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HELIOS PCShare UB User manual |
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Each Windows client on the network needs a unique IP address, and there are three ways to get this address:
- Statically configured from " /etc/hosts" and " /etc/ethers" on the PCShare DHCP server
- Statically configured from " /etc/bootptab" on the PCShare DHCP server
- Dynamically configured on the PCShare DHCP server
The DHCP tab in the Server Settings menu is used to configure a PCShare DHCP server. The DHCP server allocates IP addresses dynamically, i.e.automatically. This avoids configuring each client individually with a manually assigned IP address. You need to configure a DHCP server if you want to use static or dynamic IP address allocation.
- IP address
- Subnet mask
- Gateway (Router) address, (if configured - see Fig. 11)
- DNS server address (if configured) in " /etc/resolv.conf"
- Domain name
- Server address
- Log server address
- Time server address
- NetBIOS scope
- WINS server address (if configured)
The DHCP tab shows details on the interface name and address, the subnet mask, the gateway to be used by a DHCP client, and details of a boot server (if existing) configuration (Fig. 11).
First choose Primary from the DHCP Server pull-down menu. Then assign a range of IP addresses to be set aside for dynamic allocation. To do this click the Add- button and fill in the IP address range.
You can assign several ranges if needed, but make sure they do not overlap. You may also choose another host interface and assign a range on that, too. The range you specify is checked for plausibility, and if the range spans the host interface itself, it will be split automatically into two ranges.
In " HELIOSDIR/var/conf/ethers.pcs" the server stores the client workstation name, the Ethernet address, and the date of usage in order to assign the same IP address on the next DHCP request.
If your network has more than one PCShare server, you may optionally configure a backup DHCP server, to guarantee network availability if the main PCShare DHCP server is down for any reason. The secondary DHCP server automatically adopts the configuration file " ethers.pcs" from the primary DHCP server. In case the primary DHCP server is down for more than 2 seconds, the secondary DHCP server assumes the DHCP service. As soon as the primary DHCP server is available again, it takes over DHCP service.
Start HELIOS Admin on the host you wish to configure as secondary DHCP server. This is because the secondary DHCP server configuration file must be stored on the secondary host and not on the primary.
Choose Secondary from the DHCP Server pull-down menu and enter the name of the primary DHCP server in the Primary Server field.
Fig. 12 shows the secondary DHCP server " blade" configured as a backup for the primary DHCP server " ankh" .
Select a host interface and choose Disabled from the DHCP Server pull-down menu to disable the servicing of client boot requests on the specified interface. It is recommended to do this if your DHCP server has more than one interface, and one of them should not be used.
Note: If your network has two or more hosts, which are also DHCP server and use NIS, we recommend that you disable servicing of boot requests on the interfaces of all other hosts. Otherwise, all hosts will answer boot requests for clients which are configured statically in
" /var/yp/hosts" and " /var/yp/ethers" (or equivalent).Note: See also 5.3 "Configuring IP address and host name for PCShare clients".
This feature requires a DNS server with bind version 8 or newer and on the PCShare server a bind 8 compatible DNS client installation, and the " nsupdate" (or similar) application. Most OS vendors provide a bind of version 8 or newer with their current OS implementation, apart from HP-UX 11 and IRIX 6.5. Check with your hardware/operating system vendor for OS requirements and availability of bind 8.
With the above requirements met, PCShare supports dynamic DNS update according to RFC 2136 and secure DNS according to RFC 2137.
Note: Bind 8 prior to 8.2 includes support for dynamic DNS as specified in RFC 2136 but it does not currently include the authentication mechanism described in RFC 2137. As a result, any update requests received from allowed hosts will be accepted.
A DHCP TCP/IP address range for PCShare can be specified in the DHCP tab in the HELIOS Admin Server Settings dialog (Fig. 13). The DHCP clients will receive this TCP/IP configuration including IP address, subnet mask, router, WINS and DNS server address. This enables the client to be a fully configured TCP/IP citizen, to connect to the server and use other TCP/IP services like web browser, etc.
A standard ping on the DHCP client shows that the DHCP client is alive (e.g. ping 172.16.0.123). A reverse lookup e.g.: (ping mac-mike.helios.de) will only work if the client TCP/IP address has an entry in the DNS server configuration. PCShare can automatically update the DNS server with the host names of DHCP clients. The benefit of this is that the DNS configuration gets dynamically updated every time PCShare provides a DHCP configuration to a client (e.g. Macintosh or Windows clients).
