Extend VLAN from 3550 to 2950 switch?

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Sep 26th, 2008
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I have a 3550 switch a number of VLANS, 2 to 5 to be exact. I need VLAN 5 to extend over to the 2950.

Would simply trunking the 2 switches solve this, by using dot1q trunk on a port on each switch?

The complicated part comes when I then have to give VLAN 2 on the 3550 (servers) access to VLAN 6 (servers) on the 2950.

One switch is L2 and the other L3, so I'm not sure if the L3 switch (3550) can provide the InterVLAN info or not.

Anyway let me know what you think?


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Prashanth Krishnappa Fri, 09/26/2008 - 06:19
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Make sure you have all the VLANs created in the 2950(if you are not using VTP server/client mode but using transparent mode) and configure the interfaces to be dot1q trunks.

Yes, your 3550 can do intervlan routing and you can configure Access-lists to filter traffic as well.

Following tech tip should help as well


VictorAKur Fri, 09/26/2008 - 06:20
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trunking two switches together will work.

To provide intervlan routing configure two VLAN interfaces on the 3550 with IP addresses corresponding to each VLAN. That will do it.

Adam Frederick Fri, 09/26/2008 - 06:20
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Shouldnt be an issue.

Setup VTP and make the 3550 the "Server" and the 2950 the "Client"

You'll just have to config VLANs on the 3550 and they'll be propogated to the 2950.

As you said, you will need a "trunk" link between the 2.

Trunk links are made to carry multiple VLANs versus and "access" link which is made to carry just 1 VLAN.

Just set the default route on the 2950 to the 3550 and life will be good.


VictorAKur Fri, 09/26/2008 - 06:25
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You would also need to make sure taht the VTP domain name is the same on both switches in this case.

To avoid possible problems set the domain name on 3550 first. Then set the name on the 2950 to something random and then back to the domain name you will use (if you go down VTP route). This will start the VTP revision number on the 2950 from 0 and thus prevent it from possibly messing yiur VLANs up on the 3550.

I would not use VTP in a simle set up like this though.

Marwan ALshawi Sat, 09/27/2008 - 06:13
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VTP help u tp extend vlans over group of switches u need to have the main switch as the VTP server and others client

the switch in VTP client mode and in the same domain to a switch in vtp server mode

the client will pull vlans from the server one and u only need to assigne these vlans to ports on the client switch

if u have the 3550 as VTP server and a group of switches connected to that switch and they are in client mode u only ned to creat the L2 vlan on the 3550 switch and the vlans will be pull from those switches

it is time and efforts saving

the commands

VTP mode server


VTP mode client

VTP domain [domain name]

this name must be the same on all switches the clients and thier server to get it work

for verifications

show VTP status

good luck

if helpful Rate

whiteford Sat, 09/27/2008 - 06:33
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Thanks, do you know if the 2550 and 3550 support Auto-MDIX? As I think I might need a crossover for this trunk. I would of thought the 3550 supports Auto-MDIX.


IOS - c2950-i6q4l2-mz.121-22.EA12.bin


IOS - c3550-ipservices-mz.122-40.SE

Marwan ALshawi Sat, 09/27/2008 - 07:29
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not sure sorry !

please rate the helpful post

good luck

Marwan ALshawi Fri, 09/26/2008 - 06:52
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it is as simple as the following

on the L2 switch make the link to the 3550 as trunk

on the 3550 do the following

cteat L2 and L3 vlan

vlan 2

interface vlan 2

ip address

no shut

vlan 6

interface vlan 6

ip address

no shut

then enable ip rputing

ip routing

now on the hosts connected to 2950 and belong to vlan 2 thier defualt gateway must be vlan 2 interface like

and vlan 6 hosts

this way u will route between vlans

and u need the L2 vlan created on the 2950 as well like

vlan 2

good luck if helpful Rate


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