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Old 05-13-2018, 06:21 PM   #1
yvesjv
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Wink help with setting up ethernet only bridge between two different 802.1q trunk


Hi all,

This is a repost from a question I submitted earlier on the Slackware forum.
I'm hoping a linux networking could help with my setup or advise if I'm settting it up wrong.

Have a query towards setting up Slackware64 14.2 as a transparent ethernet bridge.
I have built this box with 3 interfaces to sniff packets for troubleshooting purposes.

eth0 is the management interface with an ip address configured so I can ssh into it.
eth1 connects to vlan 1200 with no ip address configured
eth2 connects to vlan 1300 with no ip address configured
vlan 1200 connects to eth1 via a switchport configured as a 802.1q trunk
vlan 1300 connects to eth2 via a different switchport also configured as a 802.1q trunk

The subnet is a simple 192.168.1.0/30 with vlan interfaces setup as
vlan1200 is 192.168.1.1
vlan1300 is 192.168.1.2

The interfaces eth1 and eth2 on the Slackware box plays nice when using brctl to create a bridge br0 for the two interfaces.

My search for information is always coming up with the setting up of ip addresses on both eth1 and eth2... which I'm trying to avoid.
I'm searching for the information towards how to strip/add on the fly the 802.1q tags coming in/out of the individual interfaces so I can sniff the ip packets passing through the bridge br0.

I would really appreciate it if you could please point me to a howto towards setting this up in Slackware?

Thanks a million in advance. :-)
 
Old 05-16-2018, 02:29 PM   #2
nini09
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Why do you need IP address on vlan1200 and vlan1300?
 
Old 05-16-2018, 06:27 PM   #3
yvesjv
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Talking

Quote:
Originally Posted by nini09 View Post
Why do you need IP address on vlan1200 and vlan1300?
Hi nini09,

The two switches have the SVIs with these ip addresses.
Trying to setup this up for packet sniffing and troubleshooting:
switch1/vlanX <===trunk===>Slackware sniffer<=====trunk=====>switch2/vlanY

If that works, then i can setup some IGP between the two switches or manual routing,
 
Old 05-17-2018, 02:48 PM   #4
nini09
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If you use Slackware for sniffer on VLAN interface, the IP address isn't necessary. Switch can have SVI with IP address but it doesn't mean that sniffer point(Slackware) need IP address.
 
Old 05-18-2018, 01:59 AM   #5
yvesjv
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Wink

Quote:
Originally Posted by nini09 View Post
If you use Slackware for sniffer on VLAN interface, the IP address isn't necessary. Switch can have SVI with IP address but it doesn't mean that sniffer point(Slackware) need IP address.
Thanks for the update, you are correct.
I've performed a simple setup to begin with and can sniff packets on the ports but they are not passing from eth1 to eth2... missing something here
I started with simple few commands:
ifconfig eth1 up
ifconfig eth2 up
brctl addbr br0
brctl addbr br0.1200
brctl addbr br0.1300
brctl addif br0.1200 eth1
brctl addif br0.1300 eth2
ifconfig br0 up
ifconfig br0.1200 up
ifconfig br0.1300 up

Haven't tried using the vconfig commands yet.
Will try next week and have a great weekend.
 
  


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