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Chủ Nhật, 20 tháng 3, 2011

Lựa chọn thiết bị cho cisco lab

Most of us think them, but many of us don't finish. Spend more time with the kids. Lose weight. Watch less TV.
IOS: Ignoring the legality, you can download software from if you have a login that shows you as having at least 1 device under maintenance.
Thiết bị:
+ Cisco 2500
1 ethernet (10Mbps) -> non-XM doesn't support LAN trunking
IOS can run IOS 12.3
Physical ethernet interface use DB-15 connector-> need equiring an external transceiver ($10)
Dynagen simulator+ real switch = lab
The other good thing about 2520's, no transciever required, although they still support them. 2520's are the only 2500's that I'm aware of with a built in RJ-45 10BaseT port.
And finally, the piece of equipment you absolutely must have is a Cisco 2511 Terminal Server. If you have more than 3 pieces of equipment, you are going to go crazy without it! :)
+ Cisco 2600
Of note, the non-XM routers had 10 Mbps Ethernet interfaces and no support for LAN trunking, while the XMs have 100 Mbps FastEthernet interfaces and do support LAN trunking.
Like 2500's, 2600's (both types) can run up through 12.3 mainline IOS
2600xms couldn't function as MPLS PE but can run IOS 12.5
While the 261x (2610, 2611) models don't have FastEthernet (10/100), the 262x (2620, 2621) models *DO* have FastEthernet.
The 2620 non-XM has one FastEthernet port and the 2621 has two FastEthernet ports. They are supports trunking but expensive (6-700$) (see Table 1-1 on this document at Cisco.COM support trunking but must upgrade IOS to 12.2 + IP Plus or higher
2610, 2611, 2612 lastest IOS support inter VLAN trunking (only 802.1q) + MPLS but not IPv6
--> 2650xm, 2691 best choice

+ Cisco 1800
1841 is the least expensive 1800 series router that supports WIC slots,
Also, 1800's support more features, and all the latest IOS versions.
1841 support MPLS, can use old WIC card and FE: fast Ethernet

+ Cisco 3640:
3620 can run IOS up to 12.3 -> ignore it. 3640 support lastest version of IOS (2008)
3640's are a bit larger (2 rack units) compared to the other 1 RU routers we've looked at here. 3640's have 4 network module slots, and were often used for WAN aggregation in production networks. However, the used market has lots of inventory, keeping the price down. A quick peek at EBay shows plenty for sale that also have max memory of 128M RAM and 32 M flash, at around $200. However, the 3640 chassis only has 4 network module slots, with no fixed LAN interfaces or WIC slots. Translated, you have to buy at least 1 network module, or 2, to get at least one LAN interface and one WIC slot. For example, you could get a NM-1FE2W, which include 1 FastE interface and 2 WIC slots. Once you buy the router and NM-1FE2W, you need a few serial interfaces, so you can buy the same WIC-2T that you would have bought for the 2600's or 1841's.
NM-2E2W (cheap choice)
Buying Tip: Buy the router with max RAM/flash already installed. For example
Model       RAM/Flash
3640:        128/32
2501:        16/16
2610:        64/16
2620:        64/32
2610XM:   256/48
1841:        384/128

Anyone that's made it past the first few hours of CCNA study, or used a Cisco router, knows that Cisco routers run IOS, more formally known as "Cisco IOS Software". However, if you've not worked with routers on a regular basis, it's sometimes scary to pull the trigger to buy some used gear for a home lab. I'll address some of the issues related to choosing an IOS today, and how figure out the amount of flash and RAM needed to support each IOS.

First, a quick overview. Today, IOS for the router models you'd use in a CCNA or CCNP lab ships as a single compiled file. Cisco builds different IOS images (files) based on the model of router and the feature set, as well as different images for each maintenance level (version and release).
The IOS feature set determines what commands and functions that IOS supports - the more functions in the IOS image, the more it costs, and the more RAM and flash required when using it. The best way to figure out what features are in each feature set is to use the Cisco Feature Navigator, where you can select features from a list, and then find out what router models support it, in which IOS versions. It also displays the amount of flash and RAM needed for each version.
Latest  Cisco IOS Release on  March 2011 is 12.4(16)MR
+ Choosing router for CCNP (Good prep for CCNP next, without going overboard)

