09-18-2009 05:49 AM - edited 03-04-2019 06:05 AM
Hello,
I have this situation:
SWITCH1---SWITCH2---ROUTER
SWITCH1 port toward SWITCH2 has configuration:
Interface GigabitEthernet1/0/1
switchport access vlan 333
switchport mode dot1q-tunnel
l2protocol-tunnel cdp
l2protocol-tunnel stp
l2protocol-tunnel vtp
SWITCH2 port toward ROUTER has configuration:
Interface GigabitEthernet 1/0/2
switchport access vlan 222
switchport mode dot1q-tunnel
l2protocol-tunnel cdp
l2protocol-tunnel stp
l2protocol-tunnel vtp
When ROUTER connects to SWITCH2
with interface configuration:
Interface GigabitEthernet0/1.10
encapsulation dot1q 10
ip address 10.0.0.1 255.255.255.0
then port on SWITCH1 goes to error disable state:
%PM-4-ERR_DISABLE: l2ptguard error detected on Gi1/0/1, putting Gi1/0/1 in err-disable state.
Everything works only when l2ptprotocol commands are removed either from SWITCH1 or SWITCH2.
Can anyone give me explanation for this behavior.
Thanks in advance,
A
09-18-2009 06:28 AM
Hi Antonio,
It's an expected behavior as switch 1 detects a Loop condition:
"
If an encapsulated PDU (with the proprietary destination MAC address) is received from a tunnel port or access port with Layer 2 tunneling enabled, the tunnel port is shut down to prevent loops.
"
You can't tunnel twice those protocols. It's not supported.
HTH
Laurent.
09-18-2009 07:35 AM
thanks Laurent.
A
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