Date: Wed, 20 Feb 2002 00:16:56 -0800 (PST) From: Alexander Grebennikov <algr@rocc.ru> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/35136: VLAN & bridging & MTU Message-ID: <200202200816.g1K8GuH51911@freefall.freebsd.org>
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>Number: 35136
>Category: kern
>Synopsis: VLAN & bridging & MTU
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Feb 20 00:20:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator: Alexander Grebennikov
>Release: tried many up to 4.4-RELEASE
>Organization:
RCC
>Environment:
FreeBSD x2.rocc.ru 4.4-RELEASE FreeBSD 4.4-RELEASE #0: Thu Dec 20 11:11:47 MSK 2001
>Description:
I'm trying to bridge traffic between 2 VLANs using FreeBSD in BRIDGE mode.
Channel between 2 VLANS going through G.703.
There are 2 G.703<-->Ethernet converters at both sides.
Converters are modems. These modems cannot pass VLAN packets because VLAN packets are 4 bytes large then usual.
What i did: setting up 1-st interface on FreeBSD with MTU=1500 , second interface ( to converter) with MTU=1400. Started BRIDGE mode.
Packets not fragmented passing FreeBSD. :(
And still getting out to converter with MTU=1500 via ethernet interface with MTU=1400 !! I think it's a bug ??
>How-To-Repeat:
Need 3 computers:
2 of them - usual PCs with 1 Ethernet card each.
3-rd = FreeBSD in Bridge mode with 2 ethernet cards. 1 card must be setted MTU=1500. Second card - MTU=1400
E.g.
PC1 <--(MTU_1500)-->FreeBSD_BRIDGE<--(MTU_1400)--> PC2
Ping PC2 from PC1 with packet size=4000 byes (for example)
Start to sniff packets from PC1 on PC2. They should have maximum size=1400 bytes ! But they will have size =1500 ! That is bug.
>Fix:
I don't know....
>Release-Note:
>Audit-Trail:
>Unformatted:
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