3Com SuperStack 3 switch with Cisco router

[pax_2111]

Hi,

I have a client that wants to install 3Com SuperStack 3 Switch 3300 switches and configure VLANs. They have a Cisco 2600 for routing & Internet connectivity.

I configured the router FastEthernet interface for multiple VLANs with dot1q encapsulation. But I can ping through VLAN 1 only.

--------------------router config ----------------------

interface FastEthernet0/0.1

encapsulation dot1Q 1 native

ip address 192.168.1.254 255.255.255.0

!

interface FastEthernet0/0.2

encapsulation dot1Q 2

ip address 192.168.2.254 255.255.255.0

------------------------------------------------------------

My question is:

Has anyone done something similar before? Are the two equpment compatible as far as 802.1q is concerned?

Also from what I understood from the documentation of the switch, a trunk in 3Com is not the usual trunk in Catalyst switches. So basically the port connecting to the router should be added to multiple VLANs to carry VLAN tagged info. Can anyone correct me on this?

thanx in advance

regards

[donewald]

Making your VLAN1 subinterface "native" would make traffic from this untagged so this might be why it's working. It's been a long time since I've worked with 3Coms but I think that you can configure trunks on them, rather than just assigning multiple VLANs to the port. I would suspect the 3Com configuration in this case.

Hope this helps,

Don

[hramtsov]

Hi,

I don't think that you right. I'm successfully using this configuration:

---- cut here -----

interface FastEthernet0/0

no ip address

!

interface FastEthernet0/0.11

encapsulation dot1Q 1 native

ip address 10.0.0.1 255.255.255.0

!

interface FastEthernet0/0.12

encapsulation dot1Q 12

ip address 10.0.1.1 255.255.255.192

----- cut here -----

Of course, IPs changed.

[donewald]

In no way did I say this configuratoin would not work. I merely stated that if VLAN 1 is untagged (NATIVE) and that is the only VLAN that is functioning (passing traffic) then the 3Com is not setup properly more than likely. That make more sense?

Hope so,

Don

[hramtsov]

Hello,

My company successfully using 3Com SuperStack II switches and Cisco 7206 with VLANs without any problems. I do not think you expiriencing problem because of hardware incompatibility.

If I understand your second question correctly, trunk in 3Com is a port-channel in cisco. Each port in 3Com that belonged to any VLANs using 802.1Q encapsulation is a trunks in "cisco notation".

I hope I've partly answered your questions.

[ucivan]

Hi;

I have nearly the same problem.In some older IOS even you make a proper configuration router waits a tagged frame from Ethernet interface not the sub interface.Therefore I think this configuration will work.

interface FastEthernet0/0

ip address x.x.x.x x.x.x.x -------------->which is vlan 1 default gateway.

interface FastEthernet0/0.1

!

interface FastEthernet0/0.2

encapsulation dot1Q 2

ip address 192.168.2.254 255.255.255.0

I will pleased if you let me know if it works.

Regards

[raarons]

The issue is quite straightforward. I have implemented this type of connectivity for many customers.

By default, Cisco devices maintain a "native" vlan on a trunk, which does NOT carry 802.1Q tagging on frames (although if a frame is received with an 802.1Q tag associating it to the native vlan, the Cisco device accepts it properly).

By default 3Com devices, however, tag all frames sent onto an 802.1Q trunk, and disregard untagged frames received.

The solution is either to encapsulate all vlan traffic on the Cisco (to match the 3Com), or untag the native vlan traffic on the 3Com (to match the Cisco). I prefer the latter. Exactly how you do this depends on which 3Com device you are configuring, and whether through the CLI or by web management.

Hope this helps

[raarons]

I should have added that you can only tag the native vlan traffic on some Cisco devices, such as CatOS-based switches with the set-dot1q-all-tagged command.