CCNA,CCNP,CCIE Blogs

What are the Port Roles in RSTP? 1. Root port - It is the port on the switch that has the best root path cost to the root bridge. This is identical to 802.1D. 2. Designated port - The switch port on a network segment that has the best root path cost to the root. 3. Alternate port - A port that has an alternative path to the root, different from the path the root port takes. This path is less desirable than that of the root port. 4. Backup port - A port that provides a redundant (but less desirable) connection to a segment where another switch port already connects. If that common segment is lost, the switch might or might not have a path back to the root. What are different port states in RSTP? 1. Discarding - Incoming frames simply are dropped; no MAC addresses are learned.This state combines the 802.1D Disabled, Blocking, and Listening states. 2. Learning - Incoming frames are dropped, but MAC addresses are learned. 3. Forwarding - Incoming frames are forwa...

What is STP & Redundant Links? Spanning Tree Protocol (STP) is a protocol which prevents layer 2 loops. STP enables switches to become aware of each other so that they can negotiate a Loop-Free path through network. In practical Scenario, Redundant links are created to avoid complete network failure in an event of failure of one link. How STP works? STP chooses a Reference point (Root Bridge) in the network and calculates all the redundant paths to that reference point. Than it picks one path by which to forward frames and blocks other redundant paths. What are the different port states? 1. Disabled - A port in the disabled state does not participate in the STP. 2. Blocking - A blocked port does not forward frames. It only listens to BPDUs. The purpose of the blocking state is to prevent the use of looped paths. 3. Listening - A port in listening state prepares to forward data frames without populating the MAC address table. The port also sends and listens t...

Explain Border Gateway Protocol (BGP) ? Border Gateway Protocol advertises, learns and chooses the best paths inside the global Internet. When two ISPs connect, they typically use BGP to exchange routing information. Enterprises also sometimes uses BGP to exchange routing information with ISPs, allowing the Enterprise routers to learn Internet routes. when we have multiple Internet connections and we want to influence some packets to take one path and some packets to take another we use BGP. Can Routers on different subnet become BGP neighbors? BGP does not require neighbors to be attached to the same subnet. Instead, BGP routers use a TCP connection between the routers to pass BGP messages allowing neighboring routers to be on the same or different subnet. What TCP port number BGP use for connection? BGP uses TCP port 179 for the connection. Difference between eBGP and iBGP neighbor? In iBGP, neighborship is formed between routers within the same AS (autonom...

What is OSPF Routing Protocol? Open shortest path first is an Open Standard Link State routing protocol which works by using Dijkastra algorithm to initially construct the shortest paths and follows that by populating the routing table with resulting best paths. What are the steps required to change Neighborship into adjacency? 1.Two-way communication (using Hello Protocol). 2.Database Synchronization which means exchange of Database Description (DD) packets, Link State Request (LSR) packets, Link State Update (LSU) packets. After Database synchronization is complete, the two routers are considered adjacent. Explain LSA (Link-State Advertisement), LSU (Link State Update) and LSR (Link State Request)? The LSAs (Link-State Advertisements) are used by OSPF routers to exchange routing and topology information. When two neighbors decide to exchange routes, they send each other a list of all LSAs in their respective topology database. Each router then checks its topolog...