It is required to specify the DNS domain in which the DHCP name should be configured (e.g. " helios.de" ). The DHCP client name will be used for the DNS configuration. A sample DNS reverse lookup would be e.g.:
Note: To avoid a simple DHCP client from overwriting your DNS configuration by setting the client workstation name e.g. to " ftp" , which means it will update the DNS setting of " ftp.helios.de" to the client IP address, we recommend to specify a unique domain for dynamic DNS clients. In our example we configure the PCShare dynamic DNS update name to " dyn.helios.de" which would register the client as " mac-mike.dyn.helios.de" .
The DNS server can run on the same machine as PCShare, or on a different server on the network. By default, the DNS server will deny all remote DNS updates for security reasons. It is required to allow the DNS server to accept remote updates which are initiated by the PCShare DHCP server.
Using a UNIX based DNS server the " /etc/named.conf" configuration file needs an entry like the following to allow the PCShare server to update DNS entries. Let us assume our PCShare DHCP server has the IP address " 172.16.0.1" :
zone "dyn.helios.de" {
type master;
file "heliosdyn.data";
allow-update { localhost; 172.16.0.1; };
};
On Windows and Macintosh clients the DHCP request contains the workstation name, which is used to register the DNS workstation name, (e.g. " mac-mike" which will be " mac-mike.dyn.helios.de" ).
On Mac OS X the computer name is configured in the Computer Name field, in the system preferences Sharing section (Fig. 14). On Mac OS 9 workstations specify the computer name in the File Sharing control panel in the Computer Name field.
On Windows computers the workstation name is configured in System Properties > Computer name (Fig. 15).
Please note: If two DHCP clients are using the same name only the last DNS entry will be valid. There is no warning or error message for duplicate names. To allow successful dynamic DNS updates the workstation name should only contain digits 0-9 and ASCII characters. Special characters like umlauts, spaces, underlines, etc. may not work correctly.
The PCShare DHCP configuration file
" HELIOSDIR/var/conf/ethers.pcs" will contain a list of the assigned Mac address and TCP/IP address including the workstation names, e.g.:
When using a primary and secondary PCShare DHCP server, make sure that the bind requirements for dynamic DNS, which have been described before in 5.2.1 "PCShare DHCP with dynamic DNS update", are also available on the secondary DHCP server. Otherwise it will not be able to update dynamic DNS.
In TCP/IP networks it is essential to have a unique IP address for each TCP/IP node on the network. Thus each PCShare client needs a unique address. If the network is connected externally to the Internet, each IP address must be unique worldwide too, and must be assigned by the appropriate regulatory authority.
Furthermore, in the case of Ethernet, each network card has a hardware address which must be unique for each local network segment. This is taken care of automatically, usually by the network card manufacturer.
It is common to give each TCP/IP node a name, too (the name is easier to remember than the IP address). Information on host name, IP address and Ethernet address of each service is typically stored in the following UNIX system files.
- " /etc/ethers" (or the equivalent NIS or the " bootptab" file) specifies the network hardware address and host name (or IP address).
- " /etc/hosts" (or the equivalent NIS or domain name resolver) specifies the IP address and host name.
Important: If you modify entries in the files " ethers.pcs" or " bootptab" manually, you must run the command srvutil reconf pcshare. Otherwise the changes will not be recognized by the server!
Each PC client in the PCShare network needs a unique IP address, and there are three ways - apart from local configuration - that it can get this:
Client IP addresses are allocated by manually editing the appropriate UNIX system files (" /etc/ethers" and " /etc/hosts" or their NIS equivalent). See your UNIX documentation for details.
Client IP addresses are allocated by manually editing the appropriate UNIX system files (" /etc/bootptab" and " /etc/hosts" or their NIS equivalent). See your UNIX documentation for details.
Client IP addresses are allocated by the " pcshare" server and stored in " HELIOSDIR/var/conf/ethers.pcs" on the host. This method, called dynamic address allocation, is less work for the system administrator, especially in large networks.
Method c) requires you to configure a " PCShare DHCP server" on your PCShare host. Configuration is best done in the DHCP tab in HELIOS Admin Server Settings menu.
It is also possible to use a combination of all three methods on the same network. The PCShare client sends a " boot" request to hosts on the same network segment to get an IP address. If a PCShare server receives this boot request, and if it is configured as a DHCP server, it first checks the appropriate UNIX system files for the PC's IP address, and then looks for an entry in " HELIOSDIR/var/conf/ethers.pcs" . An address is assigned automatically if its Ethernet address is not already listed in either of these two places. The assigned address is then appended as a new entry in the " ethers.pcs" file to make sure that the client gets the same address in the future, too.
