Aaron,
Thank you very much for your elaborate answer. I will make full use of your advice and hopefully I should achieve more than what i thought. In the meantime i also forward your useful info to the whole VLAN community as it may be very useful to most other members too.
Best Regards,
Cyprian.
---------------
"Brown, Aaron F" <aaron.f.brown@xxxxxxxxx> wrote:
v\:* {behavior:url(#default#VML);}o\:* {behavior:url(#default#VML);}w\:* {behavior:url(#default#VML);}.shape {behavior:url(#default#VML);}
Testing the VLAN configuration depends on what equipment you have. If you are using a switch that supports 802.1q VLANs, simply getting it running in a manner where your system with VLAN enabled is connected to tagged ports (configured for the VLANs in question) on the switch and confirm connectivity (ping) with systems connected to non tagged ports configured for the VLANs in question on the same switch. These systems should not have a VLAN driver on them as the switch will take care of adding and stripping the VLAN tags for any systems that are not connected to a ?tagged? port.
Are you familiar with packet sniffers? I personally like ?ethereal? (an xwindow based packet sniffer) but any software that can capture and display packets will do
If you connect the VLAN configured adapter to a hub (or to a switch that lets you monitor traffic from on the switch on a single port [often called mirroring a port, Cisco calls it spanning a port] you should be able to view the packets and see the VLAN tags. Unless your Ethernet driver is too smart and strips the tags for you ;-) See http://www.ethereal.com/, and search google for words like ?802.1Q? and ?packet capture? for more info in this line.
What you are looking for is a packet with an ethertype of 8100 in hex, the fields (4 hex digits) following the ethertype of an 802.1Q tagged packet define a priority scheme and the VLAN ID. The first hex digit (8 bits) is defines the priority and can essentially be ignored as far as VLANs are concerned, the other three bits are the VLAN ID. Translating them from hex to decimal gives you the decimal value of the VLAN, e.g. if my tags value is ?01ef?, ?0? is the priority bit and ?1ef? is the VLAN ID, which when converted to decimal is 495, e.g. VLAN ID 485. This alludes to an answer for the question you sent after this, of how many hex bits are used for VLAN. The answer is the VLAN Tag data consists of 4 hex digits, but only 3 of them are involved with VLANs.
Hope this helps,
Aaron
---------------------------------
From: Cyprian Clement [mailto:cyprian_clement@xxxxxxxxxxx]
Sent: Friday, March 18, 2005 4:21 AM
To: Brown, Aaron F
Subject: RE: [VLAN] VLAN Drivers
Hi Aaron,
Many thanks for your useful info. We have a specific test where we need to have a possibility of several VLANs with the same IP addr. I thought with vlan you can have this by thinking that vlan ID represented a subnet in itself. From your clarification it clearly looks i was wrong. I appreciate your feedback.
By the way do you know of any way or linux tool i can use to test the vlans i have created on on my linux machines. In other words to try at linux level to send packets over different vlans and check if they are mapped/sent to a correct vlan(s).
Again, thanks so much.
Best Regards,
Cyprian.
--------------
"Brown, Aaron F" <aaron.f.brown@xxxxxxxxx> wrote:
Treat each VLAN more or less the same as if they were physical NICs. Each VLAN ID represents a different collision domain (different subnet.) Give each VLAN interface an IP address on a different IP subnet and traffic will get routed out the appropriate VLAN for the subnet.
In other words, on machine one (eth2 w/ VLAN ID 2 and VLAN ID 3), give:
VLAN ID 2 an address of say 10.1.0.58
VLAN ID 3 an address of say 11.1.0.58
And on machine two give:
VLAN ID 2 an address of say 10.1.0.59
VLAN ID 3 an address of say 11.1.0.58
This assumes a subnet mask of 255.0.0.0. If you were to subnet it to 255.255.0.0, VLAN 2 could be 10.1.0.58 and VLAN 3 could be 10.3.0.58 and still be on separate subnets.
I do not believe the VLAN technology is intended to have the same IP address, or even the same IP subnet on the separate VLANs, if what you are trying to accomplish requires / expects that you may want to look at the bridge.o module and the brctl configuration tool.
Good luck,
Aaron
---------------------------------
From: vlan-bounces@xxxxxxxxxxxxxxx [mailto:vlan-bounces@xxxxxxxxxxxxxxx] On Behalf Of Cyprian Clement
Sent: Thursday, March 17, 2005 12:03 PM
To: vlan@xxxxxxxxxxxxxxx
Subject: [VLAN] VLAN Drivers
Hello community,
My name is Cyprian Clement. I am currently in an early stage in doing some Linux VLAN configuration. I have two Linux machines whereby one is running kernel 2.4.21-144(SUSE 9.0) and the other 2.6.4-52(SUSE 9.1). I have installed the VLAN drivers and it works fine.
The question I have is how can I send packets across different desired VLANS? Is there any tool(s) or means to achieve this? Also once i achieve this is there any way/tool i can verify that packets are actually going to and reaching the desired vlan/destination?
I have created VLANS using the vconfig command as follows:
1. one first machine i have eth2 with vlans 2 and 3. both vlans i have assigned the same ip i.e. 10.1.0.58
2. on the second machine i have eth3 with vlans 2 and 3. both vlans i have assigned same ip 10.1.0.59
Your help will be much much appreciated
Many Thanks in advance,
Cyprian Clement
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