Passive Interface

Overview: A passive interface prevents sending OSPF messages out interfaces that are not connected to another OSPF router.   Study Notes: Passive interfaces help to more efficiently use bandwidth Passive interfaces help to more efficiently use router resources Passive interfaces lessen the security risk Passive interfaces can be set per interface that is enabled for […]

CCNA 3.1.c: Frame Rewrite

Overview: Frame rewrite is a crucial step in routing a packet through a router.  Frame rewrite is determining how to construct the Layer 2 frame header to allow the packet to be properly encapsulated toward its next hop and forward the packet out the correct interface.   Study Notes: Here is the process: Packet arrives […]

CCNA 3.1.b: Forwarding decision based on route lookup

Overview: Routers have many different routes in their tables, but need to have a fast way (forwarding decision) to find the best path to a destination network.   Study Notes: A prefix is a network address and a route mask Typically, the forwarding decision in a router is based on three processes – Routing protocols, […]

CCNA 3.1.a: Packet handling along the path through a network (FREE LAB!)

Overview: Understand how a packet is handled by different devices along a path in a network.  In this scenario, the sender is PC1 and the receiver is PC2. Study Notes: PC1 creates a packet with the destination IP address of PC2 PC1 determines that PC2’s IP address is on a different network PC1 looks up […]

CCNA 3.1: Describe the routing concepts

Overview: Routing concepts describe the way a packet transits a network from source host to destination host.  Layer 2 and Layer 3 protocols are required to receive the packet, deencapsulate it, determine the destination, determine the exit interface, encapsulate it and transmit it. The following are the routing concepts covered in the CCNA: Study Notes: […]