Date: Sat, 02 Aug 2003 17:12:17 +0600 From: Boris Kovalenko <boris@tagnet.ru> To: freebsd-current@freebsd.org Subject: Re: bge & vlan stranges Message-ID: <3F2B9C91.7010300@tagnet.ru> In-Reply-To: <3F2B787D.D1C4BCAC@mindspring.com> References: <3F2A2B17.4020700@tagnet.ru> <3F2B787D.D1C4BCAC@mindspring.com>
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Terry Lambert wrote: Hello! >Boris Kovalenko wrote: > > >> I have Compaq DL360G2 with Broadcom BCM5701 Gigabit Ethernet and >>FreeBSD 5.1R installed. There are no problems if I use bge as usual >>network card, but when I try to use 802.1Q vlans, I can't receive (only >>receive, sending is ok) packets more then 1456 bytes! What is the >>problem? BGE driver, VLAN driver or my network configuration? >> >> > >The encapsulation information is subtracted from your available >MTU, so that is correct. > >Some cards have a bogus feature that lets you send longer frames >than the normal MTU, but you can't rely on this feature being >interoperable between card vendors, or being supported on all >cards. > >I suppose you want to do this because you are trunking a channel >that goes to a border device, and for some reason you have disabled >receipt of all ICMP, instead of only abusable ICMP, and thus you >have broken end-to-end path MTU discovery. > >It would be best if you were to simply fix your ICMP. > > No, this is test machine, I have installed it two days ago and have firewall_type="OPEN" in my settings. So I have not disabled MTU path discovery You are speaking of. Nevertheless, what is "substracted from available MTU?" Why? The correct way it should work: 1500 bytes packet + 14 bytes ethernet header + 4 bytes CRC = 1518 bytes is standard ethernet frame and 1500 bytes packet + 14 bytes ethernet header + 4 bytes 802.1Q tag + 4 bytes CRC = 1522 bytes of standard 802.1Q encapsulated frame. All 802.1Q realizations I know working the same. >-- Terry > > > Boris
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