We have a rack with a Cisco Catalyst 3750 that is networked with other racks in the data center and uses bandwidth from the data center co-location (which is also an ISP). We had a need to install a Comcast Business Class modem in this rack and want to be able to manage this modem remotely. What I have done so far is:

[*] Plugged a cable into one of the 4 ports in the modem and plugged the other end into a switch port
[*] Changed the VLAN on this port to 172 (what our other servers are in)
[*] Changed the management IP of the modem to the .172.xxx subnet (what all of our servers are in, which we can reach) and changed it to the correct subnet mask


We are not able to reach the modem with this configuration and I am confused what I have wrong here. Thanks in advance for any suggestions!

Bump

When you are trying to access the modem what IP address are you coming from?

If you are coming from something outside of the Vlan172 then that will be your issue as the modem's default route will be out its internet interface not it's LAN.

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David
CCIE R&S #38338, CCIP, CCNP

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