As any good web developer knows, a web developer is always worried about creating the best web site that they can. They work very hard with the client to decide exactly how they want their site to look, to function, and also how to make it run the most efficiently. These are all things that people need to think about when they are creating a web site, but sometimes we forget one of the most important things, how are we going to get our site on the internet?
No matter how great the web site you create is, it is meaningless if you do not get it out on the internet. So if you are going to get our web site on the internet, then you can either host it on a web server yourself, or get a web hosting company to host it for you. If you are a large company that has an IT staff to setup the infrastructure to host a web site, then this is probably the best idea, because you have more control over the things that happen.
However, most people that create web sites do not have the money or the time to setup such an infrastructure. These people will have to get a web hosting company to host their web site. Here are a few things to consider when you try to pick a web hosting company that is right for you:
Space – Some web hosting companies offer more space than others. If you are going to create a large web site, or you are looking to expand a lot in the near future, then the amount of space offered is very important.
Email Addresses – If your web site is going to give away email addresses, or you need extra email addresses for your users, then the amount of free email addresses that you are given might be very important.
Database Access – Some web hosting companies offer the ability to use a MySQL or SQL Server database to store information or authenticate against. This can be a very important fact to help make your web site more secure, or more dynamic.
Showing posts with label host. Show all posts
Showing posts with label host. Show all posts
Wednesday, December 31, 2008
Thursday, December 25, 2008
Cisco CCNP / BCMSN Exam Tutorial: Static VLANs
BCMSN exam success and earning your CCNP certification requires you to add to your knowledge of VLAN configuration. When you studied for your CCNA exam, you learned how to place ports into a VLAN and what the purpose of VLANs was, but you may not be aware that there are two types of VLAN membership. To pass the BCMSN exam, you must know the details of both types.
In this tutorial, we'll take a look at the VLAN type you are most familiar with, the "static VLAN". As you know, VLANs are a great way to create smaller broadcast domains in your network. Host devices connected to a port belonging to one VLAN will receive broadcasts and multicasts only if they were originated by another host in that same VLAN. The drawback is that without the help of a Layer 3 switch or a router, inter-VLAN communication cannot occur.
The actual configuration of a static VLAN is simple enough. In this example, by placing switch ports 0/1 and 0/2 into VLAN 12, the only broadcasts and multicasts hosts connected to those ports will receive are the ones transmitted by ports in VLAN 12.
SW1(config)#int fast 0/1
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 12
% Access VLAN does not exist. Creating vlan 12
SW1(config-if)#int fast 0/2
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 12
One of the many things I love about Cisco switches and routers is that if you have forgotten to do something, the Cisco device is generally going to remind you or in this case actually do it for you. I placed port 0/1 into a VLAN that did not yet exist, so the switch created it for me!
There are two commands needed to place a port into a VLAN. By default, these ports are running in dynamic desirable trunking mode, meaning that the port is actively attempting to form a trunk with a remote switch in order to send traffic between the two switches. The problem is that a trunk port belongs to all VLANs by default, and we want to put this port into a single VLAN only. To do so, we run the switchport mode access command to make the port an access port, and access ports belong to one and only one VLAN. After doing that, we placed the port into VLAN 12 with the switchport access vlan 12 command. Running the switchport mode access command effectively turns trunking off on that port.
The hosts are unaware of VLANs; they simply assume the VLAN membership of the port they're connected to. But that's not quite the case with dynamic VLANs, which we'll examine in the next part of this BCMSN tutorial.
In this tutorial, we'll take a look at the VLAN type you are most familiar with, the "static VLAN". As you know, VLANs are a great way to create smaller broadcast domains in your network. Host devices connected to a port belonging to one VLAN will receive broadcasts and multicasts only if they were originated by another host in that same VLAN. The drawback is that without the help of a Layer 3 switch or a router, inter-VLAN communication cannot occur.
The actual configuration of a static VLAN is simple enough. In this example, by placing switch ports 0/1 and 0/2 into VLAN 12, the only broadcasts and multicasts hosts connected to those ports will receive are the ones transmitted by ports in VLAN 12.
