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).

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.

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.