Trunking VLANs for switches

Unanswered Question
Feb 16th, 2008

I have 3 switches, (1)3550 and (2) 2960's, each one is 48 ports. I'm using the 3550's port F0/1 for routing, all the other ports have a VLAN tied to them.

3550 = swA

2960 = swB

2960 = swC

swA = (4) VLANs (Servers, Printers, Office, IT)

swB = (2) VLANs (Sales & Marketing)

swC = (3) VLANs (WIFI, Pub Access, Service)

Trunking ports

swA gi0/2 to swB gi0/1

swB gi0/2 to swC gi0/1

Right now I have all VLANs being trunked acrossed all trunk ports

For trunking purposes on swA, do I need to trunk its VLANs to the other switches? And the same with swB's VLANs being trunked to swC.

I'm thinking that I dont have to because if a VLAN needs access to another VLAN it is going to the routing for where to go. Like router on a stick. But if I have printers on swC I would then need a trunk for it to let the switch know where the other port is located.

This is what I'm thinking it should be.

Trunking ports

swA gi0/2 to swB gi0/1 (Sales, Marketing, WIFI, Pub Access, Service)

swB gi0/2 to swC gi0/1 (WIFI, Pub Access, Service)

I have this problem too.
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Edison Ortiz Sat, 02/16/2008 - 08:26

There is something I don't understand from your setup.

The 3550 is the only Layer3 switch that you have mentioned.

The other Layer2 switches contain Vlans not contained in the 3550, those Vlans are Sales, Marketing, WIFI, Pub Access and Service.

How those Vlans communicate at Layer3? You mentioned this:

if a VLAN needs access to another VLAN it is going to the routing for where to go.

Where is the router other than the 3550?

If you have an external router for inter-vlan routing, what's the point of having the 3550 switch? The 3550 will provide a faster inter-vlan routing than any 'router-in-a-stick' configuration out there.

Also, please post configs along with a network diagram so we can get a clear picture of your network.

___

Edison.

jmaurer1205 Sat, 02/16/2008 - 16:12

hostname 3550-swA

!

ip subnet-zero

ip routing

!

spanning-tree mode pvst

spanning-tree extend system-id

spanning-tree vlan WIFI,Sales,Service01,Marketing,Service02 priority 8192

spanning-tree vlan SvrGp01,Printers,Office,SvrGp02,IT priority 4096

!

interface FastEthernet0/1

no switchport

ip address 10.5.15.2 255.255.255.252

speed 100

duplex full

!

interface FastEthernet0/2 - 8

switchport access vlan SvrGp01

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/9 - 20

switchport access vlan SvrGp02

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/21 - 30

switchport access vlan Printers

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/31 - 42

switchport access vlan Office

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/43 - 46

switchport access vlan IT

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/47 - 48

switchport mode dynamic desirable

!

interface GigabitEthernet0/1

switchport access vlan SvrGp02

switchport mode access

!

interface GigabitEthernet0/2

switchport trunk encapsulation dot1q

switchport trunk native vlan Native

switchport trunk allowed vlan 1,WIFI,SvrGp02,Printers,Office,Sales,Service01,Marketing,SvrGp01,Service02,IT,Native

switchport mode trunk

switchport nonegotiate

!

interface Vlan1

no ip address

shutdown

!

interface Vlan SvrGp02

ip address 10.12.10.14 255.255.255.240

!

interface Vlan Printers

ip address 10.12.10.30 255.255.255.240

!

interface Vlan Office

ip address 10.12.10.62 255.255.255.224

ip helper-address 10.12.10.1

!

interface Vlan Sales

ip address 10.12.10.94 255.255.255.224

ip helper-address 10.12.10.1

!

interface Vlan Service01

ip address 10.12.10.126 255.255.255.224

ip helper-address 10.12.10.1

!

interface Vlan Marketing

ip address 10.12.10.190 255.255.255.192

ip helper-address 10.12.10.1

!

interface Vlan SvrGp01

ip address 192.168.1.1 255.255.255.240

!

interface Vlan Service02

ip address 10.12.8.206 255.255.255.240

ip helper-address 10.12.10.1

!

interface Vlan Public

ip address 10.12.10.33 255.255.255.224

!

interface Vlan WIFI

ip address 10.10.10.33 255.255.255.224

!

interface Vlan IT

ip address 10.11.201.14 255.255.255.240

!

ip classless

ip http server

I have the VLANs on the 3550, which is the L3 SW. I probly should have stated that at the beginning. I tried to clean up the config, so I hope I didnt mess it up to much.

jmaurer1205 Sat, 02/16/2008 - 16:13

swB

hostname 2960-swB

!

spanning-tree mode pvst

spanning-tree extend system-id

spanning-tree vlan Sales,Marketing priority 4096

!

vlan internal allocation policy ascending

!

interface FastEthernet0/1 - 30

switchport access vlan Marketing

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/31 - 48

switchport access vlan Sales

switchport mode access

spanning-tree portfast

!

interface GigabitEthernet0/1

switchport trunk native vlan Native

switchport trunk allowed vlan 1,WIFI,SvrGp02,Printers,Office,Sales,Service01,Marketing,SvrGp01,Service02,IT,Native

switchport mode trunk

switchport nonegotiate

speed 1000

duplex full

!

interface GigabitEthernet0/2

switchport trunk native vlan 301

switchport trunk allowed vlan 1,WIFI,SvrGp02,Printers,Office,Sales,Service01,Marketing,SvrGp01,Service02,IT,Native

switchport mode trunk

switchport nonegotiate

speed 1000

duplex full

!

interface Vlan1

no ip address

no ip route-cache

shutdown

swC

hostname 2960-swC

!

spanning-tree mode pvst

spanning-tree extend system-id

spanning-tree vlan WIFI,Service01,Service02 priority 4096

!

vlan internal allocation policy ascending

!

interface FastEthernet0/1 - 16

switchport access vlan Service01

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/17 - 24

switchport access vlan Service02

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/25 - 34

switchport access vlan WIFI

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/35 - 48

!

interface GigabitEthernet0/1

switchport trunk native vlan Native

switchport trunk allowed vlan 1,WIFI,SvrGp02,Printers,Office,Sales,Service01,Marketing,SvrGp01,Service02,IT,Native

switchport mode trunk

switchport nonegotiate

speed 1000

duplex full

!

interface GigabitEthernet0/2

shutdown

speed 1000

duplex full

!

interface Vlan1

no ip address

no ip route-cache

shutdown

Edison Ortiz Sat, 02/16/2008 - 16:22

I checked your config I wouldn't be too concerned about your trunking configuration (not sure why you are). If you want to limit the Vlans allowed in the trunk, just enable VTP Pruning in the domain - is that simple.

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_4_2/config/vlans.htm#xtocid79807

As for changing inter-switch links from trunk mode to access mode, what benefit are you getting from it?

HTH,

__

Edison.

jmaurer1205 Sun, 02/17/2008 - 09:44

I don't have it installed yet. This is my first Cisco network that I'm making from scratch and want the implementation to go smooth, plus getting servers in to. When I first started we had only 9 computer with 13 terminals and now we have over 70 computers and I'm trying to manage the network with servers instead of individual attention. Being the only IT personel there, it will be a long weekend for the conversion.

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