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Showing posts with the label Switching

Configuring DHCP Server

What is DHCP? The DHCP (Dynamic Host Configuration Protocol) is an Internet protocol responsible for automating the configuration of computers which use TCP/IP. DHCP can be used to assign IP addresses to computers by delivering TCP/IP configuration addresses such as IP address, subnet masks, default routers and DNS addresses. It can also be used to provide information for a number of other services such as printers, time, news and TFTP servers. Config A Cisco router can be configured as a DHCP server to assign IP addresses. The range of IP addresses which can be given out is called a 'pool'. From this pool clients are leased addresses for a given time, after which the lease expires and the client needs to request a new IP address lease. The following config lines show how to setup a DHCP pool of addresses in the 192.168.0.0 IP range: no ip dhcp conflict logging ip dhcp excluded-address 192.168.0.1 192.168.0.50 ! ip dhcp pool 1 network 192.168.0.0 255.255.255.0 default-route

Switching - Introducing Spanning Tree Protocol (STP)

A loop avoidance mechanism called STP has been developed to alleviate the 3 issues above. There are two varieties of Spanning Tree Protcol, STP (802.1d) and RSTP ('Rapid' 802.1w) both work in a similar way. A Spanning Tree Algorithm examines the switched network, and, through a series of decisions (discussed below) places each port in the loop into either Forwarding or Blocking state, therefore breaking the loop. Types of port in STP: Designated Port (DP) Closest to Root i.e. All Ports on the Root Switch. Route Port (RP) One Per Switch. Blocking Port. The process the switches go through to decide which port they place in blocking or forwarding state is governed by the position of a 'Root Switch' (also known as 'Root Bridge'): To decide which switch is the root switch, each switch begins by claiming to be the Root Switch they all send out an STP messages called BPDU's (Bridge Protocol Data Unit). A fight-off happens to determine the fi

Switching - Switched Networks with Virtual LAN?

VLAN's (Virtual Local Area Networks) are a way to structure a network logically; put simply a VLAN is a collection of nodes which are grouped together in a single broadcast domain (address range) that is based on something other than physical location. If a host in a particular VLAN sends a message to a switch it will only forward the message to hosts within the same VLAN. Another way to think of VLAN's is to think that when you split a switch into 2 VLAN's and assign half the ports to VLAN 1 and the other half to VLAN 2, this is the same as if it was two totally separate unlinked switches. A switches internal TCP/IP software resides in VLAN 1 By default all ports belong to VLAN 1 Different VLAN's would also be different broadcast domains VLAN Trunking If you have two switches with VLAN's configured on both you could link the VLANs on individually but this means you need lots of cables and take up lots of switch ports: or You could use 1 cable and one port on e

Switching - Configuring VLAN?

To setup 2 switches with VLAN's 4 and 5 and link with a trunk in 802.1q mode, for example: conf t  vlan 4 name jim  vlan 5 name claire  int fa0/1  switchport access vlan 4  int fa0/2  switchport access vlan 5  int fa0/11  switchport mode trunk  switchport trunk encapsulation dot1q  exit On older IOS: vlan database vlan 4 name jim vlan 5 name claire exit To view VLAN's use "sh vlan". note: In the example above if Switch 1 is in VTP server mode and switch 2 in client mode, the VLAN information shoud be transmitted on the trunk and appear on switch 2.