[c-nsp] Cisco 3700, SMC TigerSwitch, Linux and VLAN Problems

Ray Van Dolson rayvd at digitalpath.net
Fri Jun 2 00:41:11 EDT 2006


Hope this isn't too off topic.


                ^
                | FastEth0/0 (WAN)
    +--------------+
    |  Cisco 3700  |
    +-----------+--+
                |                                 +-----------------+
    FastEth0/1  |                                 | SMC TigerSwitch |
                +---------------------------------+-----------------+
             FastEth0/1.1                    Port 1                 | Port 23
               dot1Q 1 native                                       |
               192.168.100.1/24                             +-------+
             FastEth0/1.2                                   | 
               dot1Q 2                                      | eth1
               192.168.75.17/30                     +-------+ 192.168.75.18/30
                                                    | Linux |
                                                    +-------+


I'm trying to get VLAN tagging set up with a Cisco 3700 router, an SMC
TigerSwitch 6724AL2 and a Linux box.  The layout is as above.

I have my VLAN configuration configured as follows on the TigerSwitch:

(This is an 802.11Q configuration)

vlan database
 vlan 1 name DefaultVlan media ethernet state active
 vlan 2 name RayVlan media ethernet state active
!
interface ethernet 1/1
 switchport native vlan 1
 switchport mode trunk
 switchport allowed vlan add 1-2 tagged
!
...
!
interface ethernet 1/23
 switchport allowed vlan add 1-2 untagged
 switchport native vlan 2
!
interface vlan 1
 ip address 192.168.100.2 255.255.255.0
!

>From what I understand packets leaving the Cisco destined for 192.168.75.18
should be tagged for VLAN 2.  The SMC switch should send the packet out Port
23 and remove the VLAN tagging since the port is configured as untagged.

Packets coming in from the Linux box into Port 23 and destined for
192.168.75.17 should be tagged with VLAN 2 because of the "native vlan 2"
configuration option on the port (basically any untagged packets are tagged
for VLAN 2).  The switch should send this packet through Port 1 and the Cisco
sends it to the correct subinterface because of the VLAN tag.

However, traffic is not passing as I expect it go.  If I run a ping from the
Cisco to 192.168.75.18 while running a tcpdump on the Linux box's eth1, I
don't see the ICMP packets nor do I even see any ARP requests.

Can anyone see anything obviously wrong with my setup?  Maybe I have something
conceptually wrong.

Thanks,
Ray


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