vni(7d) [x11r4 man page]
vni(7d) Devices vni(7d) NAME
vni - STREAMS virtual network interface driver DESCRIPTION
The vni pseudo device is a multi-threaded, loadable, clonable, STREAMS pseudo-device supporting the connectionless Data Link Provider Interface dlpi(7P) Style 2. Note that DLPI is intended to interact with IP, meaning that DLPI access to applications is not supported. (For example, snoop fails on the vni interface.) The vni device is a software-only interface and does not send or receive data. The device provides a DLPI upper interface that identifies itself to IP with a private media type. It can be configured via ifconfig(1M) and can have IP addresses assigned to it, making aliases pos- sible. The vni pseudo device is particularly useful in hosting an IP address when used in conjunction with the 'usesrc' ifconfig option (see ifconfig(1M) for examples). The logical instances of the device can also be used to host addresses as an alternative to hosting them over the loopback interface. Multicast is not supported on this device. More specifically, the following options return an error when used with an address specified on vni: IP_MULTICAST_IF, IP_ADD_MEMBERSHIP, IP_DROP_MEMBERSHIP, IPV6_MULTICAST_IF, IPV6_JOIN_GROUP, IPV6_LEAVE_GROUP. In addition, broadcast is not supported. Because there is no physical hardware configured below it, no traffic can be received through nor transmitted on a virtual interface. All packet transmission and reception is accomplished with existing physical interfaces and tunnels. Because applications that deal with packet transmission and reception (such as packet filters) cannot filter traffic on virtual interfaces, you cannot set up a packet filter on a virtual interface. Instead, you should configure the policy rules to apply to the physical interfaces and tunnels, and if necessary, use the virtual IP addresses themselves as part of the rule configuration. Also, note that the virtual interface cannot be part of an IP multi- pathing (IPMP) group. FILES
/dev/vni 64-bit ELF kernel driver SEE ALSO
ifconfig(1M), in.mpathd(1M), ip(7P), ip6(7P) SunOS 5.10 18 July 2004 vni(7d)
Check Out this Related Man Page
CARP(4) BSD Kernel Interfaces Manual CARP(4) NAME
carp -- Common Address Redundancy Protocol SYNOPSIS
pseudo-device carp [count] DESCRIPTION
The carp interface is a pseudo-device which implements and controls the CARP protocol. carp allows multiple hosts on the same local network to share a set of IP addresses. Its primary purpose is to ensure that these addresses are always available, but in some configurations carp can also provide load balancing functionality. A carp interface can be created at runtime using the ifconfig carpN create command. To use carp, the administrator needs to configure at minimum a common virtual host ID and virtual host IP address on each machine which is to take part in the virtual group. Additional parameters can also be set on a per-interface basis: advbase and advskew, which are used to con- trol how frequently the host sends advertisements when it is the master for a virtual host, and pass which is used to authenticate carp advertisements. Finally carpdev is used to specify which interface the carp device attaches to. If unspecified, the kernel attempts to set carpdev by looking for another interface with the same subnet. These configurations can be done using ifconfig(8), or through the SIOCSVH ioctl. Additionally, there are a number of global parameters which can be set using sysctl(8): net.inet.carp.allow Accept incoming carp packets. Enabled by default. net.inet.carp.preempt Allow virtual hosts to preempt each other. It is also used to failover carp interfaces as a group. When the option is enabled and one of the carp enabled physical interfaces goes down, advskew is changed to 240 on all carp interfaces. See also the first example. Disabled by default. net.inet.carp.log Log bad carp packets. Disabled by default. net.inet.carp.arpbalance Balance local traffic using ARP. Disabled by default. EXAMPLES
For firewalls and routers with multiple interfaces, it is desirable to failover all of the carp interfaces together, when one of the physical interfaces goes down. This is achieved by the preempt option. Enable it on both host A and B: # sysctl -w net.inet.carp.preempt=1 Assume that host A is the preferred master and 192.168.1.x/24 is configured on one physical interface and 192.168.2.y/24 on another. This is the setup for host A: # ifconfig carp0 create # ifconfig carp0 vhid 1 pass mekmitasdigoat 192.168.1.1 netmask 255.255.255.0 # ifconfig carp1 create # ifconfig carp1 vhid 2 pass mekmitasdigoat 192.168.2.1/24 netmask 255.255.255.0 The setup for host B is identical, but it has a higher advskew: # ifconfig carp0 create # ifconfig carp0 vhid 1 advskew 100 pass mekmitasdigoat 192.168.1.1 netmask 255.255.255.0 # ifconfig carp1 create # ifconfig carp1 vhid 2 advskew 100 pass mekmitasdigoat 192.168.2.1 netmask 255.255.255.0 Because of the preempt option, when one of the physical interfaces of host A fails, advskew is adjusted to 240 on all its carp interfaces. This will cause host B to preempt on both interfaces instead of just the failed one. In order to set up an ARP balanced virtual host, it is necessary to configure one virtual host for each physical host which would respond to ARP requests and thus handle the traffic. In the following example, two virtual hosts are configured on two hosts to provide balancing and failover for the IP address 192.168.1.10. First the carp interfaces on Host A are configured. The advskew of 100 on the second virtual host means that its advertisements will be sent out slightly less frequently. # ifconfig carp0 create # ifconfig carp0 vhid 1 pass mekmitasdigoat 192.168.1.10 netmask 255.255.255.0 # ifconfig carp1 create # ifconfig carp1 vhid 2 advskew 100 pass mekmitasdigoat 192.168.1.10 netmask 255.255.255.0 The configuration for host B is identical, except the skew is on virtual host 1 rather than virtual host 2. # ifconfig carp0 create # ifconfig carp0 vhid 1 advskew 100 pass mekmitasdigoat 192.168.1.10 netmask 255.255.255.0 # ifconfig carp1 create # ifconfig carp1 vhid 2 pass mekmitasdigoat 192.168.1.10 netmask 255.255.255.0 Finally, the ARP balancing feature must be enabled on both hosts: # sysctl -w net.inet.carp.arpbalance=1 When the hosts receive an ARP request for 192.168.1.10, the source IP address of the request is used to compute which virtual host should answer the request. The host which is master of the selected virtual host will reply to the request, the other(s) will ignore it. This way, locally connected systems will receive different ARP replies and subsequent IP traffic will be balanced among the hosts. If one of the hosts fails, the other will take over the virtual MAC address, and begin answering ARP requests on its behalf. Note: ARP balancing only works on the local network segment. It cannot balance traffic that crosses a router, because the router itself will always be balanced to the same virtual host. SEE ALSO
netstat(1), sysctl(3), arp(4), arp(8), ifconfig(8), sysctl(8) HISTORY
The carp device first appeared in OpenBSD 3.5. BSD
October 16, 2003 BSD