This example configuration shows how to enable the Rising and Falling Thresholds that trigger a CPU threshold notification message: Refer to CPU Thresholding Notification for more information about this feature. Any method used in order to access the console port of a device must be secured in a manner that is equal to the security that is enforced for privileged access to a device. Dynamic Address Resolution Protocol (ARP) Inspection (DAI) mitigates attack vectors that use ARP poisoning on local segments. Once a view is created and applied to a community string with the snmp-server community community-string view global configuration commands, if you access MIB data, you are restricted to the permissions that are defined by the view. Some protocols, such as IGMP, legitimately use a TTL value of one. Subinterfaces exist for Host, Transit, and CEF-Exception traffic categories. This feature often requires coordination from peering routers; however, once enabled, it can completely defeat many TCP-based attacks against BGP. The implementation of iACLs can be made easier through the use of distinct addressing for network infrastructure devices. Protocols that leverage virtual MAC addresses such as HSRP do not function when the maximum number is set to one. Man-in-the-middle attacks enable a host on the network to spoof the MAC address of the router, which results in unsuspecting hosts sending traffic to the attacker. Cisco IOS software supports the use of a local log buffer so that an administrator can view locally generated log messages. In DHCP environments, DAI uses the data that is generated by the DHCP snooping feature. This configuration example combines the previous isolated and community VLAN examples and adds the configuration of interface FastEthernet 1/12 as a promiscuous port: When you implement PVLANs, it is important to ensure that the Layer 3 configuration in place supports the restrictions that are imposed by PVLANs and does not allow for the PVLAN configuration to be subverted. Community strings should be changed at regular intervals and in accordance with network security policies. Digitally signed Cisco software keys are identified by the type and version of the key. You can use the ACL Support for Filtering on TTL Value feature, introduced in Cisco IOS Software Release 12.4(2)T, in an extended IP access list to filter packets based on TTL value. In order to view the configured users, enter the show snmp user command as shown in this example: Refer to Configuring SNMP Support for more information about this feature. As, LAN hardening is done to secure whole organization network from attacks. System hardening is needed throughout the lifecycle of technology, from initial installation, through configuration, maintenance, and support, to end-of-life decommissioning. Added to Cisco IOS Software Release 12.3(14)T, the Exclusive Configuration Change Access feature ensures that only one administrator makes configuration changes to a Cisco IOS device at a given time. Unicast RPF provides source network verification and can reduce spoofed attacks from networks that are not under direct administrative control. If a network absolutely requires directed broadcast functionality, its use should be controlled. The MPP feature allows an administrator to designate one or more interfaces as management interfaces. IP Source Guard works to minimize spoofing for networks that are under direct administrative control by performing switch port, MAC address, and source address verification. Refer to Control Plane Protection Feature Guide - 12.4T and Understanding Control Plane Protection for more information about the Cisco CPPr feature. In contrast, TACACS+ encrypts the entire TCP payload, which includes both the username and password. A device that supports CoPP and ACL Support for Filtering IP Options, introduced in Cisco IOS Software Release 12.3(4)T, may use an access list policy to filter packets that contain IP options. The size of the logging buffer is configured with the global configuration command logging buffered size. The Management Plane Protection (MPP) feature in Cisco IOS software can be used in order to help secure SNMP because it restricts the interfaces through which SNMP traffic can terminate on the device. The ROMMON image is upgradable and must be signed with the same key as the special or production image that is loaded. SNMPv3 provides secure access to devices because it authenticates and optionally encrypts packets over the network. If these protocols are in use in the network, then the ACL Support for Filtering IP Options can be used; however, the ACL IP Options Selective Drop feature could drop this traffic and these protocols might not function properly. As such, the messages it conveys can have far-reaching ramifications to the TCP and IP protocols in general. Firewalls are the first line of defense for any network that’s connected to the Internet. You can use the show memory debug leaks EXEC command in order to detect if a memory leak exists. This is in contrast to the copy filename running-config command. This makes it possible to correlate and audit network and security events across network devices more effectively. After those holes are discovered, the operating system vendors figure out how to plug the hole and release a software patch for the security fix. In some configurations, a subset of all Internet prefixes can be stored, such as in configurations that leverage only a default route or routes for a provider’s customer networks. The enable secret command must be used, rather than the older enable password command. This section provides information about physically securing domain controllers, whether the domain controllers are physical or virtual machines, in datacenter locations, branch offices, and even remote locations with only basic infrastructure controls. IP Source Guard can be applied to Layer 2 interfaces belonging to DHCP snooping-enabled VLANs. Configured prefix lists limit the prefixes that are sent or received to those specifically permitted by the routing policy of a network. This provides protection against TTL expiry attacks for networks up to five hops in width. It is recommended to add a loopback interface to each device