Cisco IOS XE Router RTR Security Technical Implementation Guide
Rules, Groups, and Values defined within the XCCDF Benchmark
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The Cisco router must be configured to produce audit records containing information to establish the source of the events.
Without establishing the source of the event, it is impossible to establish, correlate, and investigate the events leading up to an outage or attack. In order to compile an accurate risk assessmen...Rule Medium Severity -
The Cisco router must be configured to disable the auxiliary port unless it is connected to a secured modem providing encryption and authentication.
The use of POTS lines to modems connecting to network devices provides clear text of authentication traffic over commercial circuits that could be captured and used to compromise the network. Addit...Rule Low Severity -
The Cisco perimeter router must be configured to only allow incoming communications from authorized sources to be routed to authorized destinations.
Unrestricted traffic may contain malicious traffic that poses a threat to an enclave or to other connected networks. Additionally, unrestricted traffic may transit a network, which uses bandwidth a...Rule Medium Severity -
The Cisco perimeter router must be configured to protect an enclave connected to an alternate gateway by using an inbound filter that only permits packets with destination addresses within the sites address space.
Enclaves with alternate gateway connections must take additional steps to ensure there is no compromise on the enclave network or NIPRNet. Without verifying the destination address of traffic comin...Rule High Severity -
The Cisco perimeter router must be configured to not redistribute static routes to an alternate gateway service provider into BGP or an Interior Gateway Protocol (IGP) peering with the NIPRNet or to other autonomous systems.
If the static routes to the alternate gateway are being redistributed into an Exterior Gateway Protocol or Interior Gateway Protocol to a NIPRNet gateway, this could make traffic on NIPRNet flow to...Rule Low Severity -
The Cisco perimeter router 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 router must be configured to have Link Layer Discovery Protocol (LLDP) disabled on all external interfaces.
LLDP is a neighbor discovery protocol used to advertise device capabilities, configuration information, and device identity. LLDP is media-and-protocol-independent as it runs over layer 2; therefor...Rule Low Severity -
The Cisco perimeter router 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 router must be configured to have Proxy ARP disabled on all external interfaces.
When Proxy ARP is enabled on a router, it allows that router 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 perimeter router must be configured to block all outbound management traffic.
For in-band management, the management network must have its own subnet in order to enforce control and access boundaries provided by Layer 3 network nodes, such as routers and firewalls. Managemen...Rule Medium Severity -
The Cisco out-of-band management (OOBM) gateway router must be configured to transport management traffic to the Network Operations Center (NOC) via dedicated circuit, MPLS/VPN service, or IPsec tunnel.
Using dedicated paths, the OOBM backbone connects the OOBM gateway routers located at the edge of the managed network and at the NOC. Dedicated links can be deployed using provisioned circuits or M...Rule Medium Severity -
The Cisco out-of-band management (OOBM) gateway router must be configured to forward only authorized management traffic to the Network Operations Center (NOC).
The OOBM network is an IP network used exclusively for the transport of OAM&P data from the network being managed to the OSS components located at the NOC. Its design provides connectivity to each ...Rule Medium Severity -
The Cisco out-of-band management (OOBM) gateway router must be configured to not redistribute routes between the management network routing domain and the managed network routing domain.
If the gateway router is not a dedicated device for the OOBM network, several safeguards must be implemented for containment of management and production traffic boundaries; otherwise, it is possib...Rule Medium Severity -
The Cisco out-of-band management (OOBM) gateway router must be configured to block any traffic destined to itself that is not sourced from the OOBM network or the Network Operations Center (NOC).
If the gateway router is not a dedicated device for the OOBM network, several safeguards must be implemented for containment of management and production traffic boundaries. It is imperative that h...Rule Medium Severity -
The Cisco router 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 router must be configured to reject inbound route advertisements for any prefixes belonging to the local autonomous system (AS).
Accepting route advertisements belonging to the local AS can result in traffic looping or being black-holed, or at a minimum, using a non-optimized path.Rule Medium Severity -
The Cisco BGP router must be configured to reject inbound route advertisements from a customer edge (CE) router for prefixes that are not allocated to that customer.
As a best practice, a service provider should only accept customer prefixes that have been assigned to that customer and any peering autonomous systems. A multi-homed customer with BGP speaking rou...Rule Medium Severity -
The Cisco BGP router must be configured to reject outbound route advertisements for any prefixes that do not belong to any customers or the local autonomous system (AS).
Advertisement of routes by an autonomous system for networks that do not belong to any of its customers pulls traffic away from the authorized network. This causes a denial of service (DoS) on the ...Rule Medium Severity -
The Cisco BGP router must be configured to reject outbound route advertisements for any prefixes belonging to the IP core.
Outbound route advertisements belonging to the core can result in traffic either looping or being black holed, or at a minimum, using a non-optimized path.Rule Medium Severity -
The Cisco BGP router 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 routers (ASBRs) ...Rule Low Severity -
The Cisco BGP router must be configured to reject route advertisements from CE routers with an originating AS in the AS_PATH attribute that does not belong to that customer.
Verifying the path a route has traversed will ensure that the local AS is not used as a transit network for unauthorized traffic. To ensure that the local AS does not carry any prefixes that do not...Rule Low Severity -
The Cisco BGP router 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 router 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 MPLS router 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 router 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 router 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 routers.
