Linux/Networking Services - Revision history

Admin: /* Overview */

2016-03-14T23:23:20Z

Overview

← Older revision		Revision as of 23:23, 14 March 2016
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	This page will cover a couple of key aspects of networking services on Linux:		This page will cover a couple of key aspects of networking services on Linux:
	* ip address schema		* ip address schema - [[Linux/IP Schema]]
	* dhcp server		* dhcp server - [[Linux/DHCP]]
	* dns server		* dns server - [[Linux/DNS]]
	* ntp server		* ntp server - [[Linux/NTP]]


	=Related=		=Related=

	{{LinuxNetworkingFlag}}		{{LinuxNetworkingFlag}}

Admin: /* DNS Server */

2016-03-14T23:22:59Z

DNS Server

Show changes

Admin: /* dhcp server */

2016-03-14T23:10:45Z

dhcp server

← Older revision		Revision as of 23:10, 14 March 2016
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	* dns server		* dns server
	* ntp server		* ntp server


	~~==dhcp server==~~

	~~now that we have used ipcalc to decide on a network layout (ip schema, number of addresses, number of bits, subnet mask, etc.), put it into action.~~

	~~set up dhcp server to configure and serve up IPv4 addresses to machines that want one.~~

	~~Use the <code>isc-dhcp-server</code>:~~

	~~<pre>~~
	~~$ apt-get install isc-dhcp-server~~
	~~</pre>~~

	~~Now configure the dhcp server by editing its configuration file, located at <code>/etc/dhcp/dhcp.conf</code>~~

	~~If you have a sample dhcp.conf file present, it will be pretty extensive. Or, it might be totally empty. Here is a sample:~~

	~~<pre>~~
	~~default-lease-time 86400;~~
	~~max-lease-time 86400;~~
	~~option subnet-mask 255.255.252.0;~~
	~~option broadcast-address 10.10.99.255;~~
	~~option domain-name "local.lan";~~
	~~authoritative;~~
	~~subnet 10.10.96.0 netmask 255.255.252.0 {~~
	~~range 10.10.99.100 10.10.99.254;~~
	~~option routers 10.10.96.1;~~
	~~option domain-name-servers 10.10.96.1;~~
	}

	~~</pre>~~

	~~To go through that a bit slower:~~

	~~the default lease time and max lease time set the lease times of ip addresses.~~

	~~The subnet mask and broadcast address options specify what subnet mask the clients will be given, and what broadcast address they'll use.~~

	The subnet mask identifies the network that each connecting node will be a part of. The clients check their IP information after being provided an address. The subnet mask identified here should be shown.

	~~The broadcast address is the address on which all nodes within this subnet are able to receive packets.~~

	The domain-name option applies the domain name to the hostnames of each node that connects to the DHCP server. The authoritative option specifies that this DHCP server should be the primary DHCP server for this subnet.

	~~The following lines about the subnet range, routers, and domain name servers:~~

	~~<pre>~~
	~~subnet 10.10.96.0 netmask 255.255.252.0 {~~
	~~range 10.10.99.1 10.10.99.254;~~
	~~option routers 10.10.96.1;~~
	~~option domain-name-servers 10.10.96.1;~~
	}
	~~</pre>~~

	~~these identify network address for the subnet, the subnet mask, the range of IP addresses that will be issued, the default gateway, and the DNS server.~~

	~~This example shows that the first DHCP-issued address will be at 10.10.99.100 and it will end at 10.10.99.254.~~

	~~This cuts out a really large number of possible IP addresses. The range we have specified, <code>10.10.96.0/22</code>, covers the following subnets:~~

	~~<pre>~~
	~~10.10.96.0~~
	~~10.10.97.0~~
	~~10.10.98.0~~
	~~10.10.99.0~~
	~~</pre>~~

	~~so in fact we could hand out IP addresses starting at <code>10.10.96.1</code>, rather than <code>10.10.99.100</code>.~~

