Authentication, Authorization, Accounting

AAA is an important feature in networking. AAA stands for Authentication, Authorization and Accounting.

Authentication basically asks users for passwords. It can be done using an internal database of the server/router or it can be done remotely using a RADIUS server (UDP service) or TACACS+ server (TCP service) in order to control users from accessing the network.

To configure AAA service type the "aaa new-model" in the configuration terminal mode. To define RADIUS location type radius-server host "" in the configuration terminal mode. TO define TACACS+ location type "tacacs-server host " in the configuration terminal mode. To apply AAA login type "line vty 0 15" then "login authentication default" also in the configuration terminal mode.

Authorization is used to give permissions to do something on the router or switch configuration. It creates user profiles and determines who can do what. The configuration is "aaa authorization" in the configure terminal mode.

Accounting is used to track users or customers activity. This can be also used to bill customers for their usage of the network.

That is a little bit of the AAA explanation.

Setting passwords on Cisco Routers and Switches

Passwords can be set on Cisco Routers and Switches to make the hardware and the network configuration in it secure. In this blog, I will show you how.

We can add a password for every user that wants to access to the device by entering "enable password " at the configuration terminal of the switch/hardware. In this way, every user will be asked for the password. However, this password is not fully secured since it can be seen on the show running-config command. To make it more secure and encrypted, we can use the "enable secret " command.

The enable secret password has a higher priority than the enable password command, meaning that if both of them are set, the password put in the secret password will be enabled. So, what is usage of the enable password command? Well, this command is used on devices that do not support enable secret password yet.

Cisco routers and switches can be accessed remotely and therefore passwords for this must be configured too. The command is "line vty 0 15" then "password " and then type login to put the command to work. If the password is not set yet, then the remote login will not be available. However, this password is still visible in the show running-config command on the bottom. Basically, a user that wants to login needs to enter the vty password first to get access to the router. After that, it needs to enter the password again to be able to go to the configuration mode of the router/switch (if this has been set before).

Privelege levels on each of the virtual lines can also be set entering the line desired in the configuration terminal mode e.g. "line vty 0 15" and then "privilege level <0-15>". 0 means that the user will be very limited to do operations on the router while 15 means that the user will have full access to configure the router/switch. Combining this with the password commands we can set different privileges based on the password that the user knows. e.g. for line vty 1 we set password line1 and the privilege level of 0, while line vty 2 we set the password line2 and the privelege level 15.

There is also the possibility for accessing the network using a username and password. To do that, we need to set up a database of users and password in the configure terminal mode. Insert then the following structure: "username privilege password ". We can do that for as many users as we want. Now, apply this feature to all of the lines of the router by entering the "line vty 0 15" command in the configure terminal mode. Then type the "login local" command to enable the router to check only for usernames and passwords stored in the local database. After this, the command will be put in play.

Securing your network

Network security is important to keep a safe and secure network. Here are a few tips on securing your network:

- Pay attention to physical security. Put the hardware on locked rooms where only authorized persons can access it. Install the hardwares also in a environment secure place, away from leaking windows, heat generating devices, or possible drowned by flood.

- Set Passwords on the hardware whenever possible. Passwords as they suppose to be, should protect your network and therefore a proper password should be set. Do not set password keys such as "password" or "cisco" because that is too easy to guess.

- Set different privelege levels to different users. In this way, only those who are supposed to only see the network cannot modify the network.

- Give remote access to only those who are authorized to do it. If necessary, set it so that only the specific user with the specific computer (MAC address authorization) can access the network.

- Upgrade the software is necessary. Upgrades comes usually with bug fixes and patches along with additional features.

Comparatives & Superlatives

Comparatives are adjectives used to compare one object to another object. Superlative also compares the object with another object or a group of objects, but shows the highest or the greatest form of adjective compared to the others. People tend to know what it is; the adding of -er or more to the form of adjective for comparative, and the adding of -est or most to the form of adjective for superlative. However, it is often difficult when to use the -er/-est at the ending or use more/most + adjective.

