2014年2月24日星期一

The Performance / Throughput of Cisco Switch


For example, WS-C2960S-24TD-L is 13.3 Mpps.

The figure MPPS expresses the maximum number of frames per second that can be processed by the device. It is not dependent on frame size but clearly small frames require higher packet rates.

To give you an idea of what this number says:
smallest frames in Ethernet are 64 bytes in size, taking in account the preamble (8 bytes) and the minimum inter-frame gap (the last two counts roughly for 20.2 bytes) to fill a GE port in one direction you need 1484560 frame per second.

10^9 / [(64+20.2)*8] where 8 is bits/byte.

So a number of 13.3 MPPS is equivalent to [((13.3 M * (64+20.2) * 8)) / 10^9 = 8.95 / 2=4.47] 4.47 GE ports filled with smallest frames bidirectional.

On the other hand frames of max size 1518 bytes require 81264 fps to fill a GE port in one direction.

So this number expresses the forwarding capability of the device.

A non blocking device with 48 GE ports WS-C2960S-48TD-L would require 2 * 1484560 * 48 as MPPS or higher.

Therefore the performance of a device will be determined by combination of number of packets per sec and the size of the packet.


More related: Cisco 1941 thoughout

2014年1月16日星期四

Catalyst 3750 SFP Transceiver

I am trying to figure which port is fiber sfp and which port is copper sfp. I have a 3750 12s-s.

...
Gi1/0/5                      connected    trunk      a-full a-1000 unsupported
Gi1/0/9                      connected    trunk      a-full a-1000 1000BaseSX SFP
Gi1/0/10                      connected   1          a-full a-1000 10/100/1000BaseTX SFP
Gi1/0/11                    connected    1          a-full a-1000 10/100/1000BaseTX SFP

I know that gig1/0/5 is a non-Cisco sfp sx transceiver
I am not sure about gig1/0/9-gig1/0/11. Is that a copper sfp transceiver? If yes, then is then an actual sfp transceiver in there?

The answer:
Gig1/0/9 is a fiber SX transceiver
Gig1/0/10 - 11 are copper transceivers


Yes they are actually there otherwise the ports would not show anything.

The Cisco SFP products you maybe interested, please visit the links below:

2014年1月9日星期四

Wireless / Wired Access Point Advice

I have a friend who I set up a video security system for in his small business.  His cable internet comes in on the top floor and that is where is router is installed.  He uses it for about 4 devices on the top floor, some wired and some wireless.

He wants to install a computer and a wireless Point of Sales terminal on the ground floor shop.  The wireless signal is sketchy by the time you get to the ground floor.  I was thinking of installing an access point for him.  I am unable to find the specs I am looking for, but think that maybe they are just advertising the products the wrong way.

So here is what I need.
A Wireless access point that offers wifi extender type services.  Meaning that is should extend the same network not create a new one (like connecting a wireless router would do).  I can not have double netting, it will break the security system.

I need it to have at least two wired switch ports that again, will only be switching, not routing (NO DOUBLE NAT).
I would like to spend as little as possible but get something decent.  Maybe the $50 - $100 range.

The advice:
1 If you cannot easily get a wired Ethernet cable to the ground floor, I suggest you get two powerline adapters (Ethernet outlets) and put one on the top floor and one on the ground floor.
Now on the ground floor put in a switch that will allow you to connect your POS to the network on the same subnet.
I assume your POS is best wired, but with the above setup you can easily add a wireless router on the same subnet and network as the top floor.


2 Perhaps this diagram will help.

* Always* use Ethernet cable to connect when you can.
I can't emphasize this enough.
If routing some Ethernet cable isn't included in your price range then do seriously consider it.  The cable is cheap enough.

A commodity wireless router can do what you want in your price range.  Take a look at the attached diagram.

As mentioned, power line extenders are a userful substitute for Ethernet cable.

Never run QuickBooks shared over wireless.  Sometimes it may work and at some point may fail miserably and then you'll have a very hard time figuring out why.  You won't believe it's the wireless as the messages you get suggest corrupted files, etc.

The idea of centralizing wireless "radios" is a good one.  There are lots of factors and you may find that multiples are better than just one - as you have been pursuing.  Walls (particularly outside walls), ceilings and floors all attenuate the signals.  2 or 3 of them at most is about the limit.  None is best of course.  1 is usually OK.  2 is often OK.  Distance matters too but less so unless walls, etc. get in the way anyway.  It's hard to get coverage from one end of a large building space to the other end and hard to go from one floor to another unless the path is rather immediate above or below.

One easy way to find out is this:
Take a wireless router or access point around the building, plugging it into power as you go.  Then, while it's in one place, survey the result.  It doesn't need to have a connection to anything in order to test the wireless coverage.  Use something like NetStumbler to get signal levels on a laptop and walk around.

But, first, try hard to run a cable from the 3rd floor to the 1st floor.  That will resolve more problems than you might imagine!!

Some switch recommend for you, maybe you need them when connect the wireless / wired access point:

2013年12月30日星期一

How to Configurate NAT on Cisco 1941


There are two types of NAT that can be configured on a Cisco router Cisco 3925E; static, and dynamic.