as a management interface and that it be used exclusively for the management plane. Proxy ARP presents a resource exhaustion attack vector because each proxied ARP request consumes a small amount of memory. Cisco IOS Software Release 12.3(4)T added support for the use of ACLs to filter IP packets based on the IP options that are contained in the packet. NetFlow functions by performing analysis on specific attributes within IP packets and creating flows. There are two configuration options that are relevant when configuring buffered logging: the logging buffer size and the message severities that is stored in the buffer. It is for this reason that it is important to protect the management and control planes in preference over the data plane when you secure a network device . In order to perform password recovery, an unauthenticated attacker would need to have access to the console port and the ability to interrupt power to the device or to cause the device to crash. SNMP Views are a security feature that can permit or deny access to certain SNMP MIBs. Refer to Enabling Proxy ARP for more information on this feature. This includes routing protocols such as the Border Gateway Protocol, as well as protocols like ICMP and the Resource Reservation Protocol (RSVP). CDP can be used by Network Management Systems (NMS) or during troubleshooting. VLAN access maps support IPv4 and MAC access lists; however, they do not support logging or IPv6 ACLs. If you can’t install and use an external … GTSM for BGP is enabled with the ttl-security option for the neighbor BGP router configuration command. Although the configuration archive functionality can store up to 14 backup configurations, you are advised to consider the space requirements before you use the maximum command. SNMPv3 consists of three primary configuration options: An authoritative engine ID must exist in order to use the SNMPv3 security mechanisms - authentication or authentication and encryption - to handle SNMP packets; by default, the engine ID is generated locally. This list of protocols is used by the management plane: Steps must be taken to ensure the survival of the management and control planes during security incidents. After the required connections have been permitted, all other traffic to the infrastructure is explicitly denied. Memory Threshold Notification generates a log message in order to indicate that free memory on a device has fallen lower than the configured threshold. SSH Version 1.99 allows both SSHv1 and SSHv2 connections. The rACL protects the device from harmful traffic before the traffic impacts the route processor. Anyone with privileged access to a device has the capability for full administrative control of that device. Refer to ACL Support for Filtering on TTL Value for more information about this functionality. Traffic that contains IP options must be process-switched by Cisco IOS devices, which can lead to elevated CPU load. Infrastructure ACLs (iACLs) can be deployed in order to ensure that only end hosts with trusted IP addresses can send SNMP traffic to an IOS device. LLDP must be treated in the same manner as CDP and disabled on all interfaces that connect to untrusted networks. Spoofed packets could enter the network through a Unicast RPF-enabled interface if an appropriate return route to the source IP address exists. This command configures a Cisco IOS device for SNMPv3 with an SNMP server group AUTHGROUP and enables only authentication for this group with the auth keyword: This command configures a Cisco IOS device for SNMPv3 with an SNMP server group PRIVGROUP and enables both authentication and encryption for this group with the priv keyword: This command configures an SNMPv3 user snmpv3user with an MD5 authentication password of authpassword and a 3DES encryption password of privpassword: Note that snmp-server user configuration commands are not displayed in the configuration output of the device as required by RFC 3414; therefore, the user password is not viewable from the configuration. Note: Dropping traffic from unknown or untrusted IP addresses can prevent hosts with dynamically-assigned IP addresses from connecting to the Cisco IOS device. Key replacement and revocation replaces and removes a key that is used for a Digitally Signed Cisco Software check from a platform's key storage. Firewall Configuration. Fragmentation is also often used in attempts to evade detection by intrusion detection systems. It is critical that SNMP be properly secured in order to protect the confidentiality, integrity, and availability of both the network data and the network devices through which this data transits. Hardening guide for Cisco device. As a result, the destination IP address any that is used in the example ACL entries below only refers to the physical or virtual IP addresses of the router. After the Configuration Change Notification and Logging feature has been enabled, the privileged EXEC command show archive log config all can be used in order to view the configuration log. The optional commands hidekeys and logging size entries are used in order to improve the default configuration becuase they prevent the logging of password data and increase the length of the change log. When you configure this feature with the neighbor maximum-prefix BGP router configuration command, one argument is required: the maximum number of prefixes that are accepted before a peer is shutdown. Promiscuous ports can communicate with all other ports in the primary and secondary VLANs. This algorithm has had considerable public review and is not known to be reversible. Refer to Transit Access Control Lists: Filtering at Your Edge for more information about tACLs. This is in contrast to infrastructure ACLs that seek to filter traffic that is destined to the network itself. Isolated VLANs should be used on untrusted networks like networks that support guests. If you cannot fully prevent the use of Type 7 passwords, consider these passwords obfuscated, not encrypted. Once enabled, an administrator can cause the current running configuration to be added to the archive with the archive config privileged EXEC command. This ACL example creates a policy that filters IP packets where the TTL value is less than 