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| Tech Ranger 2004-01-11, 10:05 pm |
| Can someone please explain exactly what a Serial Interface is. I know that it is supposed to be an interface to a WAN link, but there are many WAN technologies. | |
| azimuth40 2004-01-12, 1:23 am |
| quote:
Originally posted by Tech Ranger
Can someone please explain exactly what a Serial Interface is. I know that it is supposed to be an interface to a WAN link, but there are many WAN technologies.
TR I'm guessing that you already know and are looking for validation that it is not something screwy.
Basically its the same as the serial interface in your PC com1 and com2. The WAN link is handled by the modem type. The serial interfaces on the router end are typically DB60 so that you can fan out all the full signals of a serial interface, com1 and com2 no longer do that and are async only (10 bits per byte because of start stop bits).
Com1 and Com2 use a UART Universal Asynchronous Receiver Transmitter. The DB60 serial interface uses a USART Universal Synchronous-Asynchronous Receiver Transmitter. Synchronous transmission does not use Start and Stop bits on each byte but is synch'd up with an external clock.
The router DB60 serial interface has so many pins so that it can fan out to all the common serial port signaling standards EIA/TIA-232, EIA/TIA-449, V.35, X.21, and EIA-530. This way you can hook to any modem type with external clocking from a CSU/DSU is the interface is configured as a Data Terminal Equipment (DTE) port. If it is configured as a DCE Data Communications Equipment serial interface then it supplies the clock. This allows you to hook two routers back to back with a serial interface cable for lab practice. | |
| Tech Ranger 2004-01-12, 3:51 am |
| Thank you very much for a very good explanation. | |
| Tech Ranger 2004-01-12, 9:35 am |
| I am currently studying using the cbtnuggets videos as a way to introduce myself to the basics of Cisco. I think part of my problem is that the instructor constantly refers to serial interfaces in much the same manner as he references ethernet interfaces. There is a quick mention that these interfaces are for WAN links, but he often draws diagrams making it appear that 2 routers are connected via their respective serial interfaces without anything in between. Would I be correct to assume that serial interfaces are never used to directly connect one router to another except for educational purposes? Am I also correct to assume that if you did connect 2 routers together this way, you would encapsulate using PPP?
Also, what kind of cabling is used to connect to serial interfaces? Is DB60 only for HSSI? | |
| dmaftei 2004-01-15, 9:27 am |
| quote:
Originally posted by Tech Ranger
Would I be correct to assume that serial interfaces are never used to directly connect one router to another except for educational purposes?
I wouldn't say 'never', but I think it's quite rare to find back-to-back routers in production networks.
quote:
Am I also correct to assume that if you did connect 2 routers together this way, you would encapsulate using PPP?
Nope; you can use other protocols too.
quote:
Also, what kind of cabling is used to connect to serial interfaces?
Expensive serial cables. | |
| ClintonN 2004-01-15, 2:20 pm |
| How are the CBT nuggets for cisco? | |
| Tech Ranger 2004-01-15, 9:02 pm |
| quote:
Originally posted by ClintonN
How are the CBT nuggets for cisco?
For a beginner like me, they're great. | |
| Boulware5 2004-01-15, 9:59 pm |
| I just checked out the CBT site and they are giving away free videos for a bunch of exams and topic, including Cisco IOS Basics and Intro to the OSI Reference Model. Are these really full videos or because it's free is it like 10 minutes long and after that it shuts off because they want you to buy it? | |
| Tech Ranger 2004-01-16, 12:56 am |
| quote:
Originally posted by Boulware5
I just checked out the CBT site and they are giving away free videos for a bunch of exams and topic, including Cisco IOS Basics and Intro to the OSI Reference Model. Are these really full videos or because it's free is it like 10 minutes long and after that it shuts off because they want you to buy it?
Each course consists of a series of videos. Each video is usually about 30 minutes. The free videos are complete. They are individual videos, not complete courses. You can watch them online. I have learned a lot from the free videos. |
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