I am configuring a new Cisco edge switch stack, and temporarily I am trunking this stack through another edge switch back to my core switch (no spare fiber pairs to use to trunk directly). This is how they're configured (lots of extraneous stuff removed):
**2960X Edge Stack**
vtp mode transparent
vlan 10 (old data subnet, 10.1.10.0/24)
vlan 1000 (management subnet, 10.255.10.0/24)
vlan 1080 (new data subnet, 10.1.80.0/24)
int gi1/0/48 (trunk to 3560 edge switch)
switchport mode trunk
switchport trunk native vlan 1000
switchport trunk allowed vlan 10,1000,1080
spanning-tree portfast network
int gi3/0/30 (edge port)
switchport mode access
switchport access vlan 1080
spanning-tree portfast edge
ip routing
ip route 0.0.0.0 0.0.0.0 10.255.10.254
**3560 Edge Switch**
vtp mode transparent
vlan 10
vlan 1000
vlan 1080
int gi0/3 (edge port)
switchport mode access
switchport access vlan 1080
spanning-tree portfast
int gi0/20 (trunk to 2960 edge stack)
switchport mode trunk
switchport trunk encapsulation dot1q
switchport trunk native vlan 1000
switchport trunk allowed vlan 10,1000,1080
spanning-tree portfast
int gi0/49 (trunk to 9300 core switch)
switchport mode trunk
switchport trunk encapsulation dot1q
switchport trunk native vlan 1000
switchport trunk allowed vlan 10,1000,1080
spanning-tree portfast
ip routing
ip route 0.0.0.0 0.0.0.0 10.255.10.254
**9300 Core Switch**
vtp mode transparent
vlan 10
vlan 100 (server subnet, 10.1.0.0/24)
vlan 1000
vlan 1080
int te1/1/2 (trunk to 3560 edge switch)
switchport mode trunk
switchport trunk native vlan 1000
switchport trunk allowed vlan 10,1000,1080
int Vlan10
ip address 10.1.10.254 255.255.255.0
ip helper-address 10.1.0.1
int Vlan100
ip address 10.1.0.254 255.255.255.0
int Vlan1000
ip address 10.255.10.254 255.255.255.0
int Vlan1080
ip address 10.1.80.254 255.255.255.0
ip helper-address 10.1.0.1
ip routing
A device connected to an edge port on the 2960X in VLAN1080 (gi3/0/30 in this case) cannot get a DHCP address, and even with a statically-assigned address can't ping the gateway (10.1.80.254). If I put that port in VLAN10 instead, it will get a DHCP address and can ping everything as expected.
A device connected to an edge port on the 3560 in VLAN1080 will get a DHCP address in the correct scope (10.1.80.0/24) and can ping the gateway (10.1.80.254).
What seems to be happening is that the 3560 is maybe stripping the 802.1Q tags when traffic is traversing from the 2960X to the 9300, but I don't see any reason it should be doing that. Can anyone suggest what's happening here and how to fix it?