SW1(config)#int fast 0/1
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 12
% Access VLAN does not exist. Creating vlan 12
SW1(config-if)#int fast 0/2
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 12
One of the many things I love about Cisco switches and routers is that if you have forgotten to do something, the Cisco device is generally going to remind you or in this case actually do it for you. I placed port 0/1 into a VLAN that did not yet exist, so the switch created it for me!
There are two commands needed to place a port into a VLAN. By default, these ports are running in dynamic desirable trunking mode, meaning that the port is actively attempting to form a trunk with a remote switch in order to send traffic between the two switches. The problem is that a trunk port belongs to all VLANs by default, and we want to put this port into a single VLAN only. To do so, we run the switchport mode access command to make the port an access port, and access ports belong to one and only one VLAN. After doing that, we placed the port into VLAN 12 with the switchport access vlan 12 command. Running the switchport mode access command effectively turns trunking off on that port.
The hosts are unaware of VLANs; they simply assume the VLAN membership of the port they're connected to. But that's not quite the case with dynamic VLANs, which we'll examine in the next part of this BCMSN tutorial.
Cisco CCNP / BCMSN Exam Tutorial: Dynamic VLANs and VMPS
Knowledge of Dynamic VLANs and VMPS is important in your efforts to pass the BCMSN exam and earn your CCNP, and it's also a great skill to have for your networking career.
As a CCNA and CCNP candidate, you know how and why to configure static VLANs. Static VLANs can be a powerful tool for reducing unnecessary broadcast and multicast traffic, but if hosts are moved from one switch port to another, you've got to make those changes manually on the switch. With Dynamic VLANs, the changes are made - how else? - dynamically.
The actual configuration of dynamic VLANs is out of the scope of the BCMSN exam, but as a CCNP candidate you need to know the basics of VMPS - a VLAN Membership Policy Server.
Using VMPS results in port VLAN membership changes being performed dynamically, because the port's VLAN membership is decided by the source MAC address of the device connected to that port. (Yet another reason that the first value a switch looks at on an incoming frame is the source MAC address.)
In my home lab network, I've got a host connected to switch port fast0/1 that resides in VLAN 12. What if we had to move Host 1's connection to the switch to port 0/6? With static VLANs, we'd have to connect to the switch, configure the port as an access port, and then place the port into VLAN 12. With VMPS, the only thing we'd have to do is reconnect the cable to port 0/6, and the VMPS would dynamically place that port into VLAN 12.
I urge you to do additional reading regarding VMPS. Use your favorite search engine for the term configuring vmps and you'll quickly find some great official Cisco documentation on this topic.
To review, the VLAN membership of a host is decided by one of two factors. With static VLANs, the host's VLAN membership is the VLAN to which its switch port has been assigned. With dynamic VLANs, it is dependent upon the host's MAC address.
As a CCNA and CCNP candidate, you know how and why to configure static VLANs. Static VLANs can be a powerful tool for reducing unnecessary broadcast and multicast traffic, but if hosts are moved from one switch port to another, you've got to make those changes manually on the switch. With Dynamic VLANs, the changes are made - how else? - dynamically.
The actual configuration of dynamic VLANs is out of the scope of the BCMSN exam, but as a CCNP candidate you need to know the basics of VMPS - a VLAN Membership Policy Server.
Using VMPS results in port VLAN membership changes being performed dynamically, because the port's VLAN membership is decided by the source MAC address of the device connected to that port. (Yet another reason that the first value a switch looks at on an incoming frame is the source MAC address.)
In my home lab network, I've got a host connected to switch port fast0/1 that resides in VLAN 12. What if we had to move Host 1's connection to the switch to port 0/6? With static VLANs, we'd have to connect to the switch, configure the port as an access port, and then place the port into VLAN 12. With VMPS, the only thing we'd have to do is reconnect the cable to port 0/6, and the VMPS would dynamically place that port into VLAN 12.
I urge you to do additional reading regarding VMPS. Use your favorite search engine for the term configuring vmps and you'll quickly find some great official Cisco documentation on this topic.
To review, the VLAN membership of a host is decided by one of two factors. With static VLANs, the host's VLAN membership is the VLAN to which its switch port has been assigned. With dynamic VLANs, it is dependent upon the host's MAC address.