	~~Once you have edited this file, you will restart the daemon.~~

	~~<pre>~~
	~~$ systemctl restart isc-dhcp-server~~
	~~</pre>~~

	~~===an easier example===~~

	~~This example is easier, as it only configures a network like <code>10.10.10.0/24</code> - a 24 bit network:~~

	~~<pre>~~
	~~default-lease-time 86400;~~
	~~max-lease-time 86400;~~
	~~option subnet-mask 255.255.255.0;~~
	~~option broadcast-address 10.10.10.255;~~
	~~option domain-name "local.lan";~~
	~~authoritative;~~
	~~subnet 10.10.10.0 netmask 255.255.255.0 {~~
	~~range 10.10.10.10 10.10.10.254;~~
	~~option routers 10.10.96.1;~~
	~~option domain-name-servers 10.10.96.1;~~
	}
	~~</pre>~~

	This sets the dhcp range to start at <code>10.10.10.10</code> and end at <code>10.10.10.254</code>. This gives 9 IP addresses that will never be assigned - which is useful if you need to assign static IP addresses to any machines.

	~~===Static IP Addresses===~~

	~~To configure the DHCP server to hand out a static IP address lease, place a reservation at the end of <code>/etc/dhcp/dhcpd.conf</code>:~~

	~~<pre>~~
	~~host miami {~~
	~~hardware ethernet AA:BB:AB:BA:DE:AD:BE:EF~~
	~~fixed-address 10.10.97.4~~
	}
	~~</pre>~~

	~~This will give the host miami with the mac address specified the fixed IP address of 10.10.97.4.~~

	~~===Restarting DHCP Server===~~

	~~To restart the DHCP server once you have made changes:~~

	~~<pre>~~
	~~$ systemctl restart isc-dhcp-server~~
	~~</pre>~~

Admin: /* IP Schema */

2016-03-14T23:05:02Z

IP Schema

← Older revision		Revision as of 23:05, 14 March 2016
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	* dns server		* dns server
	* ntp server		* ntp server


	~~==IP Schema==~~

	~~First principle: keep schema easy to change~~

	What types of machines are you providing addresses to? Servers/workstations/printers, but now also phones, conference systems, tablets. many devices also have multiple network interfaces. a default network of 24 bits, 254 usable ip addresses, is not large enough for many situations.

	~~multiple subnets would help to create individual networks for groups of devices (types of services). example: have servers on one subnet, printers on antoher, workstations on yet another.~~

	the broadcast domain should also be limited. With a one-size-fits-all 24 bit network, you have a single subnet, and a single broadcast domain. Every device can communicate with every other device, with no need for routing. However, on large networks, breaking down the broadcast domain can help ensure performance. Organizing sub domains for different services keep those services from being overwhelmed.

	~~To plan IP schema, use the <code>ipcalc</code> utility. This can help you understand the number of IP addresses that will be available for a given schema.~~

	~~<pre>~~
	~~$ apt-get install ipcalc~~
	~~</pre>~~

	~~You give it arguments of the network you are thinking about using:~~

	~~<pre>~~
	~~$ ipcalc 10.10.96.0/22~~
	~~</pre>~~

	~~ipcalc shows Hosts/Net, which is the number of allowable IP addresses that this network would give us.~~

	~~The utility also shows the subnet mask that would be required, which is <code>255.255.252.0</code>.~~

	~~===ipv4 vs ipv6===~~

	~~insert obligatory reference to number of IP addresses running out...~~

	~~ipv6 needs to be ushered in.~~

	HOWEVER, for small, internal networks, there is absolutely no need to complicate your life with ipv6. The namespace for ipv4 running out will only affect the wider internet, and not local nor private network IP spaces.

