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ifconfig(8) System Manager's Manual ifconfig(8) NAME ifconfig - Configures or displays network interface parameters SYNOPSIS /usr/sbin/ifconfig interface_id [address_family] [address[/bitmask] [dest_address]] [parameters] /usr/sbin/ifconfig -a The ifconfig command assigns and displays an address to a network in- terface, and configures network interface parameters. FLAGS Displays information about all interfaces that are configured on a sys- tem. DESCRIPTION You use the ifconfig command at boot time to define the network address of each interface. You can also use the ifconfig command at other times to display all interfaces that are configured on a system, to re- define the address of an interface, or to set other operating parame- ters. If you want to redefine the interface address or the netmask, use the netsetup command. Otherwise, any daemons currently running will use the old address and netmask, and will fail. The netsetup com- mand makes the necessary changes and restarts the network services. Any user can query the status of a network interface; only the supe- ruser can modify the configuration network interfaces. You specify an interface with the ifconfig interface_id syntax. (See your hardware documentation for information on obtaining an interface ID.) If you specify only an interface_id, the ifconfig program displays the current configuration for the specified network interface only. If a protocol family is specified by the address_family parameter, if- config reports only the configuration details specific to that protocol family. When changing an interface configuration, if the address family cannot be inferred from the address parameter, an address family, which may alter the interpretation of succeeding parameters, must be specified. This family is required because an interface can receive transmissions in different protocols, each of which may require a separate naming scheme. The address argument is the network address of the interface being con- figured. For the inet address family, the address argument is either a hostname or an Internet address in the standard dotted-decimal notation with or without the optional Classless Inter-Domain Routing (CIDR) bit- mask (/bitmask). If using the bitmask argument, do not use the netmask parameter. The destination address (dest_address) argument specifies the address of the correspondent on the remote end of a point-to-point link. Parameters Closes all TCP connections associated with a network address. Use this parameter when removing aliases or deleting network addresses. This prevents users from experiencing a hanging connection when the network address is deleted. Creates a set of redundant adapters (NetRAIN). The interface-id specified must represent adapters of the same type connected to the same LAN segment. The ifconfig interface-id parameter must be a NetRAIN virtual interface name of the form nrx, where x is the unit number (Valid unit numbers are 0-9. This limit can be ad- justed using the sysconfig command). If the NetRAIN virtual interface does not exist, it is created. Establishes an additional network ad- dress for this interface. This can be useful when changing network numbers and you want to continue to accept packets addressed to the old interface. If you do not specify a bitmask or netmask with the alias ad- dress, the default netmask is based on the alias address's net- work class. If you are using the optional bitmask argument, do not use the netmask argument. Removes the network address specified. This can be used either if you incorrectly specified an alias or if an alias is no longer needed. The -alias parameter functions in the same manner as the delete parameter. Establishes a range of additional network addresses for this interface. The range can be a comma-separated list or a hyphenated list, and is inclu- sive. You can also specify the optional CIDR bitmask (/bitmask) argument at the end of the list. Do not use a comma-separated list and a hyphenated list for a range. For example, the fol- lowing aliaslist command adds network addresses 40 through 50, inclusive, to subnets 18.240.32, 18.240.33, 18.240.34, 18.240.35, and 18.240.36: ifconfig aliaslist 18.240.32-36.40-50 The following aliaslist command specifies the netmask 255.255.252.0 in CIDR format to the previous example: ifconfig aliaslist 18.240.32-36.40-50/22 The following aliaslist command adds network addresses 40 through 50, inclusive, to subnets 18.240.32, 18.240.64, and 18.240.96: ifconfig aliaslist 18.240.32,64,96.40-50 The following aliaslist command is invalid because a comma-separated list and a hyphenated list are used to denote a range: ifconfig aliaslist 18.240.32.40-50,55,58 Removes a range of network addresses for this interface. This can be useful when deleting network numbers and you want to keep the primary interface address. The alias list rules are the same as for the aliaslist parameter. Enables the recep- tion of all multicast packets. Disables the reception of all multicast packets. Enables the use of the Address Resolution Protocol (ARP) in mapping between network-level addresses and link-level addresses. This parameter is on by default. Disables the use of the ARP. Use of this parameter is not recommended. See arp(8) for more information. Speci- fies the address to use to represent broadcasts to the network. The default broadcast address is the