Kerio Tech KERIO WINROUTE FIREWALL 6 User Manual download pdf (Page 119)

8.3 Dynamic DNS for public IP address of the ﬁrewall

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Warning

1. DHCP server cannot assign addresses to RAS clients connecting to the RAS server

directly at the WinRoute host (for technical reasons, it is not possible to receive DHCP

queries from the local RAS server). For such cases, it is necessary to set assigning of

IP addresses in the RAS server conﬁguration.

2. The RAS service in Windows leases a new IP address for each connection (even if re-

quested by the same client). WinRoute includes RAS clients in total number of clients

when checking whether number of licensed users has been exceeded (see chapter 4.6).

This implies that repeated connection of RAS clients may cause exceeding of the num-

ber of licensed users (if the IP scope for the RAS service is too large or/and an address

is leased to RAS clients for too long time). Remote clients will be then allowed to con-

nect and communicate with hosts in the local network, while they will not be allowed

to connect to the Internet via WinRoute.

Declined options

These options deﬁne how declined IP addresses (DHCPDECLINE report) will be handled.

These addresses can be either considered released and assigned to other users if needed

(the Oﬀer immediately option) or blocked during a certain time for former clients to be

able to use them (the Declined addresses can be oﬀered after timeout option).

8.3 Dynamic DNS for public IP address of the ﬁrewall

Kerio WinRoute Firewall provides (among others) services for remote access from the Internet

to the local network (VPN server — see chapter 23 and the Clientless SSL-VPN interface — see

chapter 24). Also other services can be accessible from the Internet — e.g. the Kerio StaR

interface (see chapter 21), remote administration of WinRoute by the Administration Console

(see chapter 16.2) or any other service (e.g. web server in local network — see chapter 7.4).

These services are available at the ﬁrewall’s public IP address. If this IP address is static and

there exists a corresponding DNS record for it, a corresponding name can be used for access

to a given service (e.g. server.company.com). If there is no corresponding DNS record, it is

necessary to remember the ﬁrewall’s IP address and use it for access to all services. If the

public IP address is dynamic (i.e. it changes), it is extremely diﬃcult or even impossible to

connect to these services from the Internet.

This problem is solved by WinRoute’s support for dynamic DNS. Dynamic DNS provides DNS

record for a speciﬁc name of a server which will always keep the current IP address. This

method thus allows making mapped services always available under the same server name,

regardless of the fact if IP address changes and how often.

How cooperation with dynamic DNS works

Dynamic DNS (DDNS) is a service providing automatic update of IP address in DNS record for

the particular host name. Typically, two versions of DDNS are available:

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Kerio Tech KERIO WINROUTE FIREWALL 6 User Manual Page 119