Dynamic Routing Protocols:
Dynamic routing helps the admin overcome the time-consuming process of configuring and maintaining static routes.
Routing protocols have been used since the early 80s.
Routing algorithms have been in use since 1969.
Some function(s) of Dynamic Routing Protocols:
Dynamically share information between routers.
Automatically update routing table when topology changes.
Determine best path to a destination.
Tags: vtp, vlan, switch, study, router, guides
Introducing the Topology:
The show controllers command reveals whether the cable is DCE or DTE.
#show controllers serial 0/0/0
Interface serial0/0/0
Hardware is powerQUICC MPC860
DCE v.35, no clock
Interfaces:
By default all Serial and Ethernet interfaces are down.
The routing table will be empty.
Debugging:
Allows us to watch changes a router performs in real time.
For example, to observe routes being added and removed.
#debug ip routing
#undebug all (disables all debug commands). or
#no debug all. or
#un a. (short form)
Tags: 802.1q, study, vlan, switch, vtp, wan
Routing & Packet Forwarding
Routing Protocols & Concepts
Router as a Computer:
Computers that specialize in sending packets over the data network.
Responsible for interconnecting networks.
Routers are the network center.
Generally have a min of 2 connections:
WAN connection (Connection to ISP).
LAN connection.
In addition to packet forwarding, routers provide other services as well.
A router connects multiple networks.
This means that it has multiple interfaces that each belong to a different IP network.
Each network that a router connects to typically requires a separate interface.
Routing Table:
Used to determine the best path.
Incoming packets’ dest IP address is looked up in the table.
The table includes an exit interface or next hop.
Once a match is found, the router encapsulates the IP packet into the L2 frame of the exit interface.
Router as a computer:
Router components and their functions:
CPU – Executes OS instructions.
RAM – Contains the running copy of config, routing table, buffers, etc. Contents lost when pwr is off.
ROM – Holds diagnostic software used @ startup and the bootstrap prgm.
NVRAM – Stores startup config.
Flash – Contains the OS, non-volitile.
Interfaces – usually multiple physical interfaces. Examples of interface types:
Ethernet / Fast Ethernet interfaces.
Serial interfaces.
Management interfaces (concole).
Internetwork Operating System:
IOS
A multitasking OS integrated with routing, switching, internetworking, and telecomm functions.
Stored as an image. Many different IOS images available.
IOS interface is CLI
On boot, the startup-config file in NVRAM is copied into RAM and stored as the running-config file.
Changes entered by the admin are stored in the running-config and are immediately implemented by the IOS.
Tags: switch, ip, 802.1q, guides, router, study
Grouping Devices into Networks and Hierarchical Addressing :
The original Internet – a few trusted users, no security issues.
Security needs have changed dramatically.
Dividing networks based on ownership means access can be prohibited, allowed, or monitored.
E.G. college network – admin, research, and student networks.
Security between networks is implemented in a router or firewall at the perimeter of the network.
The Internet = millions of hosts identified by a unique IP.
If each host had to know the address of all hosts it would severely degrade their performance.
Dividing networks so hosts who need to communicate are together reduces overhead (o/h) of hosts needing to know all IPs.
For all other destinations, hosts only need to know the address of a router.
This router is called a gateway. It serves as an exit from that network.
Hierarchical Addressing:
A hierarchical address uniquely identifies each host.
It also has levels that assist forwarding packets across internetworks, enabling division based on those levels.
So, hierarchical addressing supports communications between internetworks.
Postal addresses are examples of hierarchical addresses.
Refering only to the relevant address level (country, state, city, etc.) at each stage makes this process very efficient.
No need at each stage to know the all details (except Last).
IP addresses work in a similar way.
IP addresses have a network portion and a host portion.
Routers forward packets between networks using only the network portion.
Once delivered, the whole address will have been used to deliver the packet.
If necessary, additional layers of addressing can be created (subnet portion).
Tags: switch, interface, guides, vlan, ip, cisco
Bitmindframes cisco study guides
INTERVLAN ROUTING
A VLAN is a broadcast domain and unique ip subnet
Switches operate at layer2 (Data link Layer)
VLANS cannot communicate without L3 (Network Layer)
The L3 communication is called inter-vlan routing
Inter-vlan routing is a process of forwarding network traffic from one vlan to another using a router
The Subnets of your network facilitate the routing process.
Router interfaces can be connected to separate vlans.
Devices on vlans send traffic through the router(L3) to other vlans.
Traditionally vlan routing required multiple interfaces.
Each interface was connected to a separate switch port & configured with a different subnet
The switch port is connected to the router in access mode.
Tags: study, 802.1q, vtp, router, cisco, guides
