topic Re: broadcast traffic in Network Security

broadcast traffic

WILLIAM STEGMAN — Mon, 11 Mar 2019 10:12:13 GMT

This has been a kind of nagging question I've had for a while, why would netbios port 137 traffic from another subnet be trying to cross my ASA's inside interface. 10.4.2.0/24 -> router -> p2p T1 -> router 10.4.0.0/16 -> ASA -> Internet

the following gets periodically logged on my ASA

4 May 10 2007 11:45:52 106023 10.4.2.39 10.255.255.255 Deny udp src inside:10.4.2.39/137 dst inside:10.255.255.255/137 by access-group "inside_access_in" [0x0, 0x0]

I always thought layer 3 devices blocked this sort of broadbcast traffic??

thanks,

Bill

Re: broadcast traffic

Jon Marshall — Thu, 10 May 2007 17:41:21 GMT

Hi Bill

10.255.255.255 is a directed broadcast. Have you turned these off under the router interfaces ie.

router(config)# int fa0

router(config-if)# no ip directed broacast

HTH

Jon

Re: broadcast traffic

WILLIAM STEGMAN — Thu, 10 May 2007 18:05:58 GMT

thank you Jon.