DSL question

[Trifecta]

So i am about to get DSL with the cisco 675? modem...

I purchased the Linksys router (with built in switch) is this necessary? I heard that that cisco modem is basically a firewall/router itself.

So do I just need a switch and thats it?

what about the need for a firewall?

 

[SufferinSuccotash]

Here's how your network should look:

DSL-->modem-->router-->firewall-->hub/switch-->rest o' the network

In many cases the router and the firewall are actually the same piece of equipment. If the Cisco router is also a firewall and does either IP Masquerading or Network Address Translation (NAT for short, the two are the same thing, really), then you don't need the Linksys router. Just givethe computers on the network non-routable IP's. There are four blocks (until about a week ago I thought there were only three, someone want to verify this?) of non-routable IP address:

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.16.128.255
192.168.0.0 - 192.168.255.255

If the fourth one does exist, I'm not sure what it is.

 

[Akash]

172.0.0.0 - 172.255.255.255
depending on how you subnet the ip address
but there are plenty
i think the cisco 675 dsl modem is a router but i am not sure

 

[Russ]

SufferinSuccotash essentially outlined my setup:

DSL-->Cisco 675-->Linksys 4 port router/firewall-->D-Link 8 port switch(X2)-->'puters.

I've never tried the Cisco without the router, so I don't know if it does firewalling/NAT, but I don't think it does DHCP. The router does DHCP, and makes adding and re-arranging systems a no-brainer.

Russ, NCNE

 

[Xtremist]

Here's mine:

DSL--->Cisco 675--->Linksys Hub--->All my computers

So whatever that tells you It will do NAT, although I don't think it has a firewall built-in. It serves fine as a router (from my understanding of them; very basic). My ISP gave me a range of static IP's I get to use and each of my computer's are assigned one as well as the Cisco. The Cisco's IP is the "gateway" in my TCP/IP Properties as well. In fact, I've always referred to it as a DSL router, never a "modem". The Cisco info page on it also says it's a router:

http://www.cisco.com/univercd/cc/td/doc/pcat/675.htm

Hope that answers your question?

 

[FUBAR]

Here's how you can do it for the most ease:

DSL-->Cisco 675-->switch/hub-->x number of 'puters.

No need for the linksys.

If the ISP is using DHCP on their side, then the cisco gets the 'real' IP. Most of the time, when you get the cisco, it will be configured for DHCP and NAT. If it's not, look in the documentation for the modem on DHCP server mode.

here's what will happen (or at least what did with mine on US-West)

Cisco gets 209.181.218.xx address from ISP.
Cisco takes 10.0.0.1 for eth0 and uses it for gateway to DHCP clients.
First PC plugged into the hub gets 10.0.0.2
Second gets 10.0.0.3
Everyone's happy.

In most cases it does NAT, and it is also a damn good firewall. There are no ports of any kind that point into the network by default, so there's no way to get in to your pc's. If you want you can set up port forwarding rules for web servers, ftp servers, and other things.

I tested it on that gre.net or secure-me.net or whatever they are and I showed up as a firewall.