Sunday , March 25 2018
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basic QinQ configuration on Huawei switches

In traditional 802.1Q protocol, service provider should assign different VLAN IDs to users of different VLANs. The numer of VLANs is limited to 4094 IDs. In addition, different users cannot use the same VLAN ID.

A simple method to solve this is to implement QinQ. The QinQ technology improves the utilization of VLANs by adding another 802.1Q tag to a packet with an 802.1Q tag. In this manner, services from the private VLAN can be transparently transmitted through the public network. The ISP network only provides one VLAN ID for different VLANs from the same user network. This saves VLAN IDs of an ISP. Meanwhile, the QinQ provides a simple Layer 2 VPN solution to a small MAN or a local area networks.

QinQ tunneling on Huawei switches

Let’s assume that we have two enteprise networks. Each enterprise has two branch offices, located in different cities. As an ISP, we cannot force these enterprises to use different VLAN planning. In our case, both use VLAN 10 and our task is to transparently transmitt traffic, through ISP network, between remote offices.

What we want to achieve is to ensure communication between remote offices of each enterprise and to block communication between Enterprise_1 and Enterprise_2. We can use basic QinQ tunneling in this case. It adds the same outer VLAN tag to all the frames entering a Layer 2 port.

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port security on Huawei switches

How to prevent unauthorized users from connecting their PCs to an enterprise network? How to prevent employees from connecting unauthorized devices to a LAN or moving their computers without permission?

Port Security is a Layer 2 feature, which can be enabled on an interface, to prevent devices with untrusted MAC address, from accessing a switch interface. When enabled, MAC address of the device connected to the port, is dynamically learned by the switch and stored in a memory (by default it is not aged out). Only this MAC address is then allowed to forward traffic over switch port (only one trusted MAC is allowed by default). Every different MAC address will cause the port to go into one of the following states:

  • Protect – packets coming from untrusted MAC address will be dropped,
  • Restrict – packets coming from untrusted MAC address will be dropped and SNMP trap message will be generated (default behavior),
  • Shutdown – port will be put into shutdown state.

Let’s configure  port security feature on a switch port and see, how it works.

Enter system view, return user view with Ctrl+Z.
[labnarioSW1]interface gi0/0/1
[labnarioSW1-GigabitEthernet0/0/1]port link-type access
[labnarioSW1-GigabitEthernet0/0/1]port-security enable

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Link Flapping Protection on Huawei switches

I have come across link flapping protection feature recently. It is available on S5700 switches. It looks like it is a new feature on Huawei switches. I had not met it in older hardware versions. That’s why I decided to write a few words about it. Unfortunatelly, although this command is available in Huawei network simulator eNSP, it does not work properly. But maybe you will have possibility check it on your real devices.

Port flapping (port going UP and DOWN continually) can be caused by a faulty cable, link failure, active/standby switchover, port hardware failure, etc. Frequent status changes on an interface can lead to:

  • STP topology recalculation and changes,
  • ARP entries updates,
  • dynamic routing instability and convergence problems.

All these issues can negatively affect switch performance and should be avoided.

Link Flapping Protection is a feature that can be implemented on an interface to solve problems caused by the flapping port or link. It checks the interface flapping frequency and link flapping detection interval. If the number of interface flapping times reaches the limit, in a specified period, the interface is shut down.

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error-down auto-recovery on Huawei switches

Some of you may know Cisco’s err-disable recovery feature, which allows to automatically bring a port from err-disable back to UP state. Huawei switches have similar functionality, which is called error-down auto-recovery.

There are five reasons a port can enter into error-down state:

  • BPDU protection
  • EFM threshold
  • EFM remote failure
  • Auto defend
  • Link flapping
  • MAC address flapping

Let’s take a look, how this feature works, in a network running STP, when BPDU protection is the reason that a port goes into DOWN state. If you are not familiar with BPDU protection feature, read my previous article “Protecting STP on Huawei switches”.

I have configured STP BPDU protection on the Ethernet 0/0/1 interface of labnarioSW1 switch as follows:

[labnarioSW1]int e0/0/1
[labnarioSW1-Ethernet0/0/1]stp edged-port enable
[labnarioSW1]stp bpdu-protection

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protecting STP on Huawei switches

As a continuation of the STP Root Protection feature I want to describe additional STP protection functions and show you, where these functions should be implemented, in a typical campus LAN environment.

BPDU Protection feature can be used to protect switches against STP BPDU attacks. It should be implemented on every switch, which has ports directly connected to end-user workstations. This is because we do not expect receiving STP BPDU from user workstations. When STP BPDUs are received on the edge port, STP topology recalculation occurs, causing network flapping. If the port is configured with BPDU Protection and the switching device receives STP BPDUs, then the port is placed into shutdown state, protecting STP topology from recalculation. By default BPDU Protection feature is disabled on Huawei switches. To enable it:

[labnario_sw]interface Ethernet 0/0/1
[labnario_sw-Ethernet0/0/1]stp edged-port enable 
[labnario_sw]stp bpdu-protection

When a switch port is configured as a STP Edged and STP BPDU is received, the port is placed into shutdown state:

May 13 2013 20:17:00-08:00 labnario_sw%%01MSTP/4/BPDU_PROTECTION(l)[4]:This edged-port Ethernet0/0/1 that enabled BPDU-Protection will be shutdown, because it received BPDU packet!
[labnario_sw-Ethernet0/0/1]dis cur int e0/0/1
interface Ethernet0/0/1
 stp edged-port enable

[labnario_sw-Ethernet0/0/1]dis int eth0/0/1
Ethernet0/0/1 current state : Administratively DOWN
Line protocol current state : DOWN

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