	~~Unless you are a networking company. Or studying for a certification.~~

Admin: /* Local DNS Configuration */

2016-03-14T23:00:04Z

Local DNS Configuration

← Older revision		Revision as of 23:00, 14 March 2016
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	===Local DNS Configuration===		===Local DNS Configuration===

	Now we can set up the configuration for ~~our~~ local network in the ~~other configuration file. Edit this~~ file:		Now we can set up the DNS configuration for the local network and its subnets. Start by editing the file:

	<pre>		<pre>
Line 246:		Line 246:
	</pre>		</pre>

	~~Now add~~ the following contents:		Add the following contents to that file:

	<pre>		<pre>
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	* This block calls out another file, "/etc/bind/net.local.lan"		* This block calls out another file, "/etc/bind/net.local.lan"
	* The remaining four blocks create configurations for reverse lookups on the four subnets we are creating. If you only have one subnet on your network, you will only include one block for the one subnet.		* The remaining four blocks create configurations for reverse lookups on the four subnets we are creating. If you only have one subnet on your network, you will only include one block for the one subnet.
	* Each subnet has its own reverse-lookup file where we can configure things~~, each being~~ stored in <code>/etc/bind</code>.		* Each subnet has its own reverse-lookup file where we can configure things. Each file is stored in <code>/etc/bind</code>.

	===DNS Records===		===DNS Records===

Admin: /* Configure DNS Forwarding */

2016-03-14T22:58:23Z

Configure DNS Forwarding

← Older revision		Revision as of 22:58, 14 March 2016
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	===Configure DNS Forwarding===		===Configure DNS Forwarding===

	~~We will start~~ by editing the BIND configuration options:		Start by setting up your DNS server to forward DNS requests that it can't handle to another (public) DNS server. Start by editing the BIND configuration options:

	<pre>		<pre>

Admin: /* Configurin gDNS */

2016-03-14T22:57:49Z

Configurin gDNS

← Older revision		Revision as of 22:57, 14 March 2016
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	Until the DNS server is configured, it won't be doing anything for us.		Until the DNS server is configured, it won't be doing anything for us.

	===~~Configurin gDNS~~===		===Configuring DNS===

	The configuration file for BIND is located in <code>/etc/bind/named.conf</code>.		The configuration file for BIND is located in <code>/etc/bind/named.conf</code>.

Admin: /* DNS Records */

2016-03-14T22:16:29Z

DNS Records

@@ Line 314: / Line 314: @@
 * SOA is start of authority, which defines which comptuer has DNS authority on this local network. The <code>administrator.local.lan</code> is an email address.
 * 201507261 is the serial number. if you change a zone file in bind, you should change this serial number. It is the first thing the daemon reads and it is how the daemon knows if the DNS records have been changed.
 =Related=
 {{LinuxNetworkingFlag}}

Admin: /* DNS Records */

2016-03-14T22:15:59Z

DNS Records

← Older revision		Revision as of 22:15, 14 March 2016
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	$TTL 1D		$TTL 1D

	@ IN SOA local.lan. ~~hostmaster~~.local.lan. (		@ IN SOA local.lan. administrator.local.lan. (

	201507261 ; serial		201507261 ; serial
Line 305:		Line 305:
	hermes IN A 10.10.96.1		hermes IN A 10.10.96.1
	puppet CNAME galaxy		puppet CNAME galaxy
	;		;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
	; dns zone for for local.lan		; end dns zone for for local.lan network
	;		;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
	</pre>		</pre>

			Going through this line by line:
			* TTL is time to live, set to 1 day - this is how long DNS records are cached (important with multiple DNS servers or dynamic IP addresses)
			* SOA is start of authority, which defines which comptuer has DNS authority on this local network. The <code>administrator.local.lan</code> is an email address.
			* 201507261 is the serial number. if you change a zone file in bind, you should change this serial number. It is the first thing the daemon reads and it is how the daemon knows if the DNS records have been changed.

	=Related=		=Related=

	{{LinuxNetworkingFlag}}		{{LinuxNetworkingFlag}}

Admin: /* DNS Records */

2016-03-14T22:12:41Z

DNS Records

@@ Line 281: / Line 281: @@
 Starting with <code>/etc/bind/net.local.lan</code>:
 =Related=
 {{LinuxNetworkingFlag}}