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Why we use Trunk Port

Question : We can connect two switches via Ethernet cable why we use trunk port between switches ?

Ans:

Trunk links are required to pass VLAN information between switches. A port on a Cisco switch is either an access port or a trunk port. Access ports belong to a single VLAN and do not provide any identifying marks on the frames that are passed between switches. Access ports also carry traffic that comes from only the VLAN assigned to the port. A trunk port is by default a member of all the VLANs that exist on the switch and carry traffic for all those VLANs between the switches. To distinguish between the traffic flows, a trunk port must mark the frames with special tags as they pass between the switches. Trunking is a function that must be enabled on both sides of a link. If two switches are connected together, for example, both switch ports must be configured for trunking, and they must both be configured with the same tagging mechanism (ISL or 802.1Q).

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How many VLAN Create on Router

Ans : Vlan create on Switches not router :p

All the following information is taken from the data sheets for these devices, on the Cisco website.

The Cisco Catalyst 3550 switches support up to 1,005 VLANs.
The Cisco Cataylst 3750 switches support up to 1,005 VLANs per stack.

Both support up to 4000 VLAN IDs, but only 1,005 VLANs configured on these (some VLAN IDs will come from other switches). Unless you are a service provider, you will never configure anything like these numbers.

Please also note that the 3550 is now end-of-life, you should look at the 3560 switches instead.

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Private IP Classes Range

Public IP addresses are addresses that are valid as nodes on the Internet.
They can be resolved and routed across the Internet from one point to another.
Unlike public IP, private IP addresses are not valid on the Internet.

Three range of private IP addresses has been selected for the three network class.

For Class A network, 10.0.0.0 – 10.255.255.255 (10/8 prefix) range (For big network that requires a huge pool of 16 million private IP addresses)

For Class B network, 172.16.0.0 – 172.31.255.255 (172.16/12 prefix) range (For medium-sized network that requires 65000 private IP addresses)

For Class C network, 192.168.0.0 – 192.168.255.255 (192.168/16 prefix) range (Commonly used IP range on smaller network for easier addressing of 254 IP addresses. May not necessarily be smaller network but network managed in smaller blocks.)

private ip classes range

Beside these, there is Microsoft’s 169.254.0.0 range of default IP addresses that are allocated to systems when they are unable to obtain address from a DHCP server. Its Called APIPA

When a DHCP server fails, APIPA allocates IP addresses in the private range 169.254.0.1 to 169.254.255.254.

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What is the difference between OSPF and RIP?

RIP and OSPF are both routing protocols likely you have used without even knowing it. A routing protocol describes the way your data (or signals) get from your PC on a network to another PC or device on the network.

RIP = Hop count Algorithm

The only metric used to calculate the cost of a path (path is from point A to destination B) is the hop count from router A to router B, even if you have a path with more hops and more bandwidth available.

OSPF = Link State Algorithm

This is a more intelligent algorithm, tha build a topology of network and build the cost regarding some characteristics of path like bandwidth, load, reliability, etc.A real life example would be like when work is done and its time to drive home. You have multiple routes usually to choose from to get home. The shortest way home would obviously be a straight line from work to home. Unfortunately no magic road exists from where ever you are directly to where ever you need to go. So if you were using RIP to get home you would drive in a straight line (or take the roads that would more or less offer you a straight route home). Thing is, these roads may be BUSY, very busy in fact, you can sit in traffic for a half hour moving less than 1km sometimes. So technically the shortest way (straight line) may not be the most efficient way. Now if you were using OSPF, you would take into account traffic and other variables to decide how to get home. The quickest route home may not be the direct path, it may be a back road that has less traffic on it, through a sub division, and then to your house. However because you were using OSPF you got home quicker than if you were to use RIP as RIP didn’t really look at what the traffic was like. Now in the above paragraph turn the word “work” into “client” and the word “home” into “server” and replace the word “you” with “the packet” – magically we turn the above paragraph into tecnobabble

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