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Old 03-02-2009, 02:45 PM   #1
Paris Heng
Registered: Jul 2007
Location: Kuala Lumpur, Malaysia
Distribution: Ubuntu 8.04, Solaris 10
Posts: 198

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Help in Vlan-Interface

1. What it means by eth1.200? I know it is a subinterface, but did it means this interface will carry Vlan tag 200?

2. eth1.200, will any ip packets that going out this interface will be tagged with VLAN tag 200?

3. [eth1-----Trunk------Cisco Switch] it is the configuration same with
[eth1.300-----Trunk------Cisco Switch] ?

Last edited by Paris Heng; 03-02-2009 at 02:47 PM.
Old 03-02-2009, 06:20 PM   #2
Registered: Aug 2003
Location: Seattle
Distribution: ubuntu, lately
Posts: 182
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in a nutshell 1) yes, 2) yes, 3) no -- the Cisco port must be tagged w/ vlan 300.

to demo this for yourself:

sudo vconfig add eth0 52
sudo ifconfig eth0.52 netmask

ping -nq -c 20 &

sudo tcpdump -nc2 -i eth0 vlan
sudo tcpdump -nc2 -i eth0.52 arp

output from first tcpdump shows the vlan tag:
15:18:10.496264 vlan 52, p 0, arp who-has tell
15:18:11.496300 vlan 52, p 0, arp who-has tell

output from the second tcpdump shows the untagged arp pkts:
15:18:12.504295 arp who-has tell
15:18:13.504298 arp who-has tell

Last edited by grepmasterd; 03-02-2009 at 06:22 PM.


tcpdump, vconfig, vlan

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