For each interface, it attempts to configure the interface using the DHCP protocol. In order to keep track of leases across system reboots and server restarts, dhclient keeps a list of leases it has been assigned in the dhclient. On startup, after reading the dhclient. When a new lease is acquired, it is appended to the end of the dhclient.
In order to prevent the file from becoming arbitrarily large, from time to time dhclient creates a new dhclient. The old version of the dhclient.
Old leases are kept around in case the DHCP server is unavailable when dhclient is first invoked generally during the initial system boot process. In that event, old leases from the dhclient. A mobile host which may sometimes need to access a network on which no DHCP server exists may be preloaded with a lease for a fixed address on that network.
When all attempts to contact a DHCP server have failed, dhclient will try to validate the static lease, and if it succeeds, will use that lease until it is restarted. In that case, it may be advantageous to arrange with the network administrator for an entry on the BOOTP database, so that the host can boot quickly on that network rather than cycling through the list of old leases.
The names of the network interfaces that dhclient should attempt to configure may be specified on the command line. If no interface names are specified on the command line dhclient will normally identify all network interfaces, eliminating non-broadcast interfaces if possible, and attempt to configure each interface. It is also possible to specify interfaces by name in the dhclient.
If interfaces are specified in this way, then the client will only configure interfaces that are either specified in the configuration file or on the command line, and will ignore all other interfaces. The client normally prints no output during its startup sequence. It can be made to emit verbose messages displaying the startup sequence events until it has acquired an address by supplying the -v command line argument.
In either case, the client logs messages using the syslog 3 facility. Note well: enabling this may prevent the client from using any leases it receives if the servers aren't configured to supply all of the items. Modifying default file locations: The following options can be used to modify the locations a client uses for its files.
During operations the client may use multiple UDP ports to provide different functions. Which ports are opened depends on both the way you compiled your code and the configuration you supply.
The following should provide you an idea of what ports may be in use. It also opens a fallback UDP socket for use in sending unicast packets.
Unlike DHCPv4 the well known socket doesn't need to be opened in raw mode. If you have included an omapi port statement in your configuration file then the client will open a TCP socket on that port to listen for OMPAI connections. After launching: Choose a connection from the Wired or Wireless tab and click Edit. The setting you want is supersede domain-name-servers See the dhclient. Bridging Bridging puts multiple interfaces into the same network segment. This is very popular when connecting a server to multiple switches for high availability or with virtualization.
In the latter case it is usually used to create a bridge in the host eg. The bridge-utils package is required to create bridged interfaces. Example: Connect a server to 2 switches via eth0 and eth1 by defining bridge 0 and give the server an IP address in this subnet: auto br0 iface br0 inet static address Therefore STP must be turned on via an "up" command as shown above.
Example: Bridge setup without IP address configuration use "manual" instead of "static" to "forward" an interface to a guest VM. The static bridge config contains only 1 physical interface. The virtual interface will be added to the bridge when the VM is started. This is usually fine with Cisco Switches, but eg.
Juniper switches use the RSTP costs and therefore this may lead to different spanning tree calculations and loop problems. This can be fixed by settings the costs manually, either on the switch or on the server. Bridging without Switching By default the Linux bridge acts like a switch.
This means, it remembers the MAC addresses behind a switch port and if the destination MAC address is known, data packets or only forward to the respective port - otherwise packets will be broadcasted. In some setups this is bad. For example if the bridge connects 2 trunk interfaces and the same MAC addresses may be seen from both interfaces, depending on the VLAN.
YYY, then there is no need to specify the vlan-raw-device, as the raw device can be retrieved from the interface name. Eg: auto eth0. Just config the bridge, and the VLAN interface will be created automatically when creating the bridge, e.
Attaching the physical interface eth0 to a bridge eg. Kernel newer than 2. This is done using a post-up line in the bonding interface configuration.
This is useful when more than one server is to be visible via the Internet. Note that virtual hosts can support multiple Apache servers with a single IP address. Take 0 off.
Also you should reverse the ordering of domain-name-servers. Clients will ask the first server in the list first. If your router acts as a name server as well it is most likely to remember previous queries for some time. This means if your Clients request the same address a second time the answer is much quicker, compared to asking a google name server. Skip to content configuration debian router I'm trying to setup Debian Squeeze ala Dreamplug as a router.
See systemd-networkd 8. The flow of this resolution is the following. The files method is invoked first. The dns method is invoked.
Each line starts with a IP address and it is followed by the associated hostname. The IP address The Debian Installer creates this entry for a system without a permanent IP address as a workaround for some software e. For a system with a permanent IP address, that permanent IP address should be used here instead of If installed, it is a symbolic link.
Either way, it contains information that initialize the resolver routines. Host names ending with the ". Modern Windows system usually use the dns method for the hostname resolution. Watch out for the name collision when chosing a domain name used only within LAN. The systemd uses " Predictable Network Interface Names " such as " enp0s25 ". Let us be reminded of the IPv4 32 bit address ranges in each class reserved for use on the local area networks LANs by rfc These addresses are guaranteed not to conflict with any addresses on the Internet proper.
IP address written with colon are IPv6 address , e. If one of these addresses is assigned to a host, then that host must not access the Internet directly but must access it through a gateway that acts as a proxy for individual services or else does Network Address Translation NAT. Although most hardware devices are supported by the Debian system, there are some network devices which require DFSG non-free firmware to support them. Please see Section 9. Network interfaces are typically initialized in " networking.
Debian can manage the network connection via management daemon software such as NetworkManager NM network-manager and associated packages. They come with their own GUI and command-line programs as their user interfaces. They come with their own daemon as their backend system.
They allow us to configure network independent of the legacy ifupdown package. Do not use these automatic network configuration tools for servers. These are aimed primarily for mobile desktop users on laptops. Debian ".
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