connect new cable modem to Catalyst 2950

By rcaville ·
Comcast tried to install a new modem on our network, but backed out when the internet was unreachable from inside my lan. They said that our switch (Catalyst 2950) must be bound to the mac address of the old modem.

Now, they sent a new smc D3 modem because our existing modem is older than their support staff. I can terminal into the switch, but I am having trouble figuring out where to go from here. How do I point the switch to the new modem? Any info would be greatly appreciated. I fear that I will brick the switch, or just kill the entire network by poking around in unfamiliar territory.

thank you,

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by NetMan1958 In reply to connect new cable modem t ...

Internet <-> Modem <-> 2950 <-> Computers
Does the diagram above accurately represent your setup? If so:
(1) replace your old modem with the new one and make sure it syncs up with Comcast.
(2) Go to a computer on the network and either reboot it or run "ipconfig /release" followed by "ipconfig /renew".
(3) After that computer renews it's DHCP lease, run "ipconfig /all" and make sure the computer was assigned an ip address, a default gateway and DNS servers.
(4) While still on that same computer, try to ping the ip address that was listed as it's default gateway
(5) If the ping in step 4 was successful try to ping an ip address on the internet(such as which is google).
(6) If the ping in step 5 was successful, try to ping google via its name
(7) If step 6 was successful you should be good to go, otherwise if any of steps 1-6 fail post back which step failed and any output/error messages you received.

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