Can a router Lan port be used to connect to a cable modem.

[RonaldTidwell69310]

So,

I am new and learning and haven't found an exact answer to this thought. I have a Cisco 3845 Router I will be using for a home network. My goal was to connect my ISP cable modem to this router. So I am looking to get as much throughput as possible with a GE connection. I was wondering about using an EHWIC vs can I use one of the LAN Ports on the router. What would be the pros and cons to either one if both are an option. For example security differences and speed impacts. Thank you ahead of time. 

[Martin L]

well, home set up includes a cable modem (required by ISP) connected to home based router with 4-port switch with wireless who does NAT, DHCP, Firewall (Linksys). Usually such set up is enough for home use especially wireless connection.
you could replace home router with any Cisco router and set it up to do NAT and DHCP. 
You do have cable modem right? what is outgoing Ethernet speed? I am afraid most of them are 100 Mbps, not 1000. You do not need 1 Gig speed; for faster Internet connection you will need ISP service with 54 -108 MBps, not standard 24 Mbps (based on my old Comcast cable service).
What's reason for Cisco 3845 Router?  you could have it connected to Home router; it is tricky setup but it works.

ISP <>cable modem <>home router<>Cisco gear<>PCs

Regards, ML
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[RonaldTidwell69310]

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@Martin L wrote:

well, home set up includes a cable modem (required by ISP) connected to home based router with 4-port switch with wireless who does NAT, DHCP, Firewall (Linksys). Usually such set up is enough for home use especially wireless connection.
you could replace home router with any Cisco router and set it up to do NAT and DHCP. 
You do have cable modem right? what is outgoing Ethernet speed? I am afraid most of them are 100 Mbps, not 1000. You do not need 1 Gig speed; for faster Internet connection you will need ISP service with 54 -108 MBps, not standard 24 Mbps (based on my old Comcast cable service).
What's reason for Cisco 3845 Router?  you could have it connected to Home router; it is tricky setup but it works.

ISP <>cable modem <>home router<>Cisco gear<>PCs

Regards, ML
**Please Rate All Helpful Responses **

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As stated above I do have a cable modem from my ISP. They offer 200Mbps as there basic package, and goes up to 800Mbps. I guess my questions is can any port on my Cisco 3845 Router be sit to handle NAT and Firewall? If so, then why is there the option to install a EHWIC WAN? What would be the difference between that and a LAN port that already comes on the router? Is there a throughput difference between the two options? Is the EHWIC WAN more secure in some way?

[Martin L]

no, I don't think you need EHWIC WAN. just use one of fixed ports. you can use open slot for 8- or 16-port switching module if you need to connect some PCs or use Cisco L2/3 switch.
3845 Router is ISR -integrated Service router- comes with capabilities like Cisco IOS Firewall, Voice gateway, NAT, DHCP, VPN, and others. My old ISR, 2801, was used for voice labbing.

[Martin L]

3845 as Wi-Fi AP and other capabilities are listed in
https://www.cisco.com/c/dam/en/us/products/collateral/routers/3800-series-integrated-services-routers-isr/product_data_sheet0900aecd8049beb7.pdf