Check: JUEX-L2-000120
Juniper EX Series Switches Layer 2 Switch STIG:
JUEX-L2-000120
(in versions v1 r2 through v1 r1)
Title
The Juniper EX switch must be configured to enable DHCP snooping for all user VLANs to validate DHCP messages from untrusted sources. (Cat II impact)
Discussion
In an enterprise network, devices under administrative control are trusted sources. These devices include the switches, routers, and servers in the network. Host interfaces and unknown DHCP servers are considered untrusted sources. An unknown DHCP server on the network on an untrusted interface is called a spurious DHCP server, any device (PC, Wireless Access Point) that is loaded with DHCP server enabled. The DHCP snooping feature determines whether traffic sources are trusted or untrusted. The potential exists for a spurious DHCP server to respond to DHCPDISCOVER messages before the real server has time to respond. DHCP snooping allows switches on the network to trust the interface a DHCP server is connected to and not trust the other interfaces. The DHCP snooping feature validates DHCP messages received from untrusted sources and filters out invalid messages as well as rate-limits DHCP traffic from trusted and untrusted sources. The DHCP snooping feature builds and maintains a binding database, which contains information about untrusted hosts with leased IP addresses, and it utilizes the database to validate subsequent requests from untrusted hosts. Other security features, such as IP Source Guard and Dynamic Address Resolution Protocol (ARP) Inspection (DAI), also use information stored in the DHCP snooping binding database. Hence, it is imperative that the DHCP snooping feature is enabled on all user-facing or untrusted VLANs.
Check Content
Review the switch configuration and verify that DHCP snooping is enabled on all user-facing or untrusted VLANs. DHCP snooping is enabled if dhcp-security is configured for any VLAN, and is automatically enabled whenever any other VLAN port security feature is configured (e.g., IP Source Guard or Dynamic ARP Inspection). Devices like printers, servers, and VoIP phones are under administrative control and connected to controlled access interfaces (802.1x, Static MAC Bypass, or MAC RADIUS), making them trusted sources in non-user-facing VLANs. Verify DHCP snooping on user-facing or untrusted VLANs. [edit vlans] <untrusted VLAN name> { vlan-id <VLAN ID>; forwarding-options { dhcp-security; } } If the switch does not have DHCP snooping enabled for all user-facing or untrusted VLANs to validate DHCP messages from untrusted sources, this is a finding.
Fix Text
Configure the switch to have DHCP snooping for all user-facing or untrusted VLANs to validate DHCP messages from untrusted sources. set vlans <untrusted VLAN name> vlan-id <untrusted VLAN ID> set vlans <untrusted VLAN name> forwarding-options dhcp-security
Additional Identifiers
Rule ID: SV-253959r843910_rule
Vulnerability ID: V-253959
Group Title: SRG-NET-000362-L2S-000025
Expert Comments
CCIs
| Number | Definition |
|---|---|
| CCI-002355 |
The information system enforces access control decisions based on organization-defined security attributes that do not include the identity of the user or process acting on behalf of the user. |
| CCI-002385 |
The information system protects against or limits the effects of organization-defined types of denial of service attacks by employing organization-defined security safeguards. |