Trunking between 9500 and 3750X switch not working

[NetEng20k]

I have a weird issue. Im trying to trunk a 9500 and 3750X switch and although the ports show as connected, they cant ping each other. The 3750 does require the encap dot1q command while the 9500 doesn't and also the 3750 is using a 10gb sfp port while the 9500 is using a 20gb sfp port. Could any of those 2 be the reason for the failure?

Here is the config from the 3750:

switchport trunk encapsulation dot1q
switchport trunk allowed vlan 5,7,20
switchport mode trunk

Here's the config from the 9500:

switchport trunk allowed vlan 5,7,20
switchport mode trunk
channel-group 7 mode active
end

Any ideas would be much appreciated!

[MHM Cisco World]

channel-group 7 mode active <<- trunk port I understand but PortChannel, I dont understand 

both side must run PO or both side must not run PO. 
here one side run PO other not and hence the trunk is not work

[balaji.bandi · Accepted solution]

First you need to clarify, is the trunk you building is with more  ports  or only with 1 port ?

If only 1 Interface in the trunk then you do not need channel-group config on Cat 9500

if ports - then you need to create channel group to bundle the interface config on Cat 3750

As long as you have used both the side comptable optic exmaple 10G-SR both the side, that should work.

you also need to provide the config on the interface applied.

 they cant ping each other.  - what vlan they belong to what is each side IP address you trying to ping.

[paul driver]

Hello
The trunk connection between the two switch are different, the 9k is in a LACP port channel and the 3750x is a single trunk, Also confirm the L3 interface/SVI on both switchs are showing up?

[Leo Laohoo]

What firmware is the 9500 running on?

[mlund]

As already pointed out, we need more information to figure out why you can't ping. But to answer your question, 3750 is an old switch that can use both dot1q and isl ( cisco proprierty protocol ), that is why you need to specify which of them to use. 9500 can only do dot1q, so this is on by default when you enable trunk. When using different port types, the important thing is to use same type of sfp. If the port state is up then there should be connectivity. You can use "show cdp neighbor" to see if there is traffic going over the link.

[NetEng20k]

as it turns out, the vlans were different on one side of the trunks. thank you all!