Hello: We are going to have the following (simplified scenario): - vlans 101,102 are going to have servers. - vlan 101 uses 10.101.101.0/24 addressing and vlan 102 uses 10.102.102.0/24 addressing. - vlans 101 and 102 doesn't have level 3. - vlans 201,202 are going to have the level3 interfaces corresponding to vlans 101 and 102 respectively, so vlan201 will have the "interface vlan 201" defined as 10.101.101.1/24 and vlan202 will have the "interface vlan 202" defined as 10.102.102.1/24 At this point, if we do not any more things, servers from vlan101 or vlan102 will not be able to reach their default gateway because the default gateway is in another vlan. OK, Then we get two devices (IPS1 & IPS2), each of them having two interfaces. IPS1,interface 1 is connected to switch1 port 1/1. IPS1,interface 2 is connected to switch2 port 2/1. IPS2,interface 1 is connected to switch1 port 1/2. IPS2,interface 2 is connected to switch2 port 2/2. switch1,port 1/1 is a trunk with allowed vlans 101,102. switch1,port 1/2 is a trunk with allowed vlans 101,102. switch2,port 2/1 is a trunk with allowed vlans 201,202. switch2,port 2/2 is a trunk with allowed vlans 201,202. IPS1 will have the following config: Traffic entering interface 1 must be forwarded to interface 2 with the following vlan translations: original_vlan 101 is translated_to_vlan 201 original_vlan 102 is translated_to_vlan 202 Traffic entering interface 2 must be forwarded to interface 1 with the following vlan translations: original_vlan 201 is translated_to_vlan 101 original_vlan 202 is translated_to_vlan 102 Exactly the same config to IPS2. My question is if this is a valid configuration from the spanning-tree point of view, I ask this because we translate de vlan tags and we are thinking that this can affect the correct operation of stp. In other words... with this config will we have a loop or stp will operate OK and put one port (1/1,1/2,2/1 or 2/2) as blocking? Keep in mind that doing an etherchannel between 1/1 and 2/1 and another etherchannel between 2/1 and 2/2 is not an option in this case (remember the explanation is a "simplified scenario" :-) the real one is a lot bigger and is nor possible for us to make the etherchannels). Thanks a lot and best regards