2950 trunked to 3560 but not communication

[volleyman]

I have created trunk ports on a 2950 and 3560. they are both set for native vlan 999. I can see CDP information across them.

Also, the Show Interface trunk command shows that the trunk is good.

but client is not getting dhcp and when I try to ping from the 2950 to the 3560 I don't get anything. 3560 is up and working on the network, 2950 is the new addition and its not working.

what am I missing?



Zane D.
Systems Admin

 

[baddos]

Can you post show interface num/num switchport of both switches?

 

[volleyman]

2950:

interface FastEthernet0/1
description **** trunk to 3560-02 ****
switchport trunk native vlan 999
switchport mode trunk
no ip address
duplex full
speed 100
spanning-tree portfast


3560:

interface GigabitEthernet0/1
description **** Uplink to Maryland-2851-01 g0/0 ****
switchport trunk encapsulation dot1q
switchport trunk native vlan 999
switchport mode trunk



Zane D.
Systems Admin

 

[baddos]

Thats a sample of the config. I'm looking for the "show interface NUM/NUM switchport".

It would look something like this:

show interface fa0/1 switchport
Name: Fa0/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 1 (VLAN NAME)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL

Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

 

[vipergg]

Did you actually create the layer 2 vlans on the new switch and the 3560 if this is a new vlan ? If you do a "show vlan " do all you vlans show active ?

 

[clarktuba]

Taking a quick look at your config, the 2950 doesn't have an encapsulation for the trunk. If my memory serves me, the default for the 2950 is ISL and the 3560 you have set to dot1q. Try setting the encapuslation on the 2950 to dot1q and see what happens.

 

[vipergg]

The 2950 only supports dot1q and does not show because it is the default. You could try setting the trunk mode as " desirable on both ends and see if it comes up . That is the trouble with forcing it on it can say trunking but it may not be working as you have seen , if it negotiates the trunk "desirable" it will create the trunk only if the paramters are the same. If it does not create the trunk it may give you a reason why in the logs and you can work off of that . Something easy to try, "switchport mode dynamic desirable".

 

[vipergg]

Just by looking at your config , on the 3560 you did not hardcode the speed and duplex so if its left as auto then you have a speed/duplex mismatch because the 3560 would default to 100 /half this may cause a problem when creating a trunk.

 

[Cluebird]

You have a native Vlan mismatch. Specify the same native vlan on the trunks and it'll work.

 

[Cluebird]

Disregard previous post. I CAN'T READ MONDAYS!!!!

 

[Viconsul]

How are you connecting the two switches together?
The connection btw the two needs to be a crossover.
Worth a check.