All about wireless networking and NMS/EMS

To check the packages installed on linux machine: #rpm –qa # rpm -qa | wc -l (to check the count of packages installed) #rpm -ql <rpm_name> (to check the details of installed rpm) Command to check RPM signature of package: #rpm --checksig <packagename> Command to install RPM package in linux: #rpm -ivh <packagename> -i : install a package -v : verbose for a nicer display -h: print hash marks as the package archive is unpacked. Command to check dependencies of RPM Package before Installing: #rpm -qpR <packagename> -q : Query a package-p : List capabilities this package provides. -R: List capabilities on which this package depends.   Command to Install a RPM Package Without Dependencies: #rpm -ivh --nodeps  <packagename> Command to upgrade rmp package: #rpm -Uvh <Packagename> Command to un-install an RPM package: #rpm -evv <Packagename> Command to Remove an RPM Package Without Dependencies: #rpm -ev --no

To check the packages installed on linux machine: #rpm -qa# rpm -qa | wc -l (to check the count of packages installed) #rpm -ql <rpm_name> (to check the details of installed rpm) Command to check RPM signature of package: #rpm --checksig <packagename> Command to install RPM package in linux: #rpm -ivh <packagename> -i : install a package -v : verbose for a nicer display -h: print hash marks as the package archive is unpacked. Command to check dependencies of RPM Package before Installing: #rpm -qpR <packagename> -q : Query a package-p : List capabilities this package provides.-R: List capabilities on which this package depends.   Command to Install a RPM Package Without Dependencies: #rpm -ivh --nodeps  <packagename> Command to upgrade rmp package: #rpm -Uvh <Packagename> Command to un-install an RPM package: #rpm -evv <Packagename> Command to Remove an RPM Package Without Dependencies: #rpm -ev --nodeps <

To check linux version [root@sys-218-25 ~]# uname -r 3.10.0-229.el7.x86_64 [root@sys-218-25 ~]# cat /etc/redhat-release Red Hat Enterprise Linux Server release 7.1 (Maipo)

Security Levels: SNMP offers 3 different security levels: noAuthNoPriv AuthNoPriv AuthPriv Auth stands for  Authentication  and Priv for  Privacy  (encryption). noAuthNoPriv =  no authentication and no encryption . AuthNoPriv =  authentication but no encryption . AuthPriv =  authentication AND encryption. #snmp-server view iso iso included Explanation: snmp-server view (enter view name) (mib name) include/exclude #snmp-server engineID remote 9.1.48.127 1234567890 Explanation: This step is not mandatory to configure #snmp-server group prime v3 priv read iso write iso Explanation: snmp-server group (group_name) v3 priv read (enter view name) write (enter view name). Here Priv means configuring AuthPriv #snmp-server user tester prime v3 auth md5 public123 priv des public123

Inter - Vlan Routing  is the capability to  route  traffic between  vlans . This functionality could be on the Switch itself (for Layer 3 Switches).  By default, only hosts that are members of the same VLAN can communicate. Inter-VLAN Routing Architectures Within a LAN topology, inter-VLAN routing is used to route packets between different VLANs. Three common inter-VLAN routing architectures are used in modern LAN networks today: Router-on-a-stick. Router-on-a-stick using trunks. Layer 3 switching. This section examines each of these in detail, outlining any restrictions or issues associated with each. Router-on-a-Stick The  router-on–a-stick  architecture is the most basic method of inter-VLAN routing. In this architecture, a router is simply connected to each VLAN and forwards inter-VLAN traffic between the appropriate VLANs.  Figure 1  shows this architecture. Figure1  Router-on–a-Stick As you can see in  Figure1 , the router has a physical Ethernet interface

Access Port: An access port can have only one VLAN configured on the interface; it can carry traffic for only one VLAN. Frames coming in to the interface will be tagged and Frames going out to the interface will be untagged. Trunk port: A trunk port can have two or more VLANs configured on the interface; it can carry traffic for several VLANs simultaneously. Allow all the tagged packets or tagged packets of configured vlan on the particular port. Switch port configured as a  trunk port  send and receive  IEEE 801.q VLAN tagged  Ethernet frames . If a nontrunking port receives an 802.1Q frame, the source and destination MAC addresses are read, the tag field is ignored, and the frame is switched normally at Layer 2. Native VLAN: If a switch receives  untagged Ethernet frames  on its Trunk port, they are forwarded to the  VLAN  that is configured on the Switch as native VLAN. Both sides of the  trunk link  must be configured to be in same native VLAN. An 802.1Q tr

What is QinQ In this section, we will see about Switching concept QinQ. In service provider networks, This is very important. Service provider use this Switching function to pass customer data from one end to other end with two vlan id’s in own switching network.  Explanation: The QinQ technology is called VLAN dot1q tunnel, 802.1Q tunnel, VLAN Stacking technology. The standard comes from IEEE 802.1ad and it is the expansion of the 802.1Q protocol. QinQ adds one layer of 802.1Q tag (VLAN tag) based on the original 802.1Q packet head. With the double layers of tags, the VLAN quantity is increased to 802.1Q. QinQ encapsulates the private network VLAN tag of the user in the public(service provider) network VLAN Tag to make the packet with double layers of VLAN Tags cross the backbone network (public network) of the operator. In the public network, the packet is passed according to the out layer of VLAN tag (that is the public network VLAN Tag) and the private network

Inbound, ingress = traffic coming to the device or interface. Outbound, egress = traffic leaving the device or interface.

