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Wed, 19 Nov 2025 18:43:13 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 5AJIhDDS011359 for bugs@FreeBSD.org; Wed, 19 Nov 2025 18:43:13 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 291100] Reduce ARP cache time from 20 minutes to 60 seconds Date: Wed, 19 Nov 2025 18:43:13 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: misc X-Bugzilla-Version: Unspecified X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: achillesgaikwad@gmail.com X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter attachments.created Message-ID: Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated List-Id: Bug reports List-Archive: https://lists.freebsd.org/archives/freebsd-bugs List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-bugs@FreeBSD.org MIME-Version: 1.0 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D291100 Bug ID: 291100 Summary: Reduce ARP cache time from 20 minutes to 60 seconds Product: Base System Version: Unspecified Hardware: Any OS: Any Status: New Severity: Affects Some People Priority: --- Component: misc Assignee: bugs@FreeBSD.org Reporter: achillesgaikwad@gmail.com Created attachment 265511 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D265511&action= =3Dedit patch to change arp time from 1200s to 60s This patch reduces the default ARP cache timeout (arpt_keep) from 1200 seco= nds (20 minutes) to 60 seconds to improve network responsiveness in dynamic environments, particularly cloud deployments. ## issue: The current 20-minute ARP cache timeout, while appropriate for traditional stable network environments (Like on-prem systems), causes connectivity iss= ues in modern cloud environments. It is not common that in on prem the IP pool = gets recycled quickly within 20 minutes. Where as in cloud environments -=20 1. Short-lived instances: Client systems may operate for less than 20 minut= es before termination, the IP address that the virtual machines held will be reused by other virtual machines. 2. Due to [1] when IP addresses are quickly reassigned to new virtual machi= nes, the OS continues attempting to communicate with the cached (now stale) MAC address instead of performing a fresh ARP resolution until 20 minutes. ## How are we solving this problem?: The patch modifies sys/netinet/if_ether.c by changing the arpt_keep variable initialization: - Before: VNET_DEFINE_STATIC(int, arpt_keep) =3D (20*60); (1200 seconds) - After: VNET_DEFINE_STATIC(int, arpt_keep) =3D 60; (60 seconds) ## Rationale: - Better suited for dynamic cloud environments with frequent IP recycling - Better out of the box experience for users, as users do not have to debug= and edit sysctl in their environment ## Downsides: - More ARP traffic but this is not going to affect CPU cycles or affect performance of OS in anyway. I hope! ## Is anyone else doing this already? - Yes, Linux has a default ARP cache time of 60 seconds. I tried to find is= sues that could happen due to arp cache time of 60 seconds but found nothing. ## Request: Please accept my patch where I make this modification for better out of the= box experience for users. --=20 You are receiving this mail because: You are the assignee for the bug.=