6. This example describes revocation of a special key. In Cisco IOS Software Release 12.3(7)T and later, the Buffer Overflow: Detection and Correction of Redzone Corruption feature can be enabled by on a device in order to detect and correct a memory block overflow and to continue operations. While similar to CoPP, CPPr has the ability to restrict or police traffic using finer granularity than CoPP. This configuration must be used in order to enable TCP keepalives on inbound connections to the device and outbound connections from the device. Unicast RPF can be configured in one of two modes: loose or strict. These sections provide an overview of the features, benefits, and potential usage scenarios of VACLs and PACLs. The use of buffered logging is highly recommended versus logging to either the console or monitor sessions. Another feature in Cisco IOS software that can be used in order to filter packets with IP options is CoPP. Use the Password Phrase Method: • Choose a phrase that has numbers. In the previous CoPP example, the ACL entries that match the unauthorized packets with the permit action result in a discard of these packets by the policy-map drop function, while packets that match the deny action are not affected by the policy-map drop function. TACACS+ authentication, or more generally AAA authentication, provides the ability to use individual user accounts for each network administrator. The configure replace filename command replaces the running configuration as opposed to the merge performed by the copy command. If the received and computed digests are not identical, the packet is discarded. Hardening Guide The hardening guide is intended to be a living document and will be updated regularly to reflect the most up-to-date cybersecurity best practices. The following sections describe the basics of hardening your network. Proxy ARP can help machines on a subnet reach remote subnets without configuring routing or a default gateway. Even though patches are a bit of a nuisance, they’re well worth the effort for the protection that they afford. The Cisco Catalyst 6500 Series Supervisor Engine 32 and Supervisor Engine 720 support platform-specific, hardware-based rate limiters (HWRLs) for special networking scenarios. This takeover would allow an attacker to perform a man-in-the-middle attack and intercept all user traffic that exits the network. Because information can be disclosed in an interactive management session, this traffic must be encrypted so that a malicious user cannot gain access to the data that is transmitted. In Cisco IOS Software Release 12.4(4)T and later, Flexible Packet Matching (FPM) allows an administrator to match on arbitrary bits of a packet. This feature also allows configuration of the number of crashinfo files to be saved. Note: An ATA flash drive has limited disk space and thus needs to be maintained to avoid overwriting stored data. For this reason, TACACS+ should be used in preference to RADIUS when TACACS+ is supported by the AAA server. If IP options have not been completely disabled via the IP Options Selective Drop feature, it is important that IP source routing is disabled. This provides an overview of the most important BGP security features. There are no specific requirements for this document. When this feature is enabled, it is not possible to alter or remove these backup files. These subsections provide an overview of the most important IGP security features. Configuration involves the creation of an IPv4, IPv6, or MAC ACL and application of it to the Layer 2 interface. Refer to the Digitally Signed Cisco Software Key Revocation and Replacement section of the Digitally Signed Cisco Software guide for more information about this feature. This configuration example demonstrates how to enable this feature. This example configuration enables the Cisco IOS SSH client to perform RSA-based server authentication. An iACL is constructed and applied in order to specify connections from hosts or networks that need to be allowed to network devices. If the server is successfully authenticated, the session establishment continues; otherwise it is terminated and displays a Server Authentication Failed message. The current password recovery procedure enables anyone with console access to access the device and its network. Current versions of Cisco IOS software have this functionality disabled by default; however, it can be enabled via the ip directed-broadcast interface configuration command. Based on the needs of your organization, this approach can range from a simple diligent review of log data to advanced rule-based analysis. An example is the use of the Secure Copy Protocol (SCP) in place of FTP or TFTP. Customers who do not use the Smart Install feature. Refer to Recommendations for Creating Strong Passwords for more information on the selection of non-trivial passwords. If you’re building a web server, for example, you’re only going to want web … This document is not restricted to specific software and hardware versions. If your system has more than one network interface, bind MongoDB programs to the private or internal network interface. NetFlow and Classification ACLs are the two primary methods to accomplish this with Cisco IOS software. Port Security can be used in order to validate MAC addresses at the access layer. However, there are instances where it may be beneficial to perform this filtering on a Cisco IOS device in the network, for example, where filtering must be performed but no firewall is present. The Internet Control Message Protocol (ICMP) is designed as an IP control protocol. In Cisco IOS Software Release 12.4(4)T and later, Control Plane Protection (CPPr) can be used in order to restrict or police control plane traffic by the CPU of a Cisco IOS device. If you’re responsible for a DoD network, these STIGs (Security Technical Implementation Guides) will help guide your network management, configuration, and monitoring strategies across access control, operating systems, applications, network devices, and even physical security. Refer to Deploying Control Plane Policing for more information on the configuration and use of the CoPP feature. This example shows how to enable the MPP in order to only allow SSH and