Understand VLAN like never before!!

I consider vlan to be a dome like structure in a real world. What will happen if 10 people i.e. human beings are left in a closed dome like structure a.k.a vlan. Yeah, probably they all will survive with food and O2 and they can also talk to each other & share their GF-BF stories.

But the question is why they are able to talk to each other; probably they are all humans and so they understand each other Or probably they are all English speaking dudes. Good. Lets call all these English speaking dudes originated from same family. Can we call them 1 family, OR 1 LAN members common to them all is ENGLISH.

So morally all English speaking dudes can talk to each other in a dome closed structure. Now, assume we add two more people in that dome that adds up to total strength being 12 now. Unfortunately, those two speak only either Hindi or Chinese. Will the 10 English dude be able to talk to and understand those 2 Hindi/Chinese or vice-versa?? Naaaaah!!! Not until some a 1000 years evolution or a new paradigm change on the way they express themselves.

This is like a situation where 10 people in a LAN who all understand English can't talk to 2 people who only understand either Hindi or Chinese. Can we say those 2 are not in a family or VLAN despite being in that dome. Now if you replace those 10 people with a network address in 10.10.10.0 255.255.255.0 and assign them IP from 10.10.10.1 -10 they all will talk to each other beautifully. Eventually the Chinese/Hindi guys will be member of a different family say 10.10.20.0 255.255.255.0 and are deprived of any communication between the two families.

Now , suppose there is one more dome number 2 parallel to above dome number 1. Here we have 2 domes in total but since both are unique independent closed structure, people from dome 1 and 2 can't talk to each other. Assuming there are 10 English speaking people & 2 Chinese/Hindi Speaking  in dome 2 as well, it means it is exact replica of dome 1.
Now the 10 english speaking from dome 1 can't talk to 10 english speaking people in dome 2 & similary from the 2 chinese/Hindi speaking chaps.

What if I create a HOLE in Dome 1 & Dome 2 connecting it through a rubber tube of a Tyre. But the privilege is that the HOLE was created by English people on both the sides so they own the rubber tube/tunnel to communicate with the other side.

The two Chinese/Hindi in both the domes 1/2 won't be able to pass their words to each other since they don't have any hold on the tunnel nor do they have money to dig on their own.

Supposedly, one night the 2+2 Chinese/Hindi speaker on both side got some money miraculously and dug a HOLE which they own. Now 2 Chinese/Hindi Speaking can talk to each other through their independent HOLES( in their respective domes) which they own.

These two independent HOLES( connected via tube)  created by both the Englishmen and the CHINESE/HINDI speaker can be called two ports belonging to two vlans or to two different family.

One day one storm hits both the domes and ENGLISHMEN lose their rubber tube tunnel, therefore, the communication between dome 1 and dome 2 English guys snapped. They were drawing a plan to create more domes but lost contact after the storm passe but the 2 CHINESE/HINDI speaker's tunnel is intact and OK.

For the time being ENGLISHMEN used their policy and offered pizzas to the 2 CHINESE/HINDI speaker's in lieu to use their tunnel for their communication. Since 2 CHINESE/HINDI speaker's got something new for their taste-buds they agreed to share the rubber tube tunnel with the 10 ENGLISHMEN on both the sides.

This way both sides could talk to each other happily without any further disruptions. This common use of tube can be called a trunk which carries information for both the ENGLISHMEN& CHINESE/HINDI family or vlans.

I hope you enjoyed the story and had fun imagining it.

Good Luck!


-Anupam

IP accounting - Cisco Press

Read IP accounting, though not used much these days, but a nice feature on security and inspection level.

Uses:

1. IP accounting L3, which is configured only on outbound and doesn't take into account the traffic terminating or originating on the router itself. Maintains Acitve and Checkpoint database to store the history and active traffic logs,

2. IP Accounting ACL checks the traffic which doesn't match any specific acl. A range of IP address can be provided. Can be put on both ingress and egress ports. Keep incrementing the hits for a subset of address. Collected data is accessible via CLI and SNMP; however, the initial configuration is required via CLI. To retrieve the collection results via SNMP, you need to enable SNMP on the router first. When configuring SNMP, distinguish between read-only access and read-write access.

3. IP accounting MAC for LAN etc. Best for usage billing per IP id per customer. Has only active logs visual feature

4. IP Accounting Precedence: provides IP precedence-related traffic accounting information. The collection per interface consists of the total number of packets and bytes for each of the eight IP Precedence values, separately per direction (send and receive).Sub-interfaces can be helpful for per user.

Link to IP accounting by Cisco Press

Good Luck!