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Planning to deploy a Cisco 1841 Router

Currently the whole building is on one network. I want to segment this network. I have a Cisco 1841 Router just sitting here. Can anyone recommend the best way to do this? The building is split into 3 levels with clients on each level connecting to hubs via utp cable on each level. In turn these hubs on each level connect via fiber to a fiber switch in the server room. This fiber switch then connects to another switch which all our servers connect too. These hubs and switches are running at 100Mbs. I would want to upgrade to 1000 so to have more available bandwidth but at the same time segment the network maybe into to two different networks if possible. Help anone!!!

7 REPLIES

Re: Planning to deploy a Cisco 1841 Router

Awfully sorry but the 1841 is not really a good choice to be used as LAN-LAN router.

Nowadays, this kind of partioning is preferrably done on a layer3 switch such as the 3750. I am afraid that your 1841 will have to remain in it's seat.

Regards,

Leo

New Member

Re: Planning to deploy a Cisco 1841 Router

So you are telling me the recommended way out is to get a 3750 switch to use as a LAN-LAN router? What can I use the 1841 for?

Re: Planning to deploy a Cisco 1841 Router

You can use it to connect your Internet line or a leased line to a remote location, or something like that type of application.

Re: Planning to deploy a Cisco 1841 Router

Hello,

I do not see a valid reason not to use the 1841 router you already have. It has two built-in 10/100 Ethernet ports, which you could use to segment your network. It is also a modular router, which means you can add modules if you require additional connectivity, which makes it even superior to the 3750, and by a lot. The only thing to keep in mind is the downlink from the router to your switch, you would need to connect the switches to the 10/100 ports with straight cables.

So, why spend a lot of money on a 3750 switch with less functionality ?

Regards,

GNT

Re: Planning to deploy a Cisco 1841 Router

Of course the 1841 can be used to break up the segments but this will likely decrease the performance of the network. I know the 1841 can do "wire speed forwarding" but you still have a serialization delay, the packets cannot be forwarded before they are completely received & checksummed. Also, a router performs a new L2 encapsulation for each packet. This is where a L3switch has the edge.

For a small network (< 100 nodes) there is no need at all for segmentation. Implementing a single "flat" layer2 is the fastest solution.

When you have come to the point where network background traffic has increased to the level at which segmentation becomes advantageous you will need a performant solution in the form of a layer3 switch.

Using an 1841 will do no harm but by design it is not suited for the job.

Regards,

Leo

New Member

Re: Planning to deploy a Cisco 1841 Router

Ok guys i get all what you are saying but I think it would still be nice if you guys could give me a direct answer on who i could do the segmentation and a list of what all i would need. This would be of help to me since I need to do a report and start with this project. Thanks!

Re: Planning to deploy a Cisco 1841 Router

Whatever you like ;-). I might have missed the urgency in your request and hence took the design-approach initially.

What you need to do is basically the following:

Step one is to divde the network in two different vlans or simply cut it in two at the physical level.

Next step involves assigning ip adresses to both LAN interfaces of your router and put it with one interface in each segment / vlan.

Basically this is all there is to it. After this you may only want to do some tuning and perhaps configure dhcp.

As I do not quite know how much help you will need with this I will leave it to these general hints for now. After all it will be you who is doing the project, not us. Please post some more specific questions or the configs so that we can efficiently guide you to your goal.

Regards,

Leo

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