address with a host part consisting of all 1s (ones). Note that the computation of the host part is dependent on netmask (see the description of the netmask parameter). Enables driver-dependent debug code. This might turn on extra console error logging. (See your hardware documentation for further information.) Disables driver-dependent debug code. Removes the network address specified. This would be used if you incorrectly specified an alias, or if it was no longer needed. If you have incorrectly set an NS ad- dress having the side effect of specifying the host portion, removing all NS addresses will allow you to respecify the host portion. If no address is specified, all network addresses for the inter- face are deleted. Marks an interface as not working (down), which keeps the system from trying to transmit messages through that interface. If possible, the ifconfig command also resets the interface to disable reception of messages. Routes that use the interface, however, are not automatically disabled. Enables access filtering on the interface. Reads the /etc/ifaccess.conf file and constructs an interface access filter based on entries in the file. Interface access filtering provides a mechanism for detecting and preventing IP spoofing attacks. (See CERT Ad- visory CA-95:01). The source addresses of IP input packets are checked against access filter entries; packets receive the ac- tion associated with the first matching entry. The following actions are valid: permit, deny, or denylog; the final filter entry is a default permit all. See ifaccess.conf(4) for more in- formation. Disables access filtering on the interface. Speci- fies an Internet host willing to receive IP packets encapsulat- ing packets bound for a remote network. For a Network Systems (NS) case, an apparent point-to-point link is constructed, and the address specified will be taken as the NS address and net- work of the destination host. Alters the size of the maximum transfer unit (MTU) for messages that your system transmits. It might be necessary to reduce the MTU size so that bridges con- necting token rings can transfer frames without error. Sets the routing metric, or number of hops, for the interface to the value of number. The default value is 0 (zero) if number is not specified, indicating that both hosts are on the same network. The routing metric is used by the routed and gated daemons, with higher metrics indicating that the route is less favorable. En- able NetRAIN monitoring on this interface. If the monitoring code determines that the interface is not operational, a message is sent to the console and to a log file. Specifies how much of the address to reserve for subdividing networks into sub-net- works. This parameter can only be used with an address family of inet. Do not use this parameter if you are specifying the CIDR mask (/bitmask) with the address argument, alias parameter, or aliaslist parameter. The mask variable includes both the network part of the local address and the subnet part, which is taken from the host field of the address. The mask can be specified as a single hexadeci- mal number beginning with 0x, in the standard Internet dotted- decimal notation, or beginning with a name. The mask contains 1s (ones) for the bit positions in the 32-bit address that are reserved for the network and subnet parts, and 0s (zeros) for the bit positions that specify the host. The mask should contain at least the standard network portion. The default netmask is based on the address parameter's network class. Sets the number of attempts to determine whether a Ne- tRAIN interface is operational before performing a failover to another interface. The default value is 4 retries; this value can be adjusted using the sysconfig command. For ATM LAN Emulation (LANE), set integer to 5. Sets the Ne- tRAIN interface monitoring interval. The default value is 1 sec- ond. This value sets the time it takes to perform a test on an operational interface. Sets the time between NetRAIN interface tests if an interface is marked down. Interface operability tests are not run unless the interface UP flag is set. This timer represents the time between checking the UP flag for an interface. Once the UP flag is set, the interface resumes normal monitoring mode. The default value is 10 seconds. Sets the time between NetRAIN interface tests after this interface has failed. The default value is 5 seconds. An interface is marked as having failed after the interface test fails retry count times. Sets the time-out value for the NetRAIN interrupt service routine which monitors interfaces. The default value is 1000 (1 second) and can be adjusted using the sysconfig command. This value controls all other time-out values. Each time the NetRAIN inter- rupt service routine executes, it decrements the time-out count for each interface being monitored. When the time-out count reaches zero, an operational test is performed on the interface. This value sets the frequency which the routine monitoring in- terfaces runs. Sets the time between NetRAIN interface tests when the previous test has failed but it has not failed retry count times. The default value is 1 second. For ATM LAN Emulation (LANE) interfaces, set integer to 2. Sets the time between NetRAIN interface tests when the previous test succeeded. The default value is 3 seconds. Sets the interface into promiscuous mode. This directs the network interface to re- ceive