Here is the trick:

1. For 1 syllable use the -er (or just -r or the last consonant + -er). However, pay atttention to the irregulars.

Examples:

- bigger
- good --> better (irregular)
- larger
- hotter
- colder
- warmer

2. For 3 syllable words use more + initial adjective

- reasonable --> more reasonable
- expensive --> more expensive

3. 2 syllable words must be paid attention to: Generally we use more + adjective, except adjectives ending with -er, -y, -ow we must use the -er form.

Example:

shallow --> shallower
lively --> livelier
clever --> cleverer
handsome --> more handsome

Plural forms

Plural form is used for objects more than one. To make a singular object plural:

1. Add -s in general

- computer --> computers
- handphone --> handphones
- pen --> pens
- pencil --> pencils
- apple --> apples

2. Add -es for words ending in ch, sh, x or s

- box --> boxes
- match --> matches
- loss --> losses

3. With words ending in a -y with a consonant before, change the -y to -ies

- baby --> babies
- body --> bodies
- boy --> boys (remember o before the y is not a consonant)

4. There are some irregular form of plural, and some which is always singular such as:

- fish --> plural = fish
- man --> plural = men
- woman --> plural = women
- person --> plural = people
- bread --> also bread (because bread is uncountable)
- water --> also water (uncountable)
- wine --> also wine (uncountable)

Adverbs and Adjectives

The use of adjectives and adverbs is used to add more explanation to the words that come before or after it.

Adverbs are generally used to describe a verb. It is also used to let the user know about the intense of the verb. Usually adverbs ends with -ly. Two other important adverbs are also well and badly (as opposed to good/bad which is an adjective)

Examples:

- The number of people increased erratically --> Describes the verb rise that is unstable
- The boy speaks English fluently --> Describes the intensity of speaking
- The victim reported the event directly to the police --> Describes the time event of doing the report

Adjectives are used to describe nouns or pronouns, and comes usually before the noun itself.

Examples:

- There is a cubical wooden toy --> Describes about the toy (noun) that has a cubical shape and made from wood.
- There is an erratic increase in the number of people --> Erratic here describes the increase (noun) not the verb "is".
- I bought an orange colored orange --> An orange (fruit) that has an orange color.

Adverbs can also be used to describe adjectives (which in turn describes the noun).

Examples:

- You are extremely annoying --> Extremely is an adverb, that describes the adjective word "annoying". Annoying describes the person "you". It can be made clearer by adding words up to complete the sentence such as: You are an extremely annoying person.
- He is really gentle --> Same as above really is an adverb, describing the word gentle (adjective), which in turn describes about the person's character (noun).

Short but powerful basic explanation. Hope that this explanation can make you understand the difference between adverbs and adjectives.

Common mistakes using past tense I

Everybody knows the past tense, and the structure of simple past tense (verb + past participle). However, two of the mistakes people use are quoting and common facts.

1. Quoting.

When we quote from someone, we must use the correct sentence at that moment, which is usually the present tense. We must use the exact words the person says at that moment. For example: "Today was my birthday," she said yesterday. That is not a correct form of grammar since she said it in the present form on yesterday. Therefore it should be "Today is my birthday," she said yesterday.

2. Common facts.

Common facts are something that doesn't change and is generally believed as true, therefore must always be used in the present form. The earth is round, 4+4=8, a dog is an animal. However, facts that can change should take the appropriate time form.

For example:
- She asked last week why cheese is a dairy product.
- The man didn't believe that the earth is round, when I told him yesterday.

However, opinions should take the the correct time, since they can change. e.g I found a computer yesterday that was only $50. It is a fact that the computer costs $50, however, it can change its price in the future and therefore not a common fact.

So, a final example comprehending the correct sentences regarding the matter above :

- Everybody asked yesterday why 5+5 is 10. I could not answer the question, and asked back why the earth is round. "Those are just common facts," I replied.
- I bought strawberry jam which is made from strawberries because it was on sale for $1.