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Date:      Tue, 29 Jan 2008 15:54:36 +0000
From:      Tom Judge <tom@tomjudge.com>
To:        Alexandre Biancalana <biancalana@gmail.com>
Cc:        freebsd-net@freebsd.org
Subject:   Re: VLAN problems
Message-ID:  <479F4C3C.5070801@tomjudge.com>
In-Reply-To: <8e10486b0801290439y77568aeby6c6dbfbb5132f61d@mail.gmail.com>
References:  <8e10486b0801290439y77568aeby6c6dbfbb5132f61d@mail.gmail.com>

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Alexandre Biancalana wrote:
> Hi list,
> 
>    I changed the company gateway implementing vlan concept and now I
> have a lot of slow and packet loss.
> 
>    I'm running FreeBSD FW1 7.0-PRERELEASE FreeBSD 7.0-PRERELEASE #0:
> Fri Jan 25 10:36:18 UTC 2008     root@FW1:/usr/obj/usr/src/sys/FW
> amd64
> 
>   This server is an Dell Power Edge 1950, QuadCore 2.83, 2Gb Ram, one
> bce gigabit interface connected to a gigabit port of a Cisco 4500 in
> trunk mode. There are 10 vlans configured on top of bce1 interface. I
> made this change last night and with small traffic all was ok, but
> with the increase of the traffic during normal daily usage, we are
> experiencing too much packet loss and slow connections.
> 
>   I change the mtu of bce to 9000, this help something but I still
> have bad performance. I think that this could be related with mtu, but
> I don't know where and what to change.

I have seen some problems if you try to run more than one MTU on 
different VLANS with the same parent interface.  For example if you set 
the parent interface MTU and vlan1 to 9000 and then tried to change 
vlan2 to have a 1500 byte mtu then the change of mtuon the vlan would 
also change the mtu on the parent.

If you are not running jumbo frames or nested vlans I don't think that 
changing the mtu of the interface is going to help you.  The output of 
ifconfig would also help people give you more help with this.

Tom
> 
>   Googling around I found some references that said to test mtu with
> ping and here are the results:
> 
> # ping -D -s 1473 192.168.0.5
> PING 192.168.0.5 (192.168.0.5): 1473 data bytes
> ping: sendto: Message too long
> ping: sendto: Message too long
> --- 192.168.0.5 ping statistics ---
> 6 packets transmitted, 0 packets received, 100.0% packet loss
> 
> # ping -D -s 1400 10.2.0.36
> PING 10.2.0.36 (10.2.0.36): 1400 data bytes
> 1408 bytes from 10.2.0.36: icmp_seq=0 ttl=64 time=86.026 ms
> 1408 bytes from 10.2.0.36: icmp_seq=1 ttl=64 time=5.558 ms
> --- 10.2.0.36 ping statistics ---
> 3 packets transmitted, 2 packets received, 33% packet loss
> round-trip min/avg/max/stddev = 5.558/45.792/86.026/40.234 ms
> 
> 
> Looking at netstat -ni output I have output errors too:
> 
>  # netstat -niW
> Name      Mtu Network       Address              Ipkts Ierrs    Opkts
> Oerrs  Coll
> bce0*    1500 <Link#1>      00:1d:09:67:8d:f1        0     0        0
>    0     0
> bce1     9000 <Link#2>      00:1d:09:67:8d:ef 83289870     0 80535996
>    0     0
> pflog0  33160 <Link#3>                               0     0  1153529
>    0     0
> lo0     16384 <Link#4>                          516657     0   516661
>    0     0
> lo0     16384 127.0.0.0/8   127.0.0.1          4041401     -   516661
>    -     -
> pfsync0  1460 <Link#5>                               0     0        0
>    0     0
> vlan2    1500 <Link#6>      00:1d:09:67:8d:ef 37445062     0 32727529
> 1047565     0
> vlan2    1500 10.2.0.0/16   10.2.0.36           636786     -  3000823
>    -     -
> vlan11   1500 <Link#7>      00:1d:09:67:8d:ef 33865371     0 36676651
> 993848     0
> vlan11   1500 10.11.0.0/16  10.11.0.1            51270     -  1147250
>    -     -
> vlan16   1500 <Link#8>      00:1d:09:67:8d:ef      388     0       19
>    0     0
> vlan16   1500 10.16.0.0/24  10.16.0.1                5     -       13
>    -     -
> vlan20   1500 <Link#9>      00:1d:09:67:8d:ef     1483     0        1
>    0     0
> vlan20   1500 10.20.0.0/24  10.20.0.1              636     -        0
>    -     -
> vlan200  1500 <Link#10>     00:1d:09:67:8d:ef      390     0        3
>    0     0
> vlan200  1500 10.200.0.0/30 10.200.0.1               0     -        0
>    -     -
> vlan201  1500 <Link#11>     00:1d:09:67:8d:ef    19153     0    19274
> 3408     0
> vlan201  1500 10.200.0.4/30 10.200.0.5               0     -        0
>    -     -
> vlan202  1500 <Link#12>     00:1d:09:67:8d:ef     8338     0     6694
> 1074     0
> vlan202  1500 10.200.0.8/30 10.200.0.9               0     -        0
>    -     -
> vlan203  1528 <Link#13>     00:1d:09:67:8d:ef  1691886     0  1429174
> 86768     0
> vlan203  1528 192.168.0.0/2 192.168.0.1          35672     -    31375
>    -     -
> vlan204  1500 <Link#14>     00:1d:09:67:8d:ef     1256     0        3
>    0     0
> vlan204  1500 10.0.0.84/30  10.0.0.85                0     -        0
>    -     -
> vlan205  1500 <Link#15>     00:1d:09:67:8d:ef 10256373     0  9676750
> 626525     0
> vlan205  1500 10.0.0.8/30   10.0.0.9           2509909     -  2667896
>    -     -
> 
> 
>  Any help is very appreciated,
> 
>  Regards,
> Alexandre Biancalana
> 
> PS: Please cc me, because I'm not subscribed in the list.
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