How to Block Netbios

PRASAD BAIT · ‎08-05-2010

I have cisco 1800 series router and i want to block Netbios on that.

Jayakrishna Mada · ‎08-05-2010

Hi Prasad,

Do you have ip helper addess configured on the switch if yes then configure

no ip forward-protocol udp 137
no ip forward-protocol udp 138
no ip forward-protocol udp 139

if not you can configure and apply this access-list:

access-list 110 deny   tcp any any range 137 139

access-list 110 deny   udp any any eq netbios-ss

access-list 110 deny   udp any any eq netbios-dgm

Hope this helps.

JayaKrishna

PRASAD BAIT · ‎08-09-2010

Hi Jayakrishna,

thanks for your support.

But plz tell me that is there any need to configure the ip helper address or not???

Jayakrishna Mada · ‎08-09-2010

Prasad,

Here is the answer to your question:

There is no need to configure IP helper address if you dont have one. You can still use the access-list to block NETBIOS.

JayaKrishna