Publication Date: 2018-02-28 | Views: 819 | Downloads: 0 | Author: c84079748 | Document ID: EKB1001358434
Customer have the topology below with STP disabled. The switches are S5720-52X-PWR-LI-AC model with version V200R010C00SPC600 On top of this topology with stp disabled, he configured loopback-detect function for all interfaces except interfaces GigabitEthernet 0/0/17 and 0/0/18 which are added in Eth-Trunk 1 interface for both E2 and E3. Switch E1 is a HP switch with loopback-detect function enabled also on his Bridge-Aggregation interfaces.
After connecting by mistake, switch E2 interface GigabitEthernet 0/0/4 with switch E3 interface GigabitEthernet 0/0/9, a loop was created at layer two.
E2 interface:
#
interface
GigabitEthernet0/0/4
port link-type access
port default vlan 168
loopback-detect packet vlan 168
loopback-detect enable
#
E3 interface
#
interface
GigabitEthernet0/0/9
port link-type access
port default vlan 168
loopback-detect packet vlan 168
loopback-detect enable
#
Customer reported this
incident and asked why is this possible since the two interfaces were working
in loopback-detect mechanism.
Apparently the loopback-detect function does not work over Eth-Trunk
interfaces. We have tried also to enable loopback-detect on physical interfaces
that are added to aggregation interface but, as soon as the interfaces are
added to Eth-Trunk, the command does not work anymore.
The conclusion is that the function is not supported over Eth-Trunk
interfaces.