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Date: Wed, 20 Feb 2002 00:16:56 -0800 (PST)
From: Alexander Grebennikov <algr@rocc.ru>
To: freebsd-gnats-submit@FreeBSD.org
Subject: VLAN & bridging & MTU
X-Send-Pr-Version: www-1.0

>Number:         35136
>Category:       kern
>Synopsis:       VLAN & bridging & MTU
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    luigi
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Feb 20 00:20:01 PST 2002
>Closed-Date:    Mon Oct 03 10:26:03 GMT 2005
>Last-Modified:  Mon Oct 03 10:26:03 GMT 2005
>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:

From: "."@babolo.ru
To: algr@rocc.ru (Alexander Grebennikov)
Cc: freebsd-gnats-submit@FreeBSD.ORG
Subject: Re: kern/35136: VLAN & bridging & MTU
Date: Wed, 20 Feb 2002 21:44:53 +0300 (MSK)

 Alexander Grebennikov writes:
 > 
 > >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.
 As far as I remember ;-0
 level 3 only can fragment packets.
 So use routing, not bridging (level 2)
 to fragment packets
 
 -- 
 @BABOLO      http://links.ru/
Responsible-Changed-From-To: freebsd-bugs->luigi 
Responsible-Changed-By: luigi 
Responsible-Changed-When: Mon Nov 18 14:15:48 PST 2002 
Responsible-Changed-Why:  
remember to look at it 


http://www.freebsd.org/cgi/query-pr.cgi?pr=35136 

From: Yar Tikhiy <yar@FreeBSD.org>
To: freebsd-gnats-submit@FreeBSD.org, algr@rocc.ru
Cc: luigi@FreeBSD.org
Subject: Re: kern/35136: VLAN & bridging & MTU
Date: Thu, 11 Nov 2004 00:55:26 +0300

 I believe that this PR may be closed since its originator
 was trying to bridge traffic between interfaces with different
 MTU settings, which was not going to work for quite apparent
 reasons.  The relation of interface MTU to hardware MTU/MRU of
 the corresponding Ethernet NIC isn't obvious and depends on
 the driver implementation, but this issue could better be discussed
 in a separate PR if it really needs to.
 
 -- 
 Yar

From: Yar Tikhiy <yar@FreeBSD.org>
To: freebsd-gnats-submit@FreeBSD.org
Cc:  
Subject: Re: kern/35136: VLAN & bridging & MTU
Date: Thu, 11 Nov 2004 00:57:24 +0300

 BTW, the originator's email address is gone.
 
 -- 
 Yar

From: Pawel Malachowski <pawmal-posting@freebsd.lublin.pl>
To: bug-followup@FreeBSD.org
Cc:  
Subject: Re: kern/35136: VLAN & bridging & MTU
Date: Sat, 23 Jul 2005 21:01:29 +0200

 Yet another vote to close this very old PR.
 Bridge works with frames (which depend on hardware capabilities),
 originator wants to fragment packets.
 
 
 -- 
 Pawe Maachowski
State-Changed-From-To: open->closed 
State-Changed-By: yar 
State-Changed-When: Mon Oct 3 10:23:21 GMT 2005 
State-Changed-Why:  
bridge(4) has departed for /dev/null, the originator's 
mailbox has vanished, and consensus has been reached  
the problem itself isn't there.  Looks like the high 
time to close this PR. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=35136 
>Unformatted:
