Labnario Huawei From Scratch

BFD (Bidirectional Forwarding Detection)

What to do to quickly establish an alternative path in case of communication failure between adjacent systems?

There are two detection mechanisms:

• Hardware detection, for example alarms in SDH used to detect link faults
• Hello mechanism used by routing protocols.

The main disadvantage of hardware detection is that not all media support it. For example Ethernet does not provide this kind of signalling.

When there is no hardware signalling we can use Hello in routing protocols but this mechanism is relatively slow. Sensitive services, for example voice, cannot work with more than one second delay.

The best solution is to use BFD (Bidirectional Forwarding Detection). This is simple mechanism that works independently of media, data and routing protocols. The main goal of BFD is to detect failures in the path between adjacent devices in a short time (minimum detection time for NE40E is 30ms). It does not matter if it is physical link, virtual circuit, tunnel, MPLS LSP, multi-hop path or unidirectional link. We can treat BFD as a simple Hello protocol where a pair of devices periodically sends BFD packets between them. If one device does not receive BFD packets within specified period, the system assumes that the bidirectional path to the neighboring system has failed.

There are two interface backup modes:

1. Active/standby
2. Load balancing

In common active/standby mode only one interface transmit services at any time. When active interface works properly, it transmit all the traffic. In case of fault of the primary interface, a backup interface with the highest priority starts transmitting packets. If primary interface recovers, traffic is switched back to active interface.

In load balancing mode, in case traffic volume exceeds an upper threshold set for active interface, a backup interface with the highest priority starts transmitting packets and load balancing is performed.

Which mode we have is determined by upper and lower thresholds. If thresholds are not set, active/standby mode is used. Otherwise, load balancing mode is used.

Let’s assume that we have the following topology:

display elabel [ backplane | slot-id ]

Using this command lets you to display electronic labels of the boards installed. If you do not specify slot-id you will see information about all the boards. An output of this command includes among others:

• type of boards and PIC cards
• bar code
• English description
• BOM
• vendor’s name.

As you already know you can assign a different privilege level for each user, configured on a Huawei device. How to configure local user and how to access Huawei device you can read in one of my previous posts.

user privilege level

Today I want to focus on the privilege level of local user. Each year lots of accidents in IP networks are caused by inexperienced employees. We can decrease the number of such accidents setting privilege level for local users, logging into network devices. Setting a lower privilege level for such employees increases networks’ safety. For more experienced engineers  we can either configure higher privilege level or set a super password, to let them to perform advanced operation.

Let’s assume that we have created a local user with the lowest priority:

#
local-user labnario password cipher &EU15O"Q3/;Q=^Q`MAF4<1!!
 local-user labnario service-type telnet
 local-user labnario level 0
#

header { login | shell }

login – header text is displayed after you are trying to log into a device

shell – header text is displayed after you are successfully logged into a device

Example of configuring header login by using plain text:

[labnario]header login information %
The banner text supports 220 characters max, including the start and
the end character.If you want to enter more than this, use banner file
instead.Input banner text, and quit with the character '%':
welcome to labnario network lab!!!%

Remember that the initial and end characters must be the same. In this case % has been used. The interaction starts after you put % and then enter and automatically closes when you write your header text and put % again.