Controller Based WLANs

What is the purpose of denying UDP 68 traffic?

by on ‎07-01-2014 01:58 PM

Product and Software: This article applies to all Aruba controllers and ArubaOS versions.

 

The deny UDP 68 ACL (the default) prevents DHCP replies on a wireless network from wireless users from acting as a DHCP server.

 

If we deny UDP port 68, then what are we doing when we permit DHCP in the policy right after the deny UDP 68?

 

Example


ip access-list session control
user any udp 68 deny
any any svc-dhcp permit

 

The 'any any svc-dhcp permit' allows the udp 68 from a DHCP server to be sent to the client because the first statement is an 'any' instead of a 'user'.

 

If you had an 'any any udp 68' deny, then the client would never get an IP address because the traffic is blocked bidirectional.

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