all packets off the network, rather than just those pack- ets directed to the host. Disables the promiscuous mode of the interface. This is the default. Remove the interfaces attached to a NetRAIN interface. All of the interfaces have their default hardware addresses restored and the UP flag is cleared. The hardware address of the NetRAIN virtual interface is set to 00:00:00:00:00:00 and its UP flag is cleared. The NetRAIN vir- tual interface may be reconfigured using the add command. Sets the speed at which the token ring adapter transmits and receives on the token ring network to value. The value can be either 4 for a ring speed of 4Mbs or 16 for 16Mbs. The adapter speed must match the signal speed of the token ring. This parameter also determines the speed (regular or fast Ether- net) and half- or full-duplex mode operation on the tu interface when that interface is using the twisted-pair port as follows: tab(@); lfHB lfHB r l. _ Value@Configuration _ 10@10 Mbps Ethernet half-duplex 20@10 Mbps Ethernet full-duplex 100@100 Mbps Ethernet half-duplex 200@100 Mbps Ethernet full-du- plex _ After the interface is online, you can use the ifconfig up and down options to change the speed value dynamically. Stop adapter transmission with down and set the speed in the same command line. Then specify up without a speed value to restart the adapter. Force a NetRAIN interface to failover to another interface in the NetRAIN set. If the ifconfig interface-id spec- ified is the NetRAIN virtual interface, the next available in- terface in the set becomes active. If the ifconfig interface-id is a member of the NetRAIN set, the interface-id specified be- comes the active member. If the interface-id specified is not operational, the switch command has no effect. Requests the use of a trailer link-level encapsulation when sending messages. If a network interface supports trailers, the system will, when possible, encapsulate outgoing messages in a manner that mini- mizes the number of memory-memory copy operations performed by the receiver. On networks that support the Address Resolution Protocol (see arp), this flag indicates that the system should request that other systems use trailers when sending to this host. Similarly, trailer encapsulations will be sent to other hosts that have made such requests. Currently used by Internet protocols only. Disables the use of a trailer link-level encap- sulation. This is the default. Sets the trust group identifier for the interface. Trust group identifiers are passed from the kernel to the screend daemon, and indicate the color of the in- terface on which a packet was received and the color of the in- terface to which a packet is intended, as indicated by the ker- nel routing tables. The group can be one of the primary colors in the visible spectrum (for example, red, orange, yellow, green, blue, indigo, and violet). The screend daemon can op- tionally use trust group information to make packet screening decisions. Marks an interface as working (up). This parameter is used automatically when setting the first address for an in- terface, or can be used to enable an interface after an ifconfig down command. If the interface was reset when previously marked with the parameter down (see the following section for a de- scription of this parameter), the hardware will be reinitial- ized. EXAMPLES To query the status of serial line interface sl0, enter: $ ifconfig sl0 sl0: flags=10<POINTOPOINT> To configure the local loopback inter- face, enter: # ifconfig lo0 inet 127.0.0.1 up Only a user with supe- ruser authority can modify the configuration of a network interface. To configure a ln0 interface, enter: # ifconfig ln0 212.232.32.1/22 The broadcast address is 212.232.35.255 as the 22-bit mask specifies four Class C networks. To configure the token ring interface for a 4 Mbps token ring with a netmask of 255.255.255.0 in CIDR format, enter: # ifconfig tra0 130.180.4.1/24 speed 4 To stop the token ring inter- face and start it for a 16 Mbps token ring, enter: # ifconfig tra0 down # ifconfig tra0 speed 16 up To create a NetRAIN set nr1 with the Ethernet interfaces tu0 and tu2 as the set members, enter: # ifconfig nr1 add tu0,tu2 To set the IP address of this interface to 18.240.32.40, enter: # ifconfig nr1 inet 18.240.32.40 To view this set, enter: # ifconfig nr1 nr1: flags=c63<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST,SIMPLEX> NetRAIN Attached Interfaces: ( tu0 tu2 ) Active Interface: ( tu0 ) inet 18.240.32.40 netmask ffffff00 broadcast 18.240.32.255 ipmtu 1500 To remove the interfaces tu0 and tu2 from the NetRAIN set created in the previous example, enter: # ifconfig nr1 re- move To stop Ethernet interface tu0, delete all addresses asso- ciated with the interface, and close all TCP connections, enter: # ifconfig tu0 down delete abort 145.92.16.1: aborting 7 tcp connection(s) To delete the alias address 145.92.16.2 on inter- face tu0 and close all TCP connections, enter: # ifconfig tu0 -alias 145.92.16.2 abort 145.92.16.2: aborting 2 tcp connec- tion(s) DIAGNOSTICS The bitmask specified is not in the range of 1 to 32, inclusive. The -netmask option was specified together with a CIDR bitmask. FILES Specifies the command path Interface access filtering configuration file. RELATED INFORMATION Commands: netstat(1), nr(7), inet.local(8), pfconfig(8). Daemons: gated(8), routed(8) screend(8). Files: ifaccess.conf(4). delim off ifconfig(8)