My name is Zanclair Ferrari Junior, I am an N3 consultant at Made4it. On a daily basis, we implement, solve problems and carry out actions in OLTs in order to improve performance and guarantee greater security for internet providers. Thinking about it, we brought 3 good practice tips that should be implemented in all internet providers in the part of OLTs.
Let’s see what the tips are and why we consider these actions essential for internet providers.
1- Remove the PVID from the switch interface that serves the OLT
When we activate an OLT in the network, we usually connect it to a switch, and in the interface we pass the VLANs we need in trunk (tagged), but we forget the PVID (Port VLAN ID) of the interface, which is the VLAN that the switch has to tag a VLAN tag in frames that do not have one (understand that for the switch, internally, every frame has a VLAN, whether it comes externally or not) and that by default it is VLAN 1.
Now imagine the scenario in which, for some reason, the OLT “leaks” the communication traffic it has with the ONUs internally through its uplink, through its PVID, the switch receives this, as it is without a VLAN tag, it marks it with PVID VLAN and passes forward through the PVID VLAN to another OLT, which is also leaking its internal communication traffic with the ONUs through the uplink, believe me, this is common, which causes several anomalies, such as internal looping, ONUs flapping, and several other abnormal behaviors, so for good practice, if it is connected to a switch, it is interesting to remove this PVID from the switch interface with the OLT, so as not to leak unwanted traffic. For each switch this configuration is different.
2- Disable the STP of the switch interface that serves the OLT
By default, in most manufacturers, the STP (Spanning Tree Protocol) is enabled on the switch interfaces, as there is a reason for this, to avoid looping in the network, but thinking about a connection with OLT, if the BPDU of the STP of some ONU /client go up and pass through the OLT uplink and reach the switch, as STP is enabled on the interface, it will be negotiated.
Now imagine if, for some reason, the exchanged STP decides that the interface with the OLT is a backup and disables it, consequently stopping the whole OLT, or that the client is the root bridge, affecting all the STP in the network, it is a very big risk, believe me, this is common.
There are even some OLT manufacturers, such as Huawei, who block this STP BPDU by default coming from the ONU to the uplink, but other manufacturers do not have this feature, which can cause serious problems there, so as a good practice, disable the STP on the switch interface with the OLT.
3- Daily Autosave (Automatic Backup)
When we make a change in the configuration of an OLT, we have to save (persist the configuration) in it at some point, otherwise the information will be lost if it restarts or has a problem, but the useful life of this memory is limited in the number of times it can be be written, that is, if we save every moment that activates or removes an ONU, doing this 30x a day, it is decreasing its useful life drastically, so the life time of the OLT will be smaller, since, generally, it is not possible change this memory easily.
As a matter of good practice, we use “autosave”, the name can vary for each manufacturer, but it is a function that you can define a time, for example at 7 pm every day, for the OLT to automatically save the changes made, that is, if for some reason the OLT restarts, the most that can happen is losing the day’s modifications, and with that we guarantee that the memory will last longer.
If you still have any questions about OLT or are looking for some ISP deployment and support work, please contact our team.
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Zanclair Ferrari Junior | Network Consultant
JNCIS-SP | CCNA | HCIA | MTCRE