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 PE router 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 router 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 router 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 routers to forward Layer 2 frames between two customer-edge routers or switches through an MPLS-enabled IP core. The ingre...Rule High Severity -
The Cisco PE router must be configured to enforce the split-horizon rule for all pseudowires within a Virtual Private LAN Services (VPLS) bridge domain.
A virtual forwarding instance (VFI) must be created on each participating PE router for each customer VLAN using VPLS for carrier Ethernet services. The VFI specifies the VPN ID of a VPLS domain, t...Rule Low Severity -
The Cisco PE router must be configured to implement Internet Group Management Protocol (IGMP) or Multicast Listener Discovery (MLD) snooping for each Virtual Private LAN Services (VPLS) bridge domain.
IGMP snooping provides a way to constrain multicast traffic at Layer 2. By monitoring the IGMP membership reports sent by hosts within the bridge domain, the snooping application can set up Layer 2...Rule Low Severity -
The Cisco PE router must be configured to limit the number of MAC addresses it can learn for each Virtual Private LAN Services (VPLS) bridge domain.
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 Medium Severity -
The Cisco PE router must be configured with Unicast Reverse Path Forwarding (uRPF) loose mode enabled on all CE-facing interfaces.
The uRPF feature is a defense against spoofing and denial of service (DoS) attacks by verifying if the source address of any ingress packet is reachable. To mitigate attacks that rely on forged sou...Rule Medium Severity -
The Cisco PE router must be configured to enforce a Quality-of-Service (QoS) policy to provide preferred treatment for mission-critical applications.
Different applications have unique requirements and toleration levels for delay, jitter, bandwidth, packet loss, and availability. To manage the multitude of applications and services, a network re...Rule Low Severity -
The Cisco PE router must be configured to enforce a Quality-of-Service (QoS) policy to limit the effects of packet flooding denial of service (DoS) attacks.
DoS is a condition when a resource is not available for legitimate users. Packet flooding distributed denial of service (DDoS) attacks are referred to as volumetric attacks and have the objective o...Rule Medium Severity -
The Cisco multicast router must be configured to disable Protocol Independent Multicast (PIM) on all interfaces that are not required to support multicast routing.
If multicast traffic is forwarded beyond the intended boundary, it is possible that it can be intercepted by unauthorized or unintended personnel. Limiting where, within the network, a given multic...Rule Medium Severity -
The Cisco multicast Rendezvous Point (RP) must be configured to rate limit the number of Protocol Independent Multicast (PIM) Register messages.
When a new source starts transmitting in a PIM Sparse Mode network, the DR will encapsulate the multicast packets into register messages and forward them to the RP using unicast. This process can b...Rule Medium Severity -
The Cisco multicast Designated Router (DR) must be configured to limit the number of mroute states resulting from Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Host Membership Reports.
The current multicast paradigm can let any host join any multicast group at any time by sending an IGMP or MLD membership report to the DR. In a Protocol Independent Multicast (PIM) Sparse Mode net...Rule Medium Severity -
The Cisco multicast Designated Router (DR) must be configured to set the shortest-path tree (SPT) threshold to infinity to minimalize source-group (S, G) state within the multicast topology where Any Source Multicast (ASM) is deployed.
ASM can have many sources for the same groups (many-to-many). For many receivers, the path via the RP may not be ideal compared with the shortest path from the source to the receiver. By default, t...Rule Medium Severity -
The Cisco Multicast Source Discovery Protocol (MSDP) router must be configured to authenticate all received MSDP packets.
MSDP peering with customer network routers presents additional risks to the core, whether from a rogue or misconfigured MSDP-enabled router. MSDP password authentication is used to validate each se...Rule Medium Severity -
The Cisco Multicast Source Discovery Protocol (MSDP) router must be configured to filter source-active multicast advertisements to external MSDP peers to avoid global visibility of local-only multicast sources and groups.
To avoid global visibility of local information, there are a number of source-group (S, G) states in a PIM-SM domain that must not be leaked to another domain, such as multicast sources with privat...Rule Low Severity -
The Cisco perimeter router 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 BGP router must be configured to enable the Generalized TTL Security Mechanism (GTSM).
As described in RFC 3682, GTSM is designed to protect a router's IP-based control plane from denial of service (DoS) attacks. Many attacks focused on CPU load and line-card overload can be prevente...Rule Low Severity -
The Cisco router must not be configured to use IPv6 Site Local Unicast addresses.
As currently defined, site local addresses are ambiguous and can be present in multiple sites. The address itself does not contain any indication of the site to which it belongs. The use of site-lo...Rule Medium Severity -
The Cisco perimeter router must be configured to drop IPv6 packets containing a Destination Option header with invalid option type values.
These options are intended to be for the Hop-by-Hop header only. The optional and extensible natures of the IPv6 extension headers require higher scrutiny since many implementations do not always d...Rule Medium Severity -
The Cisco perimeter router must be configured drop IPv6 packets with a Routing Header type 0, 1, or 3–255.
The routing header can be used maliciously to send a packet through a path where less robust security is in place, rather than through the presumably preferred path of routing protocols. Use of the...Rule Medium Severity
Node 2
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