Wednesday, December 24, 2008
Cisco CCNA Certification Exam Tutorial: Access List Details You Must Know!
To pass the CCNA exam, you have to be able to write and troubleshoot access lists. As you climb the ladder toward the CCNP and CCIE, you'll see more and more uses for ACLs. Therefore, you had better know the basics!
The use of "host" and "any" confuses some newcomers to ACLs, so let's take a look at that first.
It is acceptable to configure a wildcard mask of all ones or all zeroes. A wildcard mask of 0.0.0.0 means the address specified in the ACL line must be matched exactly a wildcard mask of 255.255.255.255 means that all addresses will match the line.
Wildcard masks have the option of using the word host to represent a wildcard mask of 0.0.0.0. Consider a configuration where only packets from IP source 10.1.1.1 should be allowed and all other packets denied. The following ACLs both do that.
R3#conf t
R3(config)#access-list 6 permit 10.1.1.1 0.0.0.0
R3(config)#conf t
R3(config)#access-list 7 permit host 10.1.1.1
The keyword any can be used to represent a wildcard mask of 255.255.255.255.
R3(config)#access-list 15 permit any
Another often overlooked detail is the order of the lines in an ACL. Even in a two- or three-line ACL, the order of the lines in an ACL is vital.
Consider a situation where packets sourced from 172.18.18.0 /24 will be denied, but all others will be permitted. The following ACL would do that.
R3#conf t
R3(config)#access-list 15 deny 172.18.18.0 0.0.0.255
R3(config)#access-list 15 permit any
The previous example also illustrates the importance of configuring the ACL with the lines in the correct order to get the desired results. What would be the result if the lines were reversed?
R3#conf t
R3(config)#access-list 15 permit any
R3(config)#access-list 15 deny 172.18.18.0 0.0.0.255
If the lines were reversed, traffic from 172.18.18.0 /24 would be matched against the first line of the ACL. The first line is “permit any", meaning all traffic is permitted. The traffic from 172.18.18.0/24 matches that line, the traffic is permitted, and the ACL stops running. The statement denying the traffic from 172.18.18.0 is never run.
The key to writing and troubleshoot access lists is to take just an extra moment to read it over and make sure it's going to do what you intend it to do. It's better to realize your mistake on paper instead of once the ACL's been applied to an interface!
The use of "host" and "any" confuses some newcomers to ACLs, so let's take a look at that first.
It is acceptable to configure a wildcard mask of all ones or all zeroes. A wildcard mask of 0.0.0.0 means the address specified in the ACL line must be matched exactly a wildcard mask of 255.255.255.255 means that all addresses will match the line.
Wildcard masks have the option of using the word host to represent a wildcard mask of 0.0.0.0. Consider a configuration where only packets from IP source 10.1.1.1 should be allowed and all other packets denied. The following ACLs both do that.
R3#conf t
R3(config)#access-list 6 permit 10.1.1.1 0.0.0.0
R3(config)#conf t
R3(config)#access-list 7 permit host 10.1.1.1
The keyword any can be used to represent a wildcard mask of 255.255.255.255.
R3(config)#access-list 15 permit any
Another often overlooked detail is the order of the lines in an ACL. Even in a two- or three-line ACL, the order of the lines in an ACL is vital.
Consider a situation where packets sourced from 172.18.18.0 /24 will be denied, but all others will be permitted. The following ACL would do that.
R3#conf t
R3(config)#access-list 15 deny 172.18.18.0 0.0.0.255
R3(config)#access-list 15 permit any
The previous example also illustrates the importance of configuring the ACL with the lines in the correct order to get the desired results. What would be the result if the lines were reversed?
R3#conf t
R3(config)#access-list 15 permit any
R3(config)#access-list 15 deny 172.18.18.0 0.0.0.255
If the lines were reversed, traffic from 172.18.18.0 /24 would be matched against the first line of the ACL. The first line is “permit any", meaning all traffic is permitted. The traffic from 172.18.18.0/24 matches that line, the traffic is permitted, and the ACL stops running. The statement denying the traffic from 172.18.18.0 is never run.
