Trunk between 3650 and 3560

failingrw · ‎09-28-2017

I have two 3560s that are trunked together with five vlans allowed. Each vlan is assigned an IP address. Ping works between the two 3560s for each vlan. There is an identical setup for two 3650s and ping works. But if the trunk is between a 3560 and a 3650 ping does not work. What am I missing?

3560 config

interface GigabitEthernet0/23
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 100,110,200,210,700
switchport mode trunk
!
interface GigabitEthernet0/24
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 100,110,200,210,700
switchport mode trunk
!

interface Vlan100
ip address 10.0.0.1 255.255.255.128
!
interface Vlan110
ip address 10.50.0.1 255.255.255.128
!
interface Vlan200
ip address 10.10.0.1 255.255.255.128
!
interface Vlan210
ip address 10.60.0.1 255.255.255.128
!
interface Vlan700
ip address 10.80.0.1 255.255.255.224

3650 config

interface GigabitEthernet1/0/23
switchport trunk allowed vlan 100,110,200,210,700
switchport mode trunk
!
interface GigabitEthernet1/0/24
switchport trunk allowed vlan 100,110,200,210,700
switchport mode trunk

The vlan section is the same for all devices

RyanB · ‎09-28-2017

Have you confirmed that the trunk is even up?
Is layer 2 traffic passing or is it just an issue with layer 3?
What speeds and duplex have your interfaces negotiated at?

Meheretab Mengistu · ‎09-28-2017

You will also need to check the status and speed of the trunk ports. If the trunk ports are in up/up state, please share the output of the following commands:
show int trunk
show run | inc spanning-tree
show int status | ex notconnect
show run int gi1/x/x (trunk port interfaces)
show int gix/x/x (trunk port)

HTH,
Meheretab

HTH,
Meheretab

Derrick Hurley · ‎09-29-2017

Do you have an access port in the up state in each of those VLANs on either of the switches? If you don't have a device active in the VLAN the SVI won't be up, and therefore, not pingable.

Check to see if your protocol is up on the VLANs. If protocol is down, then try assigning a port to one of the vlans (switchport access vlan ##) and connect a device to it.

DS1-0694-M1#show ip int brief | in Vlan
Interface              IP-Address      OK? Method Status                Protocol
Vlan1                  unassigned      YES NVRAM  administratively down down
Vlan10                 10.1.1.1        YES NVRAM  up                    up
Vlan100                10.1.2.1        YES NVRAM  up                    up

failingrw · ‎10-03-2017

Finally figured it out thanks to everyones suggestions on what to look at. First I must apologize since the posted configurations worked. It is when a port-channel was added to make the two connections act at one that it lost connectivity. The additional configuration is:

interface port-channel 1

switchport trunk encapsulation dot1q ! this is only on the 3560

switchport trunk native vlan 98

switchport trunk allowed vlan 10,11,20,21,70

switchport mode trunk

Ports 23 and 24 for both 3560 and 3650 had the following line added

channel-group 1 mode desirable

If two 3560s were used or two 3650s there was no issues and connectivity was as it should be. The problem arose when one 3560 was used and one 3650. Then there was no connectivity. The solution was to put one device in auto negotiate mode by removing "switchport mode trunk" from port-channel 1, gig 0/23 and gig 0/24.

I found the command "show int trunk" the most useful in debugging this problem. It showed if the trunk even existed or not.

If this is a little vague to you, it is intentional sort-of. The setup is in a classified area and it is painful to get data in and out of it. Sorry. I can try to explain better if anyone needs it.