The  address resolution protocol  ( arp ) is a  protocol  used by the Internet  Protocol  (IP), to map IP network addresses  to the hardware  addresses  used by a data link  protocol . The  protocol  operates below the network layer as a part of the interface between the OSI network and OSI link layer. ARP Cache:            Since sending an ARP request/reply for each IP datagram is inefficient, hosts maintain a cache (ARP Cache) of current entries. The entries expire after 20 minutes. ARP Packet format

SNMPv1 :  Five operations/PDU: GET-RESPONSE, GET-NEXT, GET-request, SET, TRAP. Security: Community based. (No authentication no privacy) SNMP Community strings are not encrypted(clear-text) in v1 & v2c. Community string will be easily identified by packet sniffer. SNMPv2c :  Two new operations/PDU – GET-BULK(efficient retrieval of multiple OIDs), informs (trap + ACK mech.), plus 64-bit object support. Security: Community based. (No authentication no privacy) SNMP Community strings are not encrypted(clear-text) in v1 & v2c. Community string will be easily identified by packet sniffer.   SNMP v3: PDUs: Includes all the v1&v2c  pdu's. Security: New architecture including security functionality; authentication (SHA, MD5), privacy (encryption - DES, 3DES, AES). Uses Authentication(MD5 or SHA). Encryption using CBC-DES(Adds DES 56-Bit Encryption in Addition to Authentication Based on DES-56).

Management Information Base (MIB): •         A MIB is a collection of “managed objects” which contain information. •        A MIB defines the variables that reside in a managed node,Defined according to SMI (Structure of Management information) rules,Each managed object is described using an object identifier defined in the SMI. •        MIB I: 114 standard objects, Objects included are considered essential for either fault or configuration management. •        MIB II: 185 objects defined •        Other standard MIB Some Common MIB’s interface MIB(RFC 1907), interface MIB(RFC2233), IP MIB(RFC4293), TCP MIB(4022). MIBs – Object Identifiers:               Each managed object within a MIB has a unique object identifier.  SNMP uses these object identifiers to identify the MIB variables to retrieve or modify.  Objects that are in the public domain are described in MIBs introduced in Request for Comments (RFCs).

In network management,  Trap   is a message sent by agent to manager. Two broad categories of traps are generic and  specific , cold start and warm start being the  generic  traps. Here is the difference between two: Cold Start:  This trap indicates that sending device is re-initializing itself such that the agent’s configuration may be altered. Generic trap 0 - coldstart Issued whenever the SNMP agent is re-initializing. Configuration data has changed. Warm Start : This trap indicates that sending device is re-initializing itself such that the agent’s configuration is not altered. Generic trap 1 - warmstart Issued whenever the SNMP agent is re-initializing. Configuration data might change. Note that cold start & warm start traps have nothing to do with self reboot or hard reboot of network element. Only difference between the two is the change in agent’s configuration with cold start trap.

A Network Manager’s job is to get data from Network Elements and present it to the administrators or operators. There are two ways of doing this activity:  1) Polling and 2) Trap . Here is a quick difference between the two: Polling  : A traditional way of providing operators with the network elements information. It’s characteristics are as follows: ·        Pull Mechanism – Requests and get information from network elements at periodic intervals. The periodic interval is most often configurable. ·        Provides non-real time information. It may happen that some changes happen in network element but polling happens an hour after that. Thus, operator gets to know about the changes after an hour. ·        Higher bandwidth needed. Traps  : When an alarm situation exists a trap can be generated, or if some changes happen at network element, an attribute value change event can be generated by the agent. It’s characteristic are as follows: ·        Push Mechanism – E

SNMP Manager: Responsible to communicate with SNMP agent implemented network devices. S NMP Manager’s key functions 1)    Queries agents 2)    Gets responses from agents 3)    Sets variables in agents 4)    Acknowledges asynchronous events from agents SNMP agent: A program packaged with NE. Enabling the agent allows it to collect the management informantion database(MIB) from the device locally and makes it available to the SNMP manager. SNMP agent’s key functions 1             1)    Collects management information about its local environment 2             2)    Stores and retrieves management information as defined in the MIB. 3             3)    Signals an event to the manager. 4             4)    Acts as a proxy for some non–SNMP manageable network node.           Ex: SNMP Agent=Net-SNMP

Every network engineer should know how packets are routed in network. Its a very simple question asked in every interview. IP Packet Delivery on a Local Area Network is a fundamental concept, all system and network administrators should have a clear understanding of. How do computers decide to where to send the packets to?  Should they send them directly to the target computers or the gateway, or both?  The answer is simple. Computers use their local ROUTING table to make that determination.  Yes, even computers have a routing table.  Actually, if a network host is using TCP/IP to communicate on the network, it will have a routing table. Command to check the route info on computer is route PRINT Here is an example of a routing table taken from a computer with an IP address of 192.168.0.1. If you read through this routing table, you will notice that if a packet's network destination address is anything other than an a