Serial vs Crossover

[sawquecisco]

Hi

We can connect routers with either a serial or a crossover cable. Why choose one over the other? What are their differences?

In every training video that I have watched on youtube, instructors always use serial connection between routers and it seems that serial cables use in WAN cabling. right? Why is that so, what are the advantages of serial cable over twisted pair?

Thanks.

[Reza Sharifi]

Hi,

Serial port adapters are usually used for T1,E1, T3, etc.. type of connection that provide long distance connectivity using a service provider.  For example, if you have 2 site, one is in LA and the other one is in SF and you want to use a T1 to connect theses 2 sites together, you put a T1/Serial card in each router in both locations and use service provides like Verizon, AT&T, etc to connect your sites together.  Ethernet usually is used a local area network where you connect your users to switches, routers, et... So, it is Serial vs Ethernet and not crossover.   Crossover cable is just a type of Ethernet cable to connect 2 switches together.  It is not used as much anymore since you can connect most switches together using a straight through cable.

HTH

[sawquecisco]

Thank you Reza Sharifi

It says that: "WANS are connected over serial lines and typically operate at lower speeds than LANs, and more expensive"

Serial connection is more expensive and slower than Etherrnet cable. So why do they prefer to use serial cable?

What is the secret advantage that I still can not figure out?

[darren.g]

sawquecisco wrote:
Thank you Reza Sharifi
It says that: "WANS are connected over serial lines and typically operate at lower speeds than LANs, and more expensive"
Serial connection is more expensive and slower than Etherrnet cable. So why do they prefer to use serial cable? 
What is the secret advantage that I still can not figure out?

Serial *connections* are more expensive than ethernet. Serial *interfaces* are not necessarily so.

I've noticed that most labs used for traiing are built from older or re-deployed hardware, and hence tend to be lower specification than the latest gear - and most older routers have serial ports available by default, or at least installed when theyw ere deployed because serial links were all they had.

Hence, the lab instructers use serial links because they match the ports available.

Also, consider, that serial links usually require more configuration (clocking, speed, DTE/DCE type etc), and it's more advantageous for students to see the more complex configurations than the plug-and-play type ethernet interfaces tend to be.

Cheers.

[vmiller]

To add to Rezas comments. In some lab environments you need to simulate a frame relay or serial connection for confguration purposes. Routers can act as a frame relay switch in this case.