vlan, trunking problem?!

[Endwigast]

Hi,

We have 3 switch stacks connected via ethernetcable. The switches in the stack are connected via gigastack. We have 4 vlans. The ports connecting each stack, the gigaports connecting each switch in the stack and the port connected to the router is configured as a trunk port and allows all vlan. All switches are running as transparent. The port on the router is configured as such:

interface f1/1.1

encapsulation dot1q 1

ip address 10.10.1.254 255.255.255.0

interface f1/1.2

encapsulation dot1q 2

ip address 10.10.2.254 255.255.255.0

interface f1/1.3

encapsulation dot1q 3

ip address 10.10.3.254 255.255.255.0

interface f1/1.4

encapsulation dot1q 4

ip address 10.10.4.254 255.255.255.0

switch port trunk config:

interface f0/?

switchport mode trunk

giga port config

interface g0/?

switchport mode trunk

why is it that when I assign some ports on the left side of the stack to vlan 4 and connect a pc to it then assign a static ip I can't ping the gateway?

Am I missing something? Thanks.

diagram:

__ __ __

__--__--__--R

__ __ __

__ __ __

[milan.kulik]

Hi,

a) which VLAN is antiv on the trunk?

If VLAN1 (default) you should configure

interface f1/1.1

encapsulation dot1q 1 native

on your router.

b) What is the switch type? Some switches are using ISL as default.

Check it with sh int g0/? switchport

and if ISL is used, configure

interface g0/?

switchport trunk encapsulation dot1q

HTH,

Milan

[Endwigast]

Hi,

a) what trunk? here is the output of the 3rd and 4th switch on the left stack. all trunk ports are located at the 1st switch. the configuration on interface 1/1.1 already has native in it. vlans 3 and 4 work on all the switches.

switch3#sh int g0/1 trunk

Port Mode Encapsulation Status Native vlan

Gi0/1 on 802.1q trunking 1

Port Vlans allowed on trunk

Gi0/1 1-4094

Port Vlans allowed and active in management domain

Gi0/1 1

Port Vlans in spanning tree forwarding state and not pruned

Gi0/1 1

switch4#sh int g0/1 trunk

Port Mode Encapsulation Status Native vlan

Gi0/1 on 802.1q trunking 1

Port Vlans allowed on trunk

Gi0/1 1-4094

Port Vlans allowed and active in management domain

Gi0/1 1,2,3,4

Port Vlans in spanning tree forwarding state and not pruned

Gi0/1 1,2,3,4

for some reason vlans 3 and 4 work but not 2.

here is the output from the ethernet port connected to the middle switch stack.

switch1#sh int f0/1 trunk

Port Mode Encapsulation Status Native vlan

Fa0/1 on 802.1q trunking 1

Port Vlans allowed on trunk

Fa0/1 1-4094

Port Vlans allowed and active in management domain

Fa0/1 1,2,3,4

Port Vlans in spanning tree forwarding state and not pruned

Fa0/1 1,2,3,4

b) we're using 2950-48 emi. switch ports are autonegotiate.

thanks

[milan.kulik]

I meant the trunk between the switch and the router.

You need to configure the native VLAN subinterface on the router.

The router also doesn't negotiate the trunk, you need to configure nonegotiation on the switch side

(i.e. switchport trunk encapsutation dot1q) generally, but 2950 supports 802.1q only, so it's not necessary in this case.

BTW, your topology diagram is not clear to me.

But still you should be able to Ping between two PCs inside VLAN4.

What happens if you connect two PCs to VLAN4 on the same switch and try to Ping between them?

And if you connect the second PC to another switch in the same stack?

And if you connect the second PC to a switch in another stack?

If all these Pings work fine, the problem is definitely in the configuration of the trunk between your router and switch.

Regards,

Milan