What is virtualization


What is virtualization?
Nontechnical definition-Virtualization word comes from virtual means not real.Anything which appears real but not actually can be termed as virtual.The process of getting that real thing into virtual is called virtualization.

Technical definition-Emulation of the underlying raw hardware.

In Information Technology industry virtualization was there for quite long time.In older days when people were using 512MB HDD and 1GB HDD's (yes those were the days when 1GB was huge).The HDD manufacturers came with 8GB Hdd.The BIOS limitation was 2GB that means you could not attach the HDD more than 2 GB to the computer as it would not get detected by the machine.How manufacturers overcame this problem is by fooling the BIOS that it is using 2GB HDD.The process was called LBA(Logical Block Addressing).This was also a virtualization.
Then the products were started coming in the market like Vmware Workstation.

What is Vmware workstation?
You can load this piece of software on the Operating System like Windows XP.Then you can create as many as machines through this software.The Virtual machine inside the software will have its own memory.You can load any Operating System on it.It will use the processing power and memory from its master machine but will act independently.It will have its own IP address.You can run applications on it and if it crashes then just restart itfrom inside the software.Your master machine will not get affetced.

Benefits of Virtualization
To an individual
-He can create separate virtual machines for different purposes
-Like the main master will have Windows XP and inside he can keep Redhat Linux so he can use applications which were not available in Windows XP.
-If the machine crashes he can rebuilt the new one within minutes

To an Organization
-Organization can keep server operating system on these virtual machines.
-If the server crashes they can put the data immedialtely on the second available server to improve an SLA(Service Level Agreement)
-The new products from Vmware (Vsphere) can transfer the online server on the fly from one virtual machine to another removing the need to shutdown the server (that means there can be 100% uptime)
-They can keep there data in a virtualized way(storage virtualization)
-They can use different datacenters for disaster management and use virtualization for the same.


What are different virtualization products?
There are lots of free and commercial products available for virtualization

Free products
Vmware Workstation
Vmware Server
VMware ESXi
Xen
Microsoft Virtual PC
Microsoft Virtual Server
Qemu
Microsoft HyperV
GNS
FreeNAS

Commercial Products
Vmware Vsphere
Vmware ESX
KVM
Openfiler
Hp Lefthand


The total list and there comparison is at
http://en.wikipedia.org/wiki/Comparison ... l_machines

How it is affetcting the IT industry?
-This saves the cost of buying the special hardware for each resource
-You can save cost for sharing the users desktop on the server which is in the datacenter.This technology from Vmware is called VDI (Virtualized Destop Infrastructure).
-You can host multiple servers on one single machine and use its resources to the full limit.e.g you can have 10 servers installed on one ESX server thus saving the rack space, electricity consumtion.
-Enterprises can meet the SLA (Service Level Agreements) made to their clients by using virtualization products.

What products you can virtualize
-You can virtualize your Servers, computers,network devices,storage devices.
Server-Vmware ESX,Xen,Microsoft Virtual Server,Microsoft HyperV,Xen
Desktops-Vmware Workstation,Microsoft Virtual PC,Xen
Network devices-Qemu,GNS,KVM
Storage Devices-Openfiler,HP lefthand,FreeNAS


Future of Virtualization
Virtualization holds tremendous growth opportunity as more and more products in our daily life are getting virtualized and we will not ever know that we are using
virtualization in the backend.

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EIGRP Notes Part 4


Load Balancing
EIGRP automatically load balances across equal-cost links.

Unequal-cost load balancing is enabled by specifying a variance. Feasible successors with a feasible distance less than (best path FD * variance) will be proportionally utilized.
Router(config-router)# variance <multiplier>
Variance can be between 1 and 128; default is 1 (equal-cost only).

EIGRP Tuning
EIGRP timers do not have to match for two routers to form an adjacency.
Default hello timer:
High-bandwidth links (>= T1): 5 seconds
Low-bandwidth links (< T1): 60 seconds

Hello timers are modified per interface:
Router(config-if)# ip hello-interval eigrp <ASN> <seconds>

Default hold timer = 3 *
Reconfiguring the hold timer is done in seconds, not as a multiplier:
Router(config-if)# ip hold-time eigrp <ASN> <seconds>

Authentication
Authentication types:
Plain-text password (insecure)
MD5 hash
Configuring MD5 authentication on an interface:
Router(config-if)#ip authentication mode eigrp <ASN> md5
Router (config-if)# ip authentication key-chain eigrp <ASN> <chain name>
Router(config)# key chian <chain name>
Router(config-keychain)# key 1
Router(config-keychain-key)# key-string <password>

Bandwidth Manipulation
Bandwidth of an interface can be administratively configured:
Router(config-if)# bandwidth <kilobits>

The bandwidth setting will not affect the actual interface speed, only the value used in metric calculation.This is useful for serial interfaces which connect to a DSU operating at a slower speed.EIGRP assumes all virtual circuits on an interface receive an equal share of the total bandwidth.By default, EIGRP will use no more than 50% of an interface's bandwidth. This can be adjusted as such:
Router(config-if)# ip bandwidth-percent eigrp <ASN> <percentage>

Verifying EIGRP Operation
Monitoring
show ip eigrp neighbors
show ip eigrp topology
show ip eigrp traffic
show ip eigrp interfaces
show ip route eigrp

Debugging
debug eigrp packet
debug ip eigrp neighbors
debug ip eigrp
debug ip eigrp summary

EIGRP Notes Part 1
EIGRP Notes Part 2
EIGRP Notes Part 3


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EIGRP Notes Part 3


Enabling EIGRP:
Router(confi)# router eigrp <ASN>

Adding a network to EIGRP:
Router(config-network)# network <network> [wildcard mask]
All interfaces belonging to the specified network will become EIGRP capable and advertised via EIGRP.EIGRP will summarize to classful boundaries by default.

An interface can be set to ''passive'' to prevent advertisement:
Router(config-router)# passive-interface <interface>
If an interface is included in the network configuration but set to passive, it will still be included in EIGRP advertisements. If an interface is not included in an EIGRP network, it will not be advertised in EIGRP.

Summarization in EIGRP
Summarization is key to preventing looping route queries (which leads to SIA condition).

Disable automatic summarization to classful addresses:
Router(config-router)# no auto-summary

Configure manual summarization on an interface:
Router(config-if)# ip summary-address eigrp <ASN> <network> <subnet mask>

Stub Routers in EIGRP
Stub routers participate minimally in EIGRP, which reduces utilization of memory and CPU on the
router.
Often used in lieu of static routes in a hub-spoke topology to provide a standard configuration for all spoke routers.
Router(config-router)# eigrp stub [options]

receive-only - Prevents the router from advertising any routes
connected - Permits advertisement of connected networks (default)
static - Permits redistribution of static routes
summary - Advertises summary routes (default)

EIGRP Notes Part 1
EIGRP Notes Part 2
EIGRP Notes Part 4

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