First, my suggested topology for options 2 and 3 are the same - three routers, with a need for 2 serial and 1 LAN interface per router. The following figure shows the basics, and how I'd probably leave it cabled most of the time - ignoring the switches for the time being.
So, to be complete, here's the part list for option 3:
* 1 2610 non-XM router ($100), or 1841 ($650)
* 1 2520 router ($125)
* 1 3640, WIC-2T, NM-1FE2W ($400)
* 1 back-back serial (Smart serial) cable ($10)
* 2 back-back serial (DB-60/Smart serial) cables ($20)
* 1 console cable (free with router probably)
* 3 AC power cables (free with router probably)
* 3 Ethernet cables (crossovers, if using as shown in the following figure) ($30)
The total cost is $1235 (with 1841, option 3B). Option 3B: $1235 (replaces 2610 non-XM with still-production 1841, with 2 routers running the latest IOS versions)

+ Choosing switch:

On routers, if you run IOS on 5 different models of routers, the commands used to configure and examine a particular feature act the same, with the same syntax, with only minor exceptions to that rule. That makes studying router topics for the exams easier, and it makes writing exam questions easier, because the syntax and show command output should be the same across routers.
Most of Cisco's switch product line runs IOS - not the exact same IOS that runs on routers, but an OS whose user interface acts like router IOS. There are slight differences in command syntax on some models of IOS switches, and in defaults for commands - and that poses a bit of a problem for exam preparation and for the people writing the exam questions. If they write a question whose answer might be different depending on the model of switch, then they'd have to tell us all that the exam is based on a particular model series of switches.
-> Best choice is 2950 /w enhanced image or 3500
But make sure at least one of them is a 2950. It's worth the extra money to have a switch model (2950) that's so similar to the current models.
for CCNP, the 2 x 2950/2960 and 2 X 3550/3560 would be a nice place to start. The 3500's are more powerful that 2900's, but they run the same software, with the same command syntax, so for CCNA exam prep, there's no real benefit to the 3500 over the 2900.
Both the 2950 and 3550 switches run two major IOS options - a standard image and enhanced image. The 2950 series switches cannot be upgraded to the enhanced image, so that choice is a buy-time decision. The 3550's can be field upgraded
The 2900 XL series has some significant benefits for CCNA exam prep compared to 1900's. The commands match up better with 2960 command syntax compared to 1900s - generally, the same base command is used on the 2900XLs as on the 2960's. It supports trunking (both types), so it can trunk using 802.1Q with 2960's or 2950's in case you get one of the more recent switches. (2950's and 2960's only support 802.1Q, which is fine for real life.) On the con side for 2900 XL's, the parameters on commands supported on the 2900's and 2960's differ, in part due to the different features supported. So, you can learn the concepts behind the commands, but with differences in the syntax.
Finally, the 2950's match the 2960's almost exactly, at least for the use for CCNA exam preparation. But why not get a 2960? Well, EBay buy it now at $750 (cheapest today), versus $200 for 2950. When I was writing the most recent edition of the exam cert guides, I compared the two switch models a lot - and the only difference I found that could possibly matter for CCNA was that the 2960 defaults to "switchport mode dynamic auto", whereas 2950's default to "dynamic desirable" - meaning that two 2960's won't automatically trunk by default when connected, whereas 2950's would. Nit picky, and no big deal in regards to choosing a switch for CCNA lab preparation.
OK, quick summary table on all that:

Of the items missing in the Standard image, the only one I think matters for CCNA study is the lack of RSTP (aka 802.1w).
To build a useful lab for CCNA study, I think the following are the primary criteria, in order:
  • 1. At least 2 switches, preferably 3 - allows STP and Etherchannel practice
  • 2. The ability to trunk between the switches - allows VTP and trunking practice
  • 3. The ability to use realistic commands/syntax - generally better chance of making sense of the output seen on the exams

$200:   2 x 2900XL
$300:   1 x 2900XL, 1 x 2950C
2 switches to try experiments with STP.
Additionally, on the $200 budget, I'd rather see you with 2 2900XLs, rather than a single 2950C. The benefit of having two switches to experiment with STP and VTP outweighs the benefit of having the most similar IOS (commands and syntax) compared to the 2960's, at least among the three model series that I've chosen.
Finally, for $300, I think the 2950 (standard image) is well worth it, plus a 2900XL. You can do trunking between these two switches. However, because the 1900's only support ISL, and the 2950's only support 802.1Q, at the $300 budget, I'd rather avoid 1900's altogether.


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