The key to writing and troubleshoot access lists is to take just an extra moment to read it over and make sure it's going to do what you intend it to do. It's better to realize your mistake on paper instead of once the ACL's been applied to an interface!
Cisco CCNA Certification: Static Routing Tutorial
In studying for your CCNA exam and preparing to earn this valuable certification, you may be tempted to spend little time studying static routing and head right for the more exciting dynamic routing protocols like RIP, EIGRP, and OSPF. This is an understandable mistake, but still a mistake. Static routing is not complicated, but it's an important topic on the CCNA exam and a valuable skill for real-world networking.
To create static routes on a Cisco router, you use the ip route command followed by the destination network, network mask, and either the next-hop IP address or the local exit interface. It's vital to keep that last part in mind - you're either configuring the IP address of the downstream router, or the interface on the local router that will serve as the exit interface.
Let's say your local router has a serial0 interface with an IP address of 200.1.1.1/30, and the downstream router that will be the next hop will receive packets on its serial1 interface with an IP address of 200.1.1.2/30. The static route will be for packets destined for the 172.10.1.0 network. Either of the following ip route statements would be correct.
R1(config)#ip route 172.10.1.0 255.255.255.0 200.1.1.2 (next-hop IP address)
OR
R1(config)#ip route 172.10.1.0 255.255.255.0 serial0 ( local exit interface)
You can also write a static route that matches only one destination. This is a host route, and has 255.255.255.255 for a mask. If the above static routes should only be used to send packets to 172.10.1.1., the following commands would do the job.
R1(config)#ip route 172.10.1.1 255.255.255.255 200.1.1.2 (next-hop IP address)
OR
R1(config)#ip route 172.10.1.1 255.255.255.255 serial0 ( local exit interface)
Finally, a default static route serves as a gateway of last resort. If there are no matches for a destination in the routing table, the default route will be used. Default routes use all zeroes for both the destination and mask, and again a next-hop IP address or local exit interface can be used.
R1(config)#ip route 0.0.0.0 0.0.0.0 200.1.1.2 (next-hop IP address)
OR
R1(config)#ip route 0.0.0.0 0.0.0.0 serial0 ( local exit interface)
IP route statements seem simple enough, but the details regarding the next-hop IP address, the local exit interface, default static routes, and the syntax of the command are vital for success on CCNA exam day and in the real world.
To create static routes on a Cisco router, you use the ip route command followed by the destination network, network mask, and either the next-hop IP address or the local exit interface. It's vital to keep that last part in mind - you're either configuring the IP address of the downstream router, or the interface on the local router that will serve as the exit interface.
Let's say your local router has a serial0 interface with an IP address of 200.1.1.1/30, and the downstream router that will be the next hop will receive packets on its serial1 interface with an IP address of 200.1.1.2/30. The static route will be for packets destined for the 172.10.1.0 network. Either of the following ip route statements would be correct.
R1(config)#ip route 172.10.1.0 255.255.255.0 200.1.1.2 (next-hop IP address)
OR
R1(config)#ip route 172.10.1.0 255.255.255.0 serial0 ( local exit interface)
You can also write a static route that matches only one destination. This is a host route, and has 255.255.255.255 for a mask. If the above static routes should only be used to send packets to 172.10.1.1., the following commands would do the job.
R1(config)#ip route 172.10.1.1 255.255.255.255 200.1.1.2 (next-hop IP address)
OR
R1(config)#ip route 172.10.1.1 255.255.255.255 serial0 ( local exit interface)
Finally, a default static route serves as a gateway of last resort. If there are no matches for a destination in the routing table, the default route will be used. Default routes use all zeroes for both the destination and mask, and again a next-hop IP address or local exit interface can be used.
R1(config)#ip route 0.0.0.0 0.0.0.0 200.1.1.2 (next-hop IP address)
OR
R1(config)#ip route 0.0.0.0 0.0.0.0 serial0 ( local exit interface)
IP route statements seem simple enough, but the details regarding the next-hop IP address, the local exit interface, default static routes, and the syntax of the command are vital for success on CCNA exam day and in the real world.
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