Syn,
I read a post that claimed it to be possible to convert the 3550 SI to an EI.. Personally, I would recommend just buying an EI when you buy a 3550. You will eventually need access to the EI when you reach that part of your CCNP studies. That said, I would not do so now. You will not be to that point for quite some time and the prices will most assuredly drop by then. I would also refrain from investing in an 1841 router at the moment as well. The idea is to have access to all of the areas of study that you will need and of course to spend the least amount of money.
The 1841 is an Integrated Services Router (ISR). There are more, less expensive, options for an ISR such as the 871 or even the 851 models. Any router with an 8 in the third digit to the right... i.e. x8xx is an ISR. If you can get an 1841 for $400 then perhaps go for it but take into account that for $400 you can have a pair of maxed out 3640's and a pair of 2610XM's if you play your cards right.. and keep a close eye on eBay. That is FOUR routers as opposed to ONE!
For CCNA studies you could get away with two good routers ie. 3640's or 26xxXM's (2610XM, 2620XM, 2621XM et. al.) and one inexpensive router to act as your access server. This is just one design but I will try to elaborate on the possibilities here and allow you to reach your own decision.
The two good routers have been covered which leaves you with the inexpensive router that will act as your Frame Relay Switch. Any 2500 series router with two serial ports will suffice and generally run under $25. This is probably your best bet and definitely your least expensive. However, as your lab matures you will inevitably decide that you want more functionality as well as the ability to create more sophisticated topologies. These topologies will include more routers. You will see CCNP topologies with four or five routers and the CCIE topology that I referenced the other day in this forum has eight routers plus the FR Switch. You will need a router acting as an FR (Frame-Relay) Switch that has more than two serial interfaces. That is where your next decision will be based.
Two options present themselves.. One is a non-modular router such as the 2522 that has 8 serial interfaces (The 2520 has 4).. There are a few more like this model.. The problem is.. they are generally expensive although I have seen them go on eBay for under $150.. (Usually closer to $200). Option B is to purchase another modular router that supports the network module that you will need to accomodate this setup. For instance, you can buy a non-XM 2610 for under $50 then add either an NM-4A/S or an NM-8A/S dependant on the toplogy that you will need. There are several advantages to this design.
One, later on if you decide to VPN to this device from the internet (you never know where you will be tech-wise a year from now) you will not want to utilize the 25xx method so option B would have been the better choice. Second, if the router dies on you at least with option B you still have a good 4A/S or 8A/S card. With the 25xx you lose everything. Third, a 2610 and an NM-4A/S will be less expensive then a 2520.. normally.. That said, you can see which direction I prefer.
In regard to serial versus the CSU/DSU method.. That is up to you. I personally do both but I stick with serial for all of my FR stuff. It really doesn't matter.. DTE to DCE back to back cables (1ft) run around $3 on eBay. You can buy a roll of Cat5e and terminate your own. Again, I do both and both provide learning experiences.
These are some things that I would recommend you look at in regard to your lab..
ROUTER MODELS:
*3640, 3620
2610, 2611, 2612, 2620, 2621, 2650, 2651, 2691
SAME *26xxXM
1720, 1721
1760
*851, *871, *851W, *871W
2501, 2503
2520 - 2523
You can look at one ISR such as the 851W and allow it to provide internet connectivity to your home and actually see it in action.. Pretty nice. You would only want/need one ISR for lab. I placed an "*" beside my personal recommendations but take into account that for CCNA you could get away with a pair of 2610's and a 2501 and perform the majority of CCNA related tasks with the exception of SDM (Security Device Manager) functions.. (There is a free download on the Cisco site for both SDM as well as the SDM Sales Demo which will allow you to practice with SDM without a router. Nice!!!
Now let's talk about switches.. It will be quite some time before you reach the switching portion of the CCNP. Until then try to purchase switches that will be useful then but less expensive than the 3550. The 2950's come to mind. I own three 2950 switches (two are EI models but really only need one EI)... You can buy a 2950 for around $100 after shipping...
SWITCHES:
Any 2950 x3
So let us take a look at an awesome under $1500 lab for CCNA/CCNP!!!
2x 3640 routers with 128/32 no face plate ($230)
1x 2620XM router ($150)
3x 2950 switches ($330)
1x NM-4A/S ($70)
2x NM-1E2W ($100)
2x WIC-1T ($60)
2x Back to Back Cables 1ft ($10)
1x Skeletek C Model Rack 20U (Under $150)
Cat5e crossover and patch cables... ($10)
Total: $1110
This is just one suggestion and they actually have a similar setup on eBay right now for $1395! I actually intentionally rounded some of these items up but you will most likely spend around $100 less than what I have mentioned. You can spend a lot less than that on a rack as well. Just perform a search for "2 post rack" on eBay. (Remmeber, you will need a 4 post or that crazy looking Skeletek rack on the Dantak website if you want to buy yourself a server later and mount it as well. Just food for thought.
Since we are already on this topic I will mention a few other plausible goodies for your lab. Search for Managed switch, switched pdu, power ethernet controller.. These will find you some nice toys.. Also, you may wish to invest in a UPS. There is another post here discussing Radius options that discusses servers in depth.. Have fun!
B Haines
CCNA R&S, ETA FOI