| arp.4 (23717fc46a574b84f6dabff1ddb211d255ea8437) | arp.4 (1a5d3a92f2c7bade925679817946f53d4d01ff9b) |
|---|---|
| 1.\" Copyright (c) 1985, 1986, 1988, 1994 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. --- 14 unchanged lines hidden (view full) --- 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)arp4.4 6.5 (Berkeley) 4/18/94 29.\" $FreeBSD$ 30.\" | 1.\" Copyright (c) 1985, 1986, 1988, 1994 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. --- 14 unchanged lines hidden (view full) --- 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)arp4.4 6.5 (Berkeley) 4/18/94 29.\" $FreeBSD$ 30.\" |
| 31.Dd June 16, 2004 | 31.Dd November 10, 2005 |
| 32.Dt ARP 4 33.Os 34.Sh NAME 35.Nm arp 36.Nd Address Resolution Protocol 37.Sh SYNOPSIS 38.Cd "device ether" 39.Sh DESCRIPTION --- 10 unchanged lines hidden (view full) --- 50ARP queues the message which requires the mapping and broadcasts 51a message on the associated network requesting the address mapping. 52If a response is provided, the new mapping is cached and any pending 53message is transmitted. 54ARP will queue at most one packet while waiting for a response to a 55mapping request; 56only the most recently ``transmitted'' packet is kept. 57If the target host does not respond after several requests, | 32.Dt ARP 4 33.Os 34.Sh NAME 35.Nm arp 36.Nd Address Resolution Protocol 37.Sh SYNOPSIS 38.Cd "device ether" 39.Sh DESCRIPTION --- 10 unchanged lines hidden (view full) --- 50ARP queues the message which requires the mapping and broadcasts 51a message on the associated network requesting the address mapping. 52If a response is provided, the new mapping is cached and any pending 53message is transmitted. 54ARP will queue at most one packet while waiting for a response to a 55mapping request; 56only the most recently ``transmitted'' packet is kept. 57If the target host does not respond after several requests, |
| 58the host is considered to be down for a short period (normally 20 seconds), 59allowing an error to be returned to transmission attempts during this 60interval. | 58the host is considered to be down allowing an error to be returned to 59transmission attempts. 60Further demand for this mapping causes ARP request retransmissions, that 61are ratelimited to one packet per second. |
| 61The error is 62.Er EHOSTDOWN 63for a non-responding destination host, and 64.Er EHOSTUNREACH 65for a non-responding router. 66.Pp 67The ARP cache is stored in the system routing table as 68dynamically-created host routes. 69The route to a directly-attached Ethernet network is installed as a 70.Dq cloning 71route (one with the 72.Li RTF_CLONING 73flag set), 74causing routes to individual hosts on that network to be created on 75demand. 76These routes time out periodically (normally 20 minutes after validated; 77entries are not validated when not in use). | 62The error is 63.Er EHOSTDOWN 64for a non-responding destination host, and 65.Er EHOSTUNREACH 66for a non-responding router. 67.Pp 68The ARP cache is stored in the system routing table as 69dynamically-created host routes. 70The route to a directly-attached Ethernet network is installed as a 71.Dq cloning 72route (one with the 73.Li RTF_CLONING 74flag set), 75causing routes to individual hosts on that network to be created on 76demand. 77These routes time out periodically (normally 20 minutes after validated; 78entries are not validated when not in use). |
| 78An entry for a host which is not responding is a 79.Dq reject 80route (one with the 81.Li RTF_REJECT 82flag set). | |
| 83.Pp 84ARP entries may be added, deleted or changed with the 85.Xr arp 8 86utility. 87Manually-added entries may be temporary or permanent, 88and may be 89.Dq published , 90in which case the system will respond to ARP requests for that host --- 19 unchanged lines hidden (view full) --- 110feature causes the local host to act as a proxy for 111.Em all 112hosts. 113It may be enabled by setting the 114.Xr sysctl 8 115MIB variable 116.Va net.link.ether.inet.proxyall 117to 1. | 79.Pp 80ARP entries may be added, deleted or changed with the 81.Xr arp 8 82utility. 83Manually-added entries may be temporary or permanent, 84and may be 85.Dq published , 86in which case the system will respond to ARP requests for that host --- 19 unchanged lines hidden (view full) --- 106feature causes the local host to act as a proxy for 107.Em all 108hosts. 109It may be enabled by setting the 110.Xr sysctl 8 111MIB variable 112.Va net.link.ether.inet.proxyall 113to 1. |
| 114.Sh MIB Variables 115The ARP protocol implements a number of configrable variables in 116.Va net.link.ether.inet 117branch 118of the 119.Xr sysctl 3 120MIB. 121.Bl -tag 122.It Dv prune_intvl 123How frequently the ARP cache is cleaned from expired entries. 124.It Dv max_age 125How long an ARP entry is hold in cache until it needs to be refreshed. 126.It Dv maxtries 127Number of retransmits before host is considered down and error is returned. 128.It Dv useloopback 129If an ARP entry is added for local address, force the traffic to go through 130the loopback interface. If set to 0 the traffic will be enforced to go 131through the hardware. 132.It Dv proxyall 133Enables ARP proxying for all hosts on net. 134.El |
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| 118.Sh DIAGNOSTICS 119.Em "arp: %x:%x:%x:%x:%x:%x is using my IP address %d.%d.%d.%d!" : 120ARP has discovered another host on the local network which responds to 121mapping requests for its own Internet address with a different Ethernet 122address, generally indicating that two hosts are attempting to use the 123same Internet address. 124.Pp | 135.Sh DIAGNOSTICS 136.Em "arp: %x:%x:%x:%x:%x:%x is using my IP address %d.%d.%d.%d!" : 137ARP has discovered another host on the local network which responds to 138mapping requests for its own Internet address with a different Ethernet 139address, generally indicating that two hosts are attempting to use the 140same Internet address. 141.Pp |
| 125.Em "arp: ether address is broadcast for IP address %d.%d.%d.%d!" : | 142.Em "arp: link address is broadcast for IP address %d.%d.%d.%d!" : |
| 126ARP requested information for a host, and received an answer indicating 127that the host's ethernet address is the ethernet broadcast address. 128This indicates a misconfigured or broken device. 129.Pp | 143ARP requested information for a host, and received an answer indicating 144that the host's ethernet address is the ethernet broadcast address. 145This indicates a misconfigured or broken device. 146.Pp |
| 130.Em "arp: %d.%d.%d.%d moved from %x:%x:%x:%x:%x:%x to %x:%x:%x:%x:%x:%x" : | 147.Em "arp: %d.%d.%d.%d moved from %x:%x:%x:%x:%x:%x to %x:%x:%x:%x:%x:%x on %s" : |
| 131ARP had a cached value for the ethernet address of the referenced host, 132but received a reply indicating that the host is at a new address. 133This can happen normally when host hardware addresses change, 134or when a mobile node arrives or leaves the local subnet. 135It can also indicate a problem with proxy ARP. 136This message can only be issued if the sysctl 137.Va net.link.ether.inet.log_arp_movements 138is set to 1, which is the system's default behaviour. --- 34 unchanged lines hidden --- | 148ARP had a cached value for the ethernet address of the referenced host, 149but received a reply indicating that the host is at a new address. 150This can happen normally when host hardware addresses change, 151or when a mobile node arrives or leaves the local subnet. 152It can also indicate a problem with proxy ARP. 153This message can only be issued if the sysctl 154.Va net.link.ether.inet.log_arp_movements 155is set to 1, which is the system's default behaviour. --- 34 unchanged lines hidden --- |