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Cisco NX OS Switch RTR Security Technical Implementation Guide

Rules, Groups, and Values defined within the XCCDF Benchmark

  • The Cisco perimeter switch must be configured to restrict it from accepting outbound IP packets that contain an illegitimate address in the source address field via egress filter or by enabling Unicast Reverse Path Forwarding (uRPF).

    A compromised host in an enclave can be used by a malicious platform to launch cyberattacks on third parties. This is a common practice in "botnets", which are a collection of compromised computers...
    Rule High Severity
  • The Cisco perimeter switch must be configured to filter traffic destined to the enclave in accordance with the guidelines contained in DoD Instruction 8551.1.

    Vulnerability assessments must be reviewed by the System Administrator, and protocols must be approved by the Information Assurance (IA) staff before entering the enclave. ACLs are the first line ...
    Rule Medium Severity
  • The Cisco perimeter switch must be configured to filter egress traffic at the internal interface on an inbound direction.

    Access lists are used to separate data traffic into that which it will route (permitted packets) and that which it will not route (denied packets). Secure configuration of switches makes use of acc...
    Rule Medium Severity
  • The Cisco perimeter switch must be configured to block all packets with any IP options.

    Packets with IP options are not fast switched and henceforth must be punted to the switch processor. Hackers who initiate denial-of-service (DoS) attacks on switches commonly send large streams of ...
    Rule Medium Severity
  • The Cisco perimeter switch must be configured to have Cisco Discovery Protocol (CDP) disabled on all external interfaces.

    CDP is a Cisco proprietary neighbor discovery protocol used to advertise device capabilities, configuration information, and device identity. CDP is media-and-protocol-independent as it runs over l...
    Rule Low Severity
  • The Cisco perimeter switch must be configured to have Proxy ARP disabled on all external interfaces.

    When Proxy ARP is enabled on a switch, it allows that switch to extend the network (at Layer 2) across multiple interfaces (LAN segments). Because proxy ARP allows hosts from different LAN segments...
    Rule Medium Severity
  • The Cisco switch must be configured to only permit management traffic that ingresses and egresses the out-of-band management (OOBM) interface.

    The OOBM access switch will connect to the management interface of the managed network elements. The management interface can be a true OOBM interface or a standard interface functioning as the man...
    Rule Medium Severity
  • The Cisco BGP switch must be configured to check whether a single-hop eBGP peer is directly connected.

    As described in RFC 3682, GTSM is designed to protect a switch's IP-based control plane from DoS attacks. Many attacks focused on CPU load and line-card overload can be prevented by implementing GT...
    Rule Low Severity
  • The Cisco BGP switch must be configured to use a unique key for each autonomous system (AS) that it peers with.

    If the same keys are used between eBGP neighbors, the chance of a hacker compromising any of the BGP sessions increases. It is possible that a malicious user exists in one autonomous system who wou...
    Rule Medium Severity
  • The Cisco BGP switch must be configured to reject route advertisements from BGP peers that do not list their autonomous system (AS) number as the first AS in the AS_PATH attribute.

    Verifying the path a route has traversed will ensure the IP core is not used as a transit network for unauthorized or possibly even internet traffic. All autonomous system boundary switches (ASBRs)...
    Rule Low Severity
  • The Cisco BGP switch must be configured to use the maximum prefixes feature to protect against route table flooding and prefix de-aggregation attacks.

    The effects of prefix de-aggregation can degrade switch performance due to the size of routing tables and also result in black-holing legitimate traffic. Initiated by an attacker or a misconfigured...
    Rule Medium Severity
  • The Cisco BGP switch must be configured to use its loopback address as the source address for iBGP peering sessions.

    Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of the BGP switches. It is easier to construct appropriate ingress filter...
    Rule Low Severity
  • The Cisco MPLS switch must be configured to synchronize Interior Gateway Protocol (IGP) and LDP to minimize packet loss when an IGP adjacency is established prior to LDP peers completing label exchange.

    Packet loss can occur when an IGP adjacency is established and the switch begins forwarding packets using the new adjacency before the LDP label exchange completes between the peers on that link. P...
    Rule Low Severity
  • The MPLS switch with RSVP-TE enabled must be configured with message pacing to adjust maximum burst and maximum number of RSVP messages to an output queue based on the link speed and input queue size of adjacent core switches.

    RSVP-TE can be used to perform constraint-based routing when building LSP tunnels within the network core that will support QoS and traffic engineering requirements. RSVP-TE is also used to enable ...
    Rule Low Severity
  • The Cisco MPLS switch must be configured to have TTL Propagation disabled.

    The head end of the label-switched path (LSP), the label edge switch (LER) will decrement the IP packet's time-to-live (TTL) value by one and then copy the value to the MPLS TTL field. At each labe...
    Rule Medium Severity
  • The Cisco PE switch must be configured to have each Virtual Routing and Forwarding (VRF) instance with the appropriate Route Target (RT).

    The primary security model for an MPLS L3VPN as well as a VRF-lite infrastructure is traffic separation. Each interface can only be associated to one VRF, which is the fundamental framework for tra...
    Rule High Severity
  • The Cisco PE switch must be configured to have each VRF with the appropriate Route Distinguisher (RD).

    An RD provides uniqueness to the customer address spaces within the MPLS L3VPN infrastructure. The concept of the VPN-IPv4 and VPN-IPv6 address families consists of the RD prepended before the IP a...
    Rule Medium Severity
  • The Cisco PE switch providing MPLS Layer 2 Virtual Private Network (L2VPN) services must be configured to authenticate targeted Label Distribution Protocol (LDP) sessions used to exchange virtual circuit (VC) information using a FIPS-approved message authentication code algorithm.

    LDP provides the signaling required for setting up and tearing down pseudowires (virtual circuits used to transport Layer 2 frames) across an MPLS IP core network. Using a targeted LDP session, eac...
    Rule Medium Severity
  • The Cisco PE switch providing MPLS Virtual Private Wire Service (VPWS) must be configured to have the appropriate virtual circuit identification (VC ID) for each attachment circuit.

    VPWS is an L2VPN technology that provides a virtual circuit between two PE switches to forward Layer 2 frames between two customer-edge switches or switches through an MPLS-enabled IP core. The ing...
    Rule High Severity
  • The Cisco PE switch providing Virtual Private LAN Services (VPLS) must be configured to have all attachment circuits defined to the virtual forwarding instance (VFI) with the globally unique VPN ID assigned for each customer VLAN.

    VPLS defines an architecture that delivers Ethernet multipoint services over an MPLS network. Customer Layer 2 frames are forwarded across the MPLS core via pseudowires using IEEE 802.1q Ethernet b...
    Rule High Severity

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