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Date:      Wed, 02 Oct 2002 23:34:00 +0500
From:      "Ed Paquette" <ed@gtemail.net>
To:        freebsd-questions@freebsd.org
Subject:   Re: Setting Up VLAN IFaces for IDS
Message-ID:  <20021002183400.14209.qmail@verizonmail.com>

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Hi.

I agree with Mike's description of an (unconfigured) switch, but the issue 
comes after it since tcpdumping -i fxp1 (the parent) yields ALL packets 
(including unicasts).  This is what the switch was configured to do - forward 
all packets.

The issue is with the BSD box and the actual VLAN interface.

Any ideas why the vlan interfaces are truncating unicasts?

Thanks...
-ed

> In a switched network unicast packets from host A on port 1 to host b on
> port 2 will never be seen by host C on port 3 (whether it is a trunk or
> not).  That is the whole point of a switch.  Broadcast packets are always
> sent to all ports in in the VLAN (including trunks).
>
>> Greetings.
>>
>> My goal is to set up three vlan interfaces on a FreeBSD 4.6.2R box for use
>> with an IDS product.
>>
>> Currently, the switch to which the BSD box is connected is set up properly
>> with tagging enabled for the respective VLANS.
>>
>> I have a parent interface (fxp1) configured with no IP address.
>>
>> If I use TCPDUMP on the parent interface to test whether or not the tagged
>> packets are being received I get something like:
>>
>>  #tcpdump -i fxp1
>>  00:03:42.758875 802.1Q vlan#10 P0 ...
>>  <lots and lots of VLAN10 stuff here>
>>
>> Which to me implies that the packets are arriving at the BSD box 
>> appropriately tagged.
>>
>> So, I configure a vlan with no IP address:
>>
>>  #ifconfig vlan0 vlan 10 vlandev fxp1 up
>>
>> And when I do a:
>>
>>  #tcpdump -i vlan0
>>
>> All I get are broadcasts... ARPs, ICMP to something.255, etc for VLAN10. All
>> unicast packets for VLAN10 are dropped.
>>
>> Am I barking up a wrong tree?  Is it possible to do this?  Ideally, I'd like
>> to have the following:
>>
>> +------+                  +-------+
>> | FBSD | vlan0....VLAN#10 |       |
>> |      +-vlan1----VLAN#11-+ switch|
>> | IDS  | vlan2....VLAN#12 |       |
>> +--+---+                  +-+-+-+-+
>>  |                          | | |
>>  |                          | | \__VLAN#10
>>  \__iface with IP           | \____VLAN#11
>>                             \______VLAN#12
>>
-- 
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