| arp.4 (348238dbd42306d9fb5d89ab393b840572cfeb0f) | arp.4 (0da3f8c98d17d9c6e67d0f6cf45085df6a5ef041) |
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| 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. --- 26 unchanged lines hidden (view full) --- 35.Nm arp 36.Nd Address Resolution Protocol 37.Sh SYNOPSIS 38.Cd "device ether" 39.Sh DESCRIPTION 40The Address Resolution Protocol (ARP) is used to dynamically 41map between Protocol Addresses (such as IP addresses) and 42Local Network Addresses (such as Ethernet addresses). | 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. --- 26 unchanged lines hidden (view full) --- 35.Nm arp 36.Nd Address Resolution Protocol 37.Sh SYNOPSIS 38.Cd "device ether" 39.Sh DESCRIPTION 40The Address Resolution Protocol (ARP) is used to dynamically 41map between Protocol Addresses (such as IP addresses) and 42Local Network Addresses (such as Ethernet addresses). |
| 43This implementation maps IP addresses to Ethernet, 44ARCnet, 45or Token Ring addresses. | 43This implementation maps IP addresses to Ethernet addresses. |
| 46It is used by all the Ethernet interface drivers. 47.Pp 48ARP caches Internet-Ethernet address mappings. 49When an interface requests a mapping for an address not in the cache, 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. | 44It is used by all the Ethernet interface drivers. 45.Pp 46ARP caches Internet-Ethernet address mappings. 47When an interface requests a mapping for an address not in the cache, 48ARP queues the message which requires the mapping and broadcasts 49a message on the associated network requesting the address mapping. 50If a response is provided, the new mapping is cached and any pending 51message 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. | 52ARP will queue at most 53.Va net.link.ether.inet.maxhold 54packets while waiting for a response to a mapping request; 55only the most recently ``transmitted'' packets are kept. |
| 57If the target host does not respond after several requests, 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. 62The error is 63.Er EHOSTDOWN 64for a non-responding destination host, and 65.Er EHOSTUNREACH 66for a non-responding router. 67.Pp | 56If the target host does not respond after several requests, 57the host is considered to be down allowing an error to be returned to 58transmission attempts. 59Further demand for this mapping causes ARP request retransmissions, that 60are 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 |
| 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). | 67The ARP cache is stored in per-interface link-level table. |
| 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 --- 81 unchanged lines hidden (view full) --- 168second. 169Default is 1 log message per second. 170.It Va max_age 171How long an ARP entry is held in the cache until it needs to be refreshed. 172Default is 1200 seconds. 173.It Va maxhold 174How many packets to hold in the per-entry output queue while the entry 175is being resolved. | 68.Pp 69ARP entries may be added, deleted or changed with the 70.Xr arp 8 71utility. 72Manually-added entries may be temporary or permanent, 73and may be 74.Dq published , 75in which case the system will respond to ARP requests for that host --- 81 unchanged lines hidden (view full) --- 157second. 158Default is 1 log message per second. 159.It Va max_age 160How long an ARP entry is held in the cache until it needs to be refreshed. 161Default is 1200 seconds. 162.It Va maxhold 163How many packets to hold in the per-entry output queue while the entry 164is being resolved. |
| 176Default is one packet. | 165Default is 16 packets. |
| 177.It Va maxtries 178Number of retransmits before a host is considered down and an error is 179returned. 180Default is 5 tries. 181.It Va proxyall 182Enables ARP proxying. 183Turned off by default. 184.It Va wait --- 67 unchanged lines hidden --- | 166.It Va maxtries 167Number of retransmits before a host is considered down and an error is 168returned. 169Default is 5 tries. 170.It Va proxyall 171Enables ARP proxying. 172Turned off by default. 173.It Va wait --- 67 unchanged lines hidden --- |