Securing E/0 on 1721

Unanswered Question
May 16th, 2007

I need to secure the Ethernet interface to allow ONLY my device access, as it is open to the public. How do I do this ?

I have this problem too.
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jfridlund Wed, 05/16/2007 - 10:00

No, I mean "physical" access. This router is located at a customers site and I have a device plugged into E/0. I want to secure that port from someone unplugging E/0 and using the port to try and access our network.

chris.lepa Wed, 05/16/2007 - 10:32

Hmm, the only way to address this problem (I think) is to connect a switch to that ethernet interface, then patch that connection to the switch instead of the router. On the switch, port security can be configured to only allow one static mac address.

Unless of course you mean that they have actual physical access to the router. Unauthorized personel should never have access to networking equipment and it should be locked up in an IDF or MDF.

-Chris

EDIT: Well, I guess you could use an access list to only permit your host address

(config)#access-list 101 permit host any (may not be exact syntax)

(config)#int eth0

(config-if)#ip access-group 101 in

That will just allow the host with your static IP to communicate with the network. This isn't perfiect though, because somebody else could configure another device with the same IP and have it work. The better solution would be a switch in my opinion

royalblues Wed, 05/16/2007 - 10:56

You can create an access-list and apply it on the VTY lines.

The access-list should deny the network configured on the E1/0 interface. This would prevent anyone trying to access the network.

Better way would be to just allow telnet sessions from the network management subnet

HTH, rate if it does

Narayan

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