Tag Archives: Huawei CLI

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:

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
#

If you want to look into packets sent or received by a router, and there is no possible to display them by command, the simplest and fastest way is to use mirroring. Unfortunately, in case of AR routers, you have to go on-site to connect packets’ analyser (for example Wireshark). Comparing to NE routers, AR routers do not support remote mirroring.

There are two types of mirroring on AR routers:

• port mirroring

Port mirroring is to copy all packets from mirroring port to another port, which is called monitor port. Monitor port is that where a monitoring device is connected to. AR routers support local port mirroring for inbound and outbound direction.

• traffic mirroring

Traffic mirroring is to copy specified packets, by QoS policy, to a specific destination and send them to an interface for analysis. Traffic mirroring is supported on AR29 and AR49 routers.

What is NQA?

It is a feature that functions above link layer to measure performance of protocols running at the network layer, transport layer and application layer. It is useful to monitor network and locate faults occurring in the network. NQA can accurately test the network and collect statistics as well. You can configure and display NQA statistics through CLI but, as NQA is fully supported by Huawei NMS, you can also do this in GUI.

Most of Huawei devices support NQA but configuration can vary a little bit between NE routers, AR routers and switches. Of course we can perform more advanced test on carrier class devices. In this post we will focus on CLI and use CX600 router as an example.

NQA tests supported by CX600:

• • ICMP test
  • DHCP test
  • FTP test
  • HTTP test
  • DNS test
  • Traceroute test
  • SNMP test
  • TCP test
  • UDP test
  • ICMP Jitter test
  • UDP Jitter test
  • LSP Ping test
  • LSP Traceroute test
  • LSP Jitter test