Important: Make sure not to use overlapping IP ranges, e.g. when using a combination of all three methods because this would lead to severe IP address allocation malfunctions!
" ethers.pcs" documents the relationship between network hardware address and IP address for dynamically assigned client IP address, together with the date of last change for each entry. It is updated by the " pcshare" server program automatically - whenever a client connects to the server for the first time, it is assigned a new unique IP address if it does not already have one in this file (or by methods a), or b) in " /etc/hosts" , " /etc/ethers" and " /etc/bootptab" ).
" ethers.pcs" also contains information on a range of IP addresses which have been set aside by the system administrator for dynamic allocation.
Furthermore, a mechanism is provided to age entries which have not been used for a specified period of time, i.e. to delete them from this file automatically. For example, aging will occur if the PC is no longer used for server access, or if you initially allow the PC's IP address to be assigned dynamically, and then add an entry for the PC to the standard host system files. For more details, see the preference dynage in 6.1 "PCShare preferences".
If you delete client entries from " ethers.pcs" manually, dynamically-configured clients will be assigned a new IP address automatically, but it probably will be different to the one before.
Primary: 192.9.201.33-192.9.201.39
Primary: 192.9.201.41-192.9.201.44
#
#ethernet addr. internet addr. last change date
#
2:60:8c:2:ad:6c 192.9.201.36 Sat Feb 19 18:20:51
0:0:6b:81:39:12 192.9.201.37 Fri Nov 12 15:00:33
9:0:7:ff:ff:ff 193.9.201.43 Fri Nov 12 15:00:33
.
.
In this example, two ranges of IP addresses have been set aside by the system administrator for dynamic allocation. If the PCShare server has more than one network interface, the interfaces to be used for servicing client boot requests are determined automatically from the specified range(s).
You should list all gateways (if there is more than one) on your network with the gateways preference, or just use HELIOS Admin to configure the gateways.
" pcsaddr" can be used on a primary PCShare DHCP server to update the " ethers.pcs" file on-the-fly. A secondary PCShare DHCP server will learn changed information from the primary DHCP server as described in Primary and secondary DHCP servers below.
Adds a combination of IP address <addr> and client hardware address <macaddr> so that next time the client with hardware address <macaddr> will receive the IP address <addr> when booting.
Sets the <hostname> for IP address <addr> so that next time the client which receives IP address <addr> during boot up will also receive a resolvable host name. The IP address must already be available to the PCShare master process, e.g. either listed in " HELIOSDIR/var/conf/ethers.pcs" or added before, by using pcsaddr -a. <hostname> must only contain digits 0-9, and characters a-z, A-Z.
Note: " pcsaddr" will only do rudimentary consistency checks, so given addresses or names must comply with the DHCP specifications.
If your network has more than one PCShare server, you can optionally configure an additional " secondary DHCP server" as a backup to guarantee network availability if the main PCShare server is down for any reason. Configuration is best done with HELIOS Admin (DHCP tab in Settings > Server Settings).
The syntax of " HELIOSDIR/var/conf/ethers.pcs" is slightly different for secondary DHCP servers. The following is an example of " ethers.pcs" for a secondary DHCP server:
Secondary: 192.9.201.32 helios
Disabled: 192.9.201.50
#
#ethernet addr. internet addr. last change date
#
2:60:8c:2:ad:6c 192.9.201.36 Sat Feb 19 18:20:51
0:0:6b:81:39:12 192.9.201.37 Fri Nov 12 15:00:33
9:0:7:ff:ff:ff 193.9.201.43 Fri Nov 12 15:00:33
Specifying Secondary as DHCP server state allows PCShare to become a backup DHCP server. You then will be asked to enter the IP address of the primary DHCP server, which is needed to keep in sync with the current list of DHCP clients. The secondary DHCP server then gets the rest of the required configuration information automatically from the primary DHCP server. For this to take place, the secondary and primary DHCP server must both be running simultaneously at least once while a dynamically-configured client tries to boot.
The Disabled entry disables the servicing of client boot requests on the specified interface. Do this to disable the servicing of boot requests on the network segment if there is already another DHCP server.
Note: If your network uses NIS, and has two or more hosts which are also DHCP servers, we recommend that you use the Disabled option to disable servicing of boot requests on the interfaces of all other hosts. Else, all hosts will answer boot requests for clients which are configured statically in " /var/yp/hosts" and
" /var/yp/ethers" (or equivalent).
| © 2005 HELIOS Software GmbH |
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