System Management

I’ve had only one case when I used this command and … full success.

Sometimes it can happen that the file system doesn’t work properly. When you run dir command, you can find the space, which usage status is unknown. The system prompts you that the file system should be restored. Then you can run fixdisk command to release the unknown space.

Notice that:

• It is not recommended to use it when the file system works correctly.
• It doesn’t help when physical medium is damaged.
• Do not use it when CPU usage is high.

Lost chains in flash detected, please use fixdisk to recover them!
<labnario>fixdisk flash:
Fixdisk flash: will take long time if needed
%Fixdisk flash: completed.

I have busy time now and a frequency of updating my blog is not such as I would expect. Sorry for that. I hope it should be better soon.

But today I would like to ask you a simple riddle.

Let’s assume that we have S9300 switch and a fragment of its configuration:

#
observe-port 1 interface Ethernet0/0/1
#
acl number 3000
rule 5 deny ip source 89.168.24.0 0.0.0.255
rule 10 deny ip source 91.10.10.0 0.0.0.255
rule 15 permit ip
#
traffic classifier riddle operator and
if-match acl 3000
#
traffic behavior riddle
mirroring to observe-port 1
statistic enable
#
traffic policy riddle
classifier riddle behavior riddle
#
interface Ethernet0/0/10
traffic-policy riddle inbound

The Link Layer Discovery Protocol (LLDP) is an layer 2 discovery protocol defined in the IEEE 802.1ab. How does it work? The LLDP protocol collects information about local interfaces, sends this information to neighbours, and receives information from the neighbours as well. In short, when the LLDP protocol runs on devices, the NMS can obtain the Layer 2 information about all the devices it connects and the detailed network topology. It does it by searching the layer 2 information in Management Information Base (MIB). NMS uses LLDP management address to identify the device. Trap message is triggered in case when local management address is changed, LLDP is enabled or disabled globally and there are changes on neighbouring devices.

Lets try to configure LLDP based on the following topology:

First of all configure SNMP trap for LLDP:

[Switch]snmp-agent trap enable feature-name lldptrap

[Quidway]dis snmp-agent tr feature-name lldptrap all
------------------------------------------------------------------------------
Feature name: LLDPTRAP                      
Trap number : 4         
------------------------------------------------------------------------------
Trap name                       Default switch status   Current switch status 
lldpRemTablesChange             on                      on                  
hwLldpEnabled                   on                      on                  
hwLldpDisabled                  on                      on                  
hwLldpLocManIPAddrChange        on                      on

Simple Network Management Protocol (SNMP) is widely used for IP networks’ devices management and monitoring. Not only routers and switches can be managed using SNMP. It can be used with servers, modems, printers, etc. It is application layer protocol and is defined as IETF standard.

How SNMP works?

It operates based on the following components:

• Network Management Station (NMS), sends SNMP requests to query managed devices and receives alarms send by these devices. NMS uses the MIB to identify and manage device objects.
• Agent – process running on the managed device which is responsible for sending alarms to the NMS and processing requests received from NMS.
• Managed device – a networking device on which the Agent process is running.

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.