VLANs between C2950G & 3C16475BS?

[SYQUEST]

Is it possible to VLAN between Cisco C2950G and 3COM 3C16475BS? What steps would be needed to configure it?

Also are the fiber interfaces compatible using 1000BASE-SX, GBIC G5484 to SFP 3CSFP91?

 

[ADB100]

As long as both ends support 1000BaseSX the link should come up OK.
With regards to VLAN's - yes this will work but you obviously need to configure things. The Cisco end will need to be hard-coded as an 802.1q Trunk, it will also need the Native VLAN configuring (this will be the single Un-Tagged VLAN on the 3Com end). You will need to manually define your VLAN's and configure which VLAN's are allowed on the trunk.
The Cisco configuration will look like this:

interface GigabitEthernet0/1
switchport trunk native vlan 4000
switchport trunk allowed vlan 10,20,30
switchport mode trunk
switchport nonegotiate

I am not sure about the 3Com end but basically you need to configure the interface as a Trunk (or allow Mutliple Tagged VLAN's on it). The single Un-Tagged VLAN must match the Cisco 'Native VLAN', and the various Tagged VLAN's must match the Cisco 'allowed vlan' list.

The more worrying thing in my eyes would be the STP configuration.......

HTH

Andy

 

[SYQUEST]

Hi ADB100,

Thanks for your response. I have never setup a VLAN, but if I understand the idea, it is like dedicating a group of switch ports all connected to one another as a private circuit.

So to provide a dedicated path between the two locations, I build a set of parameters that are programmed in each switch that has ports in the designated VLAN?

I don't think STP would be an issue since the switches only have one physical connection between them. Right now it is fiber with media converters on both ends. In the C2950G STP is at default.

I'll also read the Cisco config guide to better understand VLANs and ask more questions.

....JIM....

 

[ADB100]

If its just a couple of switches then it should be OK.

Create the VLAN's on the Cisco 2950:

vtp mode transparent
!
vlan 10
name VLAN-10
!
vlan 20
name VLAN-20
!

Add the 802.1q trunk configuration as I listed earlier. Create the VLAN's on the 3Com (?), create the VLAN's on the 3Com switch, set the untagged VLAN (Native) on the Gigabit Interface and finally add the Tagged VLAN's to the Gigabit Interface.

To route between the VLAN's you will need a Layer-3 switch or router, otherwise as you said you will just have some Layer-2 networks spanned between a Cisco and 3Com switch.

HTH

Andy

 

[SYQUEST]

Your info is just what I needed. I will let you know how this works out when I set it up next week.

Thanks much!

....JIM....

 

[SYQUEST]

Well I got the VLAN setup and it appeared to work OK in the computer room. But now that I have installed it in it's permanent location I can't get "continuity". Could this have something to do with VTP or is there a way to have the switch broadcast the VLAN info?

Here is the config, if you need anything else let me know:

C2950-SW1#SHOW RUNNING-CONFIG
Building configuration...

Current configuration : 1847 bytes
!
! Last configuration change at 18:46:52 UTC Fri Sep 8 2006
! NVRAM config last updated at 18:49:00 UTC Fri Sep 8 2006
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log datetime
no service password-encryption
service sequence-numbers
!
hostname C2950-SW1
!
enable secret 5 $1$MHE0$mUXK8pYX/MbRwJvrwboX21
!
!
vlan 2
name SDS-2
ip subnet-zero
vtp mode transparent
!
spanning-tree extend system-id
!
!
interface FastEthernet0/1
no ip address
!
interface FastEthernet0/2
no ip address
!
interface FastEthernet0/3
no ip address
!
interface FastEthernet0/4
no ip address
!
interface FastEthernet0/5
no ip address
!
interface FastEthernet0/6
no ip address
!
interface FastEthernet0/7
no ip address
!
interface FastEthernet0/8
no ip address
!
interface FastEthernet0/9
no ip address
!
interface FastEthernet0/10
no ip address
!
interface FastEthernet0/11
no ip address
!
interface FastEthernet0/12
no ip address
!
interface FastEthernet0/13
no ip address
!
interface FastEthernet0/14
no ip address
!
interface FastEthernet0/15
no ip address
!
interface FastEthernet0/16
no ip address
!
interface FastEthernet0/17
no ip address
!
interface FastEthernet0/18
no ip address
!
interface FastEthernet0/19
no ip address
!
interface FastEthernet0/20
no ip address
!
interface FastEthernet0/21
no ip address
!
interface FastEthernet0/22
no ip address
!
interface FastEthernet0/23
switchport access vlan 2
switchport mode access
no ip address
!
interface FastEthernet0/24
no ip address
!
interface GigabitEthernet0/1
switchport mode trunk
no ip address
!
interface GigabitEthernet0/2
no ip address
!
interface Vlan1
ip address 10.166.246.91 255.255.255.0
no ip route-cache
!
ip http server
!
!
line con 0
line vty 0 4
password C2950TELNET
login
line vty 5 15
password C2950TELNET
login
!
end

C2950-SW1#
C2950-SW1#SHOW VLAN

VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
Fa0/5, Fa0/6, Fa0/7, Fa0/8
Fa0/9, Fa0/10, Fa0/11, Fa0/12
Fa0/13, Fa0/14, Fa0/15, Fa0/16
Fa0/17, Fa0/18, Fa0/19, Fa0/20
Fa0/21, Fa0/22, Fa0/24
2 SDS-2 active Fa0/23
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active

VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1 enet 100001 1500 - - - - - 0 0
2 enet 100002 1500 - - - - - 0 0
1002 fddi 101002 1500 - - - - - 0 0
1003 tr 101003 1500 - - - - - 0 0
1004 fdnet 101004 1500 - - - ieee - 0 0
1005 trnet 101005 1500 - - - ibm - 0 0

Remote SPAN VLANs
------------------------------------------------------------------------------


Primary Secondary Type Ports
------- --------- ----------------- ------------------------------------------

The 3COM doesn't have a printable config that I could find. I programmed ports 23 & 24 for VLAN2 and port 26 as the UPLINK as 3COM calls it. Since it did work before I unplugged it.

Any help is apppreciated!

....JIM....

 

[SYQUEST]

I finally got it to work. In the 3COM I removed the VLAN, then added it back. That seemed to work, but if there was a reset or power failure (both switches do have UPS) would it comeback to life by itself?

I'll try starting a thread on the 3COM Forum and see what responses I get.

....JIM....