HTTPS on the GigabitEthernet0/1 interface: Refer to Management Plane Protection for more information about MPP. Instead, the area filter-list command can be used. A new (special or production) key for a (special or production) image comes in a (production or revocation) image that is used in order to revoke the previous special or production key. Because of the threat posed by unauthenticated FHRPs, it is recommended that instances of these protocols use MD5 authentication. The created digest is then stored in TCP option Kind 19, which was created specifically for this purpose by RFC 2385 . Refer to Memory Threshold Notifications for more information about this feature. Originally designed in order to allow quick decryption of stored passwords, Type 7 passwords are not a secure form of password storage. Mikrotik routers straight out of the box require security hardening like any Arista, Cisco, Juniper, or Ubiquiti router. The feature Enhanced Password Security, introduced in Cisco IOS Software Release 12.2(8)T, allows an administrator to configure MD5 hashing of passwords for the username command. In order to prevent resource exhaustion, it is important to configure the routing protocol to limit resource consumption. IGPs also discover routes that can be used during a network link failure. Protection is provided in various layers and is often referred to as defense in depth. The AAA server then uses its configured policies in order to permit or deny the command for that particular user. It is imperative to secure management sessions in order to prevent information disclosure and unauthorized access. This ensures that the device on the remote end of the connection is still accessible and that half-open or orphaned connections are removed from the local IOS device. This ACL example creates a policy that filters IP packets that contain any IP options: This example ACL demonstrates a policy that filters IP packets with five specific IP options. If the ip ssh verson 2 command is not explicitly configured, then Cisco IOS enables SSH Version 1.99. One of the most common interfaces that is used for in-band access to a device is the logical loopback interface. This can be used in conjunction with prefix lists in order to establish a robust set of filters. This example configures a Cisco IOS device to reserve 4096 kilobytes for this purpose. However, IP network functionality exists to alter the path of packets across the network. Infrastructure ACLs leverage the idea that nearly all network traffic traverses the network and is not destined to the network itself. The filtering provided by tACLs is beneficial when it is desirable to filter traffic to a particular group of devices or traffic that transits the network. See the Logging Best Practices section of this document for more information about how to implement logging on Cisco IOS network devices. We specialize in computer/network security, digital forensics, application security and IT audit. This example illustrates the configuration of automatic configuration archiving. Once this feature is enabled, it is possible to restore a deleted configuration or Cisco IOS software image. Command accounting is not supported with RADIUS. Note: CPPr does not support IPv6 and is restricted to the IPv4 input path. If this is not feasible due to the large number of prefixes received, a prefix list should be configured to specifically block known bad prefixes. This EIGRP example filters outbound advertisements with the distribute-list command and a prefix list: This EIGRP example filters inbound updates with a prefix list: Refer to Configuring IP Routing Protocol-Independent Features for more information about how to control the advertising and processing of routing updates. For example, an ACE that permits all traffic could be separated into specific protocols or ports. The data plane, which consists of traffic that transits the network device, should be secured to ensure the operation of the management and control planes. You are advised to enable this functionality so that the configuration change history of a Cisco IOS device can be more easily understood. Hence, the user is authenticated or denied access based on the encrypted signature. The revocation image integrity is verified with a rollover key that comes prestored on the platform. User Accounts. SSHv1 is insecure and not standardized, so it is not recommended if SSHv2 is an option. The management plane consists of functions that achieve the management goals of the network. This configuration example configures VLAN 11 as an isolated VLAN and associates it to the primary VLAN, VLAN 20. Fragmentation is also often used in attempts to evade detection by intrusion detection systems. The current running state of this feature can be displayed with the show secure boot EXEC command. While similar to CoPP, CPPr has the ability to restrict traffic with finer granularity. However, if outgoing connections are allowed, then an encrypted and secure remote access method for the connection should be enforced through the use of transport output ssh. Refer to Enhanced Password Security for more information about this feature. This is demonstrated in the configuration example: Note that some protocols, for example the RSVP, make legitimate use of IP options. The operational procedures in use on the network contribute as much to security as the configuration of the underlying devices. Refer to PFC3 Hardware-based Rate Limiter Default Settings for more information. The information in this document was created from the devices in a specific lab environment. • Use the proper case for each letter, just as it appears in the phrase. But since … During configuration of the ip verify interface configuration command, the keyword any configures loose mode while the keyword rx configures strict mode. Within the context of a Cisco IOS device configuration, two additional aspects of configuration management are critical: configuration archival and security. Once a user is locked out, their account is locked until you unlock it. See the Limiting Access to the Network with Infrastructure ACLs section of this document for more information on the use of iACLs. 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