What’s so Merry about Christmas?

Society has turned up to be as fictitious as i was observing many of my friends sent me Christmas greetings through many means.. cells, messenger, facebook etc.. many knows that i’m not a follower of christianity itself but idk.. many of non-followers alike has chosen to becomes a herald of the celebrations itself as to achieve the goal of peace and tolerance towards one another..  well., i  replied their greetings as a show of respect but i don’t usually invoke it in the first place..

I praise Christmas holidays don’t get me wrong.. i cherish on the overall positive impacts on our economy… thrive spending, parties, celebrations, well.. it gave colors to life and made it more meaningful i guess.. as Y2010’s ending soon, it’s time for me to examine my budget for next year as well.. and reflect back, examines on the spendings i’ve gone through for the past years… AFAIK i’ve overspent 2k compared to last year.. T_T

I’m looking at the stars, they’re so far away, and their lights takes so long to reach us… all we ever see of stars are their old photographs..

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Router on a Stick (ROAS)

ROAS is the terminology for enable routing between two VLANs on a simple Layer 2 switch using a Cisco router with just one interface.. A cisco layer 2 switch (sw1) carries two VLANs (10 and 20) with 3hosts connected (the PC3 is not). PC1 belongs to network subnet 2.1, PC2 belongs to network subnet 3.1. by default if the switch is just a normal layer 2 switch, the hosts can’t communicate betwen them because they belong to different VLANs and there’s no routing. thus if i want to provide network connectivity between the 2 LANs, i need to have a layer 3 engine somewhere in the network.. so i use a router to provide layer 3 connectivity

Switch config
# conf t
(config)# int fa0/0
(config-if)# switchport trunk encapsulation dot1q
(config-if)# switchport mode trunk
(config-if)# exit

(config)# int fa0/1
(config-if)# switchport mode access
(config-if)# switchport access vlan 10
(config-if)# exit

(config)# int fa0/2
(config-if)# switchport mode access
(config-if)# switchport access vlan 20
(config-if)# exit

Router config
# conf t
(config)# int fa0/0.10
(config-if)# encapsulation dot1q 10
(config-if)# ip address 192.168.2.254 255.255.255.0
(config-if)# exit.

(config)# int fa0/0.20
(config-if)# encapsulation dot1q 20
(config-if)# ip address 192.168.3.254 255.255.255.0
(config-if)# exit

PC config (PC1)

# conf t

(config)# int fa0/0

(config-if)# ip address 192.168.2.1 255.255.255.0

(config-if)# no shut

(config-if)# exit

(config)# ip route 0.0.0.0 0.0.0.0 192.168.2.254

PC config (PC2)
# conf t
(config)# int f0/0
(config-if)# ip address 192.168.3.1 255.255.255.0
(config-if)# no shut
(config-if)# exit
(config)# ip route 0.0.0.0 0.0.0.0 192.168.3.254

now in order for the 2 hosts (PC1, PC2) to communicate between them, both of them must set default gateway IP address of the corresponding router subinterface address. (Vlan10 gateway .2.254, Vlan20 gateway 3.254).

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Three cabling systems are defined. The network access cabling system runs from the External Network Interface (ENI), where external services are onnected, to the Main Distributor (MD). The main distribution cabling system then runs to the Zone Distributor (ZD). Finally, the zone distribution cabling system runs rom the Zone Distributor (ZD) to the Equipment Outlet (EO), with the option of using a Local Distribution Point (LDP) for additional flexibility

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OSPF – Dijkstra’s Algorithm in Action

For a given source vertex (node) in the graph, the algorithm finds the path with lowest cost (i.e. the shortest path) between that vertex and every other vertex. It can also be used for finding costs of shortest paths from a single vertex to a single destination vertex by stopping the algorithm once the shortest path to the destination vertex has been determined. For example, if the vertices of the graph represent cities and edge path costs represent driving distances between pairs of cities connected by a direct road, Dijkstra’s algorithm can be used to find the shortest route between one city and all other cities. As a result, the shortest path first is widely used in network routing protocols, most notably IS-IS and OSPF (Open Shortest Path First).

Although there are many types of routing protocols, three major classes are in widespread use on IP networks:

Interior gateway routing via link-state routing protocols, such as OSPF and IS-IS
Interior gateway routing via path vector or distance vector protocols, such as RIP, IGRP and EIGRP
Exterior gateway routing. BGP v4 is the routing protocol used by the public Internet.

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Cycling 20KM Changi Beach

a retreat fascinated by the nature..

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