Switching dilema continues

Unanswered Question
Apr 18th, 2008

Hello yet again,


HP Procurve switch:

- ports are assigned to "VLANs", but are untagged

Cisco 2948g L3 switch:

- not configured at all

- more of a router then a switch

Cisco 3500XL switch:

- not configured


- When I plug a cable into the HP switch in a port configured in the LAB vlan (172.16) I am assigned an address.

- If I run a line from the HP (plugged into lab) to a Cisco 3500XL switch and connect it then anyone I plug into that switch can now be assigned a 172.16 address.

- When I run a line to my Cisco 2948g L3 switch and plug it in the link comes up. If I plug in a user they are NOT assigned an address.


I would like to have it so that I can use the Cisco 2948g L3 switch so that anyone who plugs in can be assigned an address.


1. If the frames are untagged (on the HP) then are there really VLANs or are the ports just seperated by network subnets?

2. Why is it that the 3500XL switch has no trouble when I plug users into it (after the line has been ran from the HP).

3. Since the 2948g L3 acts more like a router, could I assign an address to the port connecting the 2 switches and use a routing protocol to share host information?

4. If I tag the frames on the HP switch, then could I just create a trunk line between the two switches? If so, I have found information on configuring a Cisco 2948g L3 to do 802.1q, but would I need to change anything on the HP (set the ports to use encapsulation 802.1q? I would think if I tagged them that it would automattically use 802.1q)

Does anyone have any thoughts. I was hoping this 2948 switch would go without issues, but sadly it is more complex then what I thought. Knowing the end goal does anyone have any ideas?

I have this problem too.
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rebrokenglass Wed, 04/23/2008 - 06:53

Well I am sad to see that this post was never viewed, but thats ok. I figured out how to complete my setup. Configuration will follow for the record (or any other soul who was in my situation).

For the HP switch I has to put the ports I wanted into tagging mode. After this was done I went to the 3500 switch. I ran two trunk lines to this switch (both tagged on the HP end) and did the normal switchport mode trunk. I told each trunk line to only carry a certain VLAN's data. I assigned the ports each into their respective VLANs and it worked great. The tricky part of all of this was getting the 2948g l3 switch to work. The switch itself is more of a router then a switch. Each port is treated as a routable interface. To have them talk together you must bond them with a bridge. Config below:


interface FastEthernet1.1

encapsulation dot1Q 172

ip address

no ip directed-broadcast

bridge-group 1


interface FastEthernet2

no ip address

no ip redirects

no ip directed-broadcast

bridge-group 1

bridge-group 1 spanning-disabled


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