OSPF routing protocol is 100 percent loop-free protocol. It is the most commons Interior gateway protocol used by most of the organizations. Whether the protocol is using IPv4 or IPv6 it works in the same way in both cases because its metric is bandwidth and bandwidth is considered in layer-1 and layer-2 so regardless of which protocol it uses it works in the same way. This is the typical network where right in the middle there is a loop but if we use OSPF as Read more [...]

Routing Protocols

Cisco classifies its routing protocols into two categories, Interior gateway protocols (IGP) and Exterior gateway protocol (EGP). Gateway protocols means that path to the another network , in other words it is a route to another network. The term router and gateway are interchangeable. Interior Gateway Protocol This is the routing protocol in a typical LAN environment. The key points to notice that you hold all the routers and all the routers know all the paths to different networks. RIP is Read more [...]

Trunking and DTP

Dynamic trunking protocol (DTP) automatically connects and configure trunks among switches. We will use DTP here and will discuss pros and cons of this protocol. There are two standards for trunk ISL and 802.1q. ISL is Cisco proprietary and not much used; 802.1q is open standard and used almost everywhere. When you have trunking mode to auto then you will see the following configuration. Notice that the encapsulation is n-802.1q which tells that Read more [...]

Inter-VLAN Routing

We create Virtual Local Area Network (VLAN) to isolate the network, meaning that separating the traffic of different departments in an organization. This also divides the one big broadcast domain into multiple small broadcast domains.In some cases we have to communicate the different VLANs, for instance if we have a printer in sales department and production also wants to use this then we need a communication between these separate VLANs. For this purpose we use inter-VLAN routing, which means routing Read more [...]

Understanding VLANs

By default the Cisco switches do not break the broadcast domain and what VLAN does it breaks the one physical switch into multiple virtual switches to isolate the broadcast domain.Broadcast slows the network traffic due to a lot of broadcast requests. CSMA/CDAny time your computer goes to talk only one person can talk on electrical wire at any given time. If two people talk at same time and electrical pulses hit each other and you get collision.So before you talk you have to sense the wire whether Read more [...]

DHCP relay agent

When a device is configured as a DHCP client, it will send a a broadcast packet to discover DHCP servers on the network. Broadcast packets are not forwarded by routers by default, so if a DHCP server is in a different network than the DHCP client, it will not receive the request. Consider the following scenario:The workstation on the left is configured as a DHCP client. R2 on the right is configured as a DHCP server. The workstation sends a DHCP discover packet, but it receives no request, since Read more [...]