Static NAT Configuration:
 This type is used when you want to do one-to-one assignment of local IP addresses to global IP addresses.
 1. Establish static translation between an inside local address and an inside global address,
 Router(config)#ip nat inside source static XXX.XXX.XXX.XXX YYY.YYY.YYY.YYY
 where,
 XXX.XXX.XXX.XXX is the (inside) local address
 YYY.YYY.YYY.YYY is the (inside) global address

2. Specify the local interface. This is done by going to the interface configuration mode and issuing,
 Router(config-if)#ip nat inside

3. Specify the global address. This is done by going to the interface configuration mode and issuing,
 Router(config-if)#ip nat outside

Dynamic NAT Configuration:
 This type is used when you want the router to do the mapping dynamically. This method is useful when you have too many global and local addresses and you do not want to do the mapping manually, or when the number of global addresses available is less than the local addresses.
This would lead us to two different scenarios,
A. The number of global IP addresses is equal or less than the local addresses and more than one. (global >= local >1)
1. Define a pool of global addresses that would be employed in the translation,
Router(config)#ip nat pool NAME XXX.XXX.XXX.XXX YYY.YYY.YYY.YYY netmask ZZZ.ZZZ.ZZZ.ZZZ
where,
NAME is the name of the pool
XXX.XXX.XXX.XXX is the starting IP address of the pool
YYY.YYY.YYY.YYY is the end IP address of the pool
ZZZ.ZZZ.ZZZ.ZZZ is the subnet mask of the network that the pool is part of.

Below are the details for the Cisco 1941 NAT configuration:
<iframe width="420" height="315" src="//www.youtube-nocookie.com/embed/Rs2tN6kAinU" frameborder="0" allowfullscreen></iframe>

http://www.youtube.com/watch?v=Rs2tN6kAinU


It is refered from: www.routergeek.net/general.

2013年12月17日星期二

How to Password Recovery for the Cisco 2900

There are no specific requirements for recovery passwprd for the Cisco 2900, taking Cisco 2921 router and Cisco 2951 router for examples

The steps:
1 Either switch off or shut down the router.

2 Remove the compact flash that is on the rear of the router. This image shows the rear of the 2951 router:

For more information, refer to Back Panel Slots and Connectors on the Cisco 2921 and 2951 Routers.
3 Switch on the router.

4 Once the router is on Rommon mode, reinsert the compact flash.

5 Type confreg 0x2142 at the rommon 1> prompt in order to boot from Flash.
This step bypasses the startup configuration where the passwords are stored.

6 Type reset at the rommon 2> prompt.
The router reboots, but ignores the saved configuration.

7 Type no after each setup question, or press Ctrl-C in order to skip the initial setup procedure.

8 Type enable at the Router> prompt.
You are in enable mode and should see the Router# prompt.

9 Type configure memory or copy startup-config running-config in order to copy the nonvolatile RAM (NVRAM) into memory.
Warning:  Do not enter copy running-config startup-config or write. These commands erase your startup configuration.

10 Issue the show running-config command.
The show running-config command shows the configuration of the router. In this configuration, the shutdown command appears under all interfaces, which indicates all interfaces are currently shut down. In addition, the passwords (enable password, enable secret, vty, and console passwords) are in either an encrypted or unencrypted format. You can reuse unencrypted passwords. You must change encrypted passwords to a new password.
11 Type configure terminal.
The hostname(config)# prompt appears.

12 Type enable secret <password> in order to change the enable secret password. For example:
hostname(config)#enable secret cisco

13 Issue the no shutdown command on every interface that you use.
If you issue a show ip interface brief command, every interface that you want to use should display up up.

14 Type config-register <configuration_register_setting> . Where <configuration_register_setting> is either the value you recorded in step 2 or 0x2102 . For example:
hostname(config)#config-register 0x2102

15 Press Ctrl-z or end in order to leave the configuration mode.
The hostname# prompt appears.

16 Type write memory or copy running-config startup-config in order to commit the changes.
The Cisco 2951 price and Cisco 1921 price, please refer the below links:
http://www.3anetwork.com/cisco-cisco2951/k9-price_p240.html
http://www.3anetwork.com/cisco-cisco1921-sec/k9-price_p210.html

2013年12月16日星期一

Cisco Router Question: Cisco 2901

Question: I've logged into a Cisco 2901 and typed 'show ip route'. And it says something like this:
192.168.10.0/24 directly connected to fastethernet0/0
192.168.9.0/24 directly connected fastethernet0/0
I don't fully understand what the above means?


Answer: It means those routers are derived from the IP address/mask of your interfaces and are automatically generated.
The router is connected, and can reach, two different LANs (or networks).  192.168.10 and .9 IPv4.
You router interface f0/0 is configured for  seconday ip addresses
Ip address x.x.x.x y.y.y.y secondary

The more infornation or overview of Cisco router, please visit: http://ciscorouteroverview.tumblr.com

2013年11月26日星期二

Problems HWIC-3G-GSM for Cisco 1941 router

I am replacing an old 1841 that has a HWIC-3G-GSM coax card in it
I need to know what is the part number for the equivalent HWIC-3G card that goes into the new Cisco 1941 router.
Does anyone know what that part number is?  (and could you please provide both a link and a picture so that I can be sure it is the coax version?)

The 1841 also has a T-1 WIC so if you could also include the part number for an equivalent T-1 WIC for the Cisco 1941 router, I would appreciate it.

The solution:
The part numbers vary based upon the carrier.
EHWIC-3G-HSPA +7-A    :  GSM card for AT&T
3.7G HSPA+ Release 7 EHWIC w/ SMS/GPS (MC8705) (AT&T)

EHWIC-3G-EVDO-S : GSM card for Sprint
3G EHWIC Sprint EV-DO Rev A/0/1xRTT 800/1900MHz with SMS/GPS

EHWIC-3G-EVDO-V: GSM card for Verizon
3G EHWIC Verizon EV-DO Rev A/0/1xRTT 800/1900MHz w/ SMS/GPS

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