From owner-freebsd-net@FreeBSD.ORG Wed Jun 25 00:01:10 2014 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 8F94FD47 for ; Wed, 25 Jun 2014 00:01:10 +0000 (UTC) Received: from mail-in6.apple.com (mail-out6.apple.com [17.151.62.28]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 683672E35 for ; Wed, 25 Jun 2014 00:01:09 +0000 (UTC) Received: from mail-out.apple.com (bramley.apple.com [17.151.62.49]) (using TLS with cipher RC4-MD5 (128/128 bits)) (Client did not present a certificate) by mail-in6.apple.com (Apple Secure Mail Relay) with SMTP id F7.AD.27911.5411AA35; Tue, 24 Jun 2014 17:01:09 -0700 (PDT) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; CHARSET=US-ASCII Received: from relay3.apple.com ([17.128.113.83]) by local.mail-out.apple.com (Oracle Communications Messaging Server 7.0.5.30.0 64bit (built Oct 22 2013)) with ESMTP id <0N7P002MB6NL2SQ1@local.mail-out.apple.com> for freebsd-net@freebsd.org; Tue, 24 Jun 2014 17:01:09 -0700 (PDT) X-AuditID: 11973e15-f79cf6d000006d07-9a-53aa1145fa89 Received: from [17.149.224.119] (Unknown_Domain [17.149.224.119]) (using TLS with cipher AES128-SHA (128/128 bits)) (Client did not present a certificate) by relay3.apple.com (Apple SCV relay) with SMTP id 5B.26.08757.7411AA35; Tue, 24 Jun 2014 17:01:11 -0700 (PDT) Subject: Re: MTU not regrowing? From: Charles Swiger In-reply-to: <53A9C6D0.3090900@netfence.it> Date: Tue, 24 Jun 2014 17:01:08 -0700 Message-id: <2CA56230-440A-4D77-83BD-222FBC704F70@mac.com> References: <53A9C6D0.3090900@netfence.it> To: Andrea Venturoli X-Mailer: Apple Mail (2.1510) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrLLMWRmVeSWpSXmKPExsUiON3OUNdVcFWwwdNeEYsPO9qZHBg9Znya zxLAGMVlk5Kak1mWWqRvl8CVsWoLS8FLzopVd9qYGxhvsHcxcnJICJhIvD3xmRnCFpO4cG89 WxcjF4eQwEwmiYdX/oAleAUEJX5MvsfSxcjBwSwgL3HwvCxImFlAS+L7o1YWiPp5TBLXutcz wgw9d/UmE0Sin0libcsdNpCEMFDzhVNNbCCD2ATUJCZM5AEJcwpoS/w9sJcFxGYRUJW4d6OH DWKXtMSCPzEQJ1hJLPzZxgoSFgLae/8oE0hYBKh68e0ZTBBbZSVOn3sOdo6EwHtWia33F7NO YBSeheSDWQgfzELywQJG5lWMQrmJmTm6mXlmeokFBTmpesn5uZsYIeEruoPxzCqrQ4wCHIxK PLwXZq8MFmJNLCuuzD3EKM3BoiTOq7lhRbCQQHpiSWp2ampBalF8UWlOavEhRiYOTqkGRp73 aYHVfY+6n5XuPGHG6fAkOU12VZn+VbaujMD0n56/ntyuMamv2mpyw7F7pf67gjcN6ZNrPCo0 ZMtWn7Vk7/dKsW8wU29we8q4as4Os09xIt+WSvjoqAUcnxx3NTauPkNYc/OVvmBVa7YjhZ0z JjY6b39R8/KtXv7GbTtLDpa9s/jW8bBFiaU4I9FQi7moOBEAARPfhEACAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprLLMWRmVeSWpSXmKPExsUiOPVBua674Kpgg3fHZS0+7Ghnsrh2o43d gcljxqf5LB4fl0xhDmCK4rJJSc3JLEst0rdL4Mo4feAle0EPV8XkiZ9YGxi/sHcxcnJICJhI nLt6kwnCFpO4cG89WxcjF4eQQD+TxMsbD9hAEswCWhI3/r0EKuLg4BXQk9j+Sw4kLCwgL3Hh VBMbSJhNQE1iwkQekDCngLbE5LUbwUayCKhK3LvRA1bCLCAtseBPDMRAbYllC18zQwy0klg1 pRbEFALac/8oWKMIUOPi2zOg7pKVOH3uOcsERv5ZSK6ZhXDNLCQzFzAyr2IUKErNSaw01kss KMhJ1UvOz93ECAq0hsLgHYx/llkdYhTgYFTi4b0we2WwEGtiWXFl7iFGCQ5mJRHeV6+BQrwp iZVVqUX58UWlOanFhxilOViUxHnPRiwOFhJITyxJzU5NLUgtgskycXBKNTCaff7s/f/44pNc QQcOrebOlH9/OPnV0fVb0iT2B3y86W9ntqhXcMrVjOB7ccynJX4pR1i6sVzbfFWOu1U/UfRb 1IFD+m7pwRcPLFeTvH1bOf7LoSfTuSNiZ/79/EdJ/Ihr1HF1azYmG3npE8f2NDJtq+KY7Wh8 8f3njT1syqkHO1+++F7nZhemxFKckWioxVxUnAgArwSpnTACAAA= Cc: freebsd-net@freebsd.org X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 25 Jun 2014 00:01:10 -0000 Hi-- On Jun 24, 2014, at 11:43 AM, Andrea Venturoli wrote: > Hello. > > Today I experienced something weird (at least for me) on a 8.4 system: > > _ the system had vlan3 interface, with default MTU (1500 bytes); > _ "ping -D -s 1400 somehost" would work, but "ping -D -s 1500 somehost" would yield "frag needed and DF set" (forgive me if the message is not exact, I don't have it anymore); > > _ to make some tests I reduced MTU size with "ifconfig vlan3 mtu 500"; > _ now, of course, "ping -D -s 400 somehost" would work, but "ping -D -s 500 somehost" would yield "frag needed and DF set"; > > _ then I raised MTU again with "ifconfig vlan3 mtu 1500" (notice ifconfig would actually report this as "mtu 1500" was shown); > _ however the results were as before, i.e. "ping -D -s 400 somehost" would work, but "ping -D -s 500 somehost" would yield "frag needed and DF set"; > > _ no way I could ping with a packet bigger than 500 bytes until I rebooted. > > Is this expected behaviour? Any way to get around this? Does "ifconfig vlan3 down; ifconfig vlan3 up" do any good? Or that run against the physical NIC? What is the ethernet HW; and are you using VLAN_HWTAGGING capability? Regards, -- -Chuck