. If this address is listed in the Dummy IP Addresses list, the Resolver returns the "unknown host/domain name" error code.

The Domain Name Resolver caches responses to SRV-type DNS requests.

Cache
Limit: |  | Cache Negative: |

`Limit`
  The maximum Cache size. When the number of items in the cache exceeds this limit, the oldest unused records are being removed from the cache.
`Cache Negative`
  Use this setting to specify for how long negative (failure) DNS responses should be cached.

## IPv6 Support

The CommuniGate Pro Server provides full support for both IPv4 and IPv6 network protocols for the following Server Operating Systems:

- Linux
- FreeBSD
- MacOS X
- Windows (Vista and newer)
- Solaris
- NetBSD
- HP/UX
- AIX
- Tru64

If the Server runs on a platform with IPv6 support, and it detects any local IPv6 address, it assumes that the IPv6 networking is enabled.
In this case, the Server creates all network sockets as IPv6 sockets. These sockets communicate with IPv4 systems using the IPv4-mapped IPv6 address method.

Note: The IPv4-mapped IPv6 address method is disabled by default in FreeBSD and NetBSD system kernels. Use the

  `sysctl -w net.inet6.ip6.v6only=0`

command in your OS startup scripts to enable this method.

Note: The IPv4-mapped IPv6 address method is permanently disabled in OpenBSD system kernels. As a result, IPv6 networking is not supported on this platform.

You can explicitly instruct the Server to switch IPv6 networking support on or off by using the `--IPv6` Command Line Option:

- `--IPv6 NO` switches the IPv6 support off, even if some local IPv6 addresses are detected.
- `--IPv6 YES` switches the IPv6 support on, even if no local IPv6 local address is detected, but the Server OS supports IPv6 networking.

## Denied Addresses

You may want to deny access to your Server for all incoming TCP connections and UDP packets coming from certain IP Addresses.

Use the WebAdmin Interface to specify the Denied Addresses. Open the Network pages in the Settings realm, then open the Blacklisted IPs page.

Denied IP Addresses
10.18.0.0-10.18.255.255 172.16.3.2 192.168.0.0/16

The TCP and UDP Listeners consult with this IP Address list before they check their own restrictions settings.

In a Cluster environment, connections and packets from an IP Address are denied if that Address is included into either Server-wide or Cluster-wide Denied IP Addresses list.

## Debug Addresses

You may need to obtain a detailed Log of all communications with certain clients or remote servers.

Use the WebAdmin Interface to specify the Debug Addresses. Open the Network pages in the Settings realm, then open the Debug IPs page.

Debug IP Addresses
10.18.0.0-10.18.255.255 172.16.3.2 192.168.0.0/16

When the Server:

- accepts a TCP connection from an address in this list
- opens a TCP connection to an address in this list
- receives a UDP packet from an address in this list
- sends a UDP packet to an address in this list

the protocol Log Level for that connection or packet is set to All Info.

In a Cluster environment, both the Server-wide or Cluster-wide Debug Addresses lists are checked.

CommuniGate® Pro Guide. Copyright © 1998-2012, Stalker Software, Inc.