All about wireless networking and NMS/EMS

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  ...

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 confi...

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 netw...

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 identifie...