eBGP is one such protocol. Dynamic Address Resolution Protocol (ARP) Inspection (DAI) mitigates attack vectors that use ARP poisoning on local segments. 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. Structured around the three planes into which functions of a network device can be categorized, this document provides an overview of each included feature and references to related documentation. For example, a VLAN map might be used in order to prevent hosts that are contained within the same VLAN from communication with each other, which reduces opportunities for local attackers or worms to exploit a host on the same network segment. A digitally signed image carries an encrypted (with a private key) hash of itself. The configuration of a Cisco IOS device contains many sensitive details. This is sample output from the show vstack command on a Cisco Catalyst Switch with the Smart Install client feature disabled: Disable the Smart Install client functionality after the zero-touch installation is complete or use the no vstack command. Ideally, both in-band and out-of-band management access exists for each network device so that the management plane can be accessed during network outages. In contrast, TACACS+ encrypts the entire TCP payload, which includes both the username and password. The feature Memory Threshold Notification, added in Cisco IOS Software Release 12.3(4)T, allows you to mitigate low-memory conditions on a device. If the traffic for a management session is sent over the network in cleartext, an attacker can obtain sensitive information about the device and the network. This FPM policy drops packets with a TTL value less than six. NetFlow enables you to monitor traffic flows in the network. Refer to Transit Access Control Lists: Filtering at Your Edge for more information about filtering transit and edge traffic. However, the algorithm used by the service password-encryption command is a simple Vigen re cipher. Because of the threat posed by unauthenticated FHRPs, it is recommended that instances of these protocols use MD5 authentication. ICMP redirects are disabled with the interface configuration no ip redirects command , as shown in the example configuration: IP Directed Broadcasts make it possible to send an IP broadcast packet to a remote IP subnet. This example configuration enables the use of RSA keys with SSHv2 on a Cisco IOS device: Refer to Secure Shell Version 2 Enhancements for RSA Keys for more information on the use of RSA keys with SSHv2. Administrators can use these security best practices for Cisco Smart Install deployments on affected devices: This example shows an interface ACL with the Smart Install director IP address as and the Smart Install client IP address as This ACL must be deployed on all IP interfaces on all clients. Basically, default settings of Domain Controllers are not hardened. The management plane is the plane that receives and sends traffic for operations of these functions. Implement one hardening aspect at a time and then test all server and application functionality. Since MD5 authentication is much more secure when compared to password authentication, these examples are specific to MD5 authentication. SSH provides a means to securely access and securely execute commands on another computer or device over a network. In order to deny packets from using a VLAN map, you can create an access control list (ACL) that matches the traffic and, in the VLAN map, set the action to drop. 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. Infrastructure ACLs are extensively covered in the Limit Access to the Network with Infrastructure ACLs section of this document. Computer security training, certification and free resources. These known bad prefixes include unallocated IP address space and networks that are reserved for internal or testing purposes by RFC 3330. The AAA framework provides authentication of management sessions and can also limit users to specific, administrator-defined commands and log all commands entered by all users. This traffic consists of the Receive adjacency traffic category. Fortunately, newer versions of the popular network operating systems have features that automatically check for updates and let you know when a patch should be applied. The SrcIf attribute can aid in traceback. This command verifies the integrity of image c3900-universalk9-mz.SSA in flash with the keys in the device key store: The Digitally Signed Cisco Software feature was also integrated in Cisco IOS XE Release 3.1.0.SG for the Cisco Catalyst 4500 E-Series Switches. In order to encrypt a user password with MD5 hashing, issue the username secret global configuration 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. Cisco IOS software provides functionality to specifically filter ICMP messages by name or type and code. This ensures that management processes continue to function when the memory of the device is exhausted. DAI intercepts and validates the IP-to-MAC address relationship of all ARP packets on untrusted ports. NetFlow collectors, through long-term trending, can provide network behavior and usage analysis. This CPPr policy drops transit packets received by a device where the TTL value is less than 6 and transit or non-transit packets received by a device where the TTL value is zero or one. 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. Some feature descriptions in this document were written by Cisco information development teams. TACACS+ is an authentication protocol that Cisco IOS devices can use for authentication of management users against a remote AAA server. This is possible with the use of an access control list as an option to the ip directed-broadcast command. Releases of Cisco IOS software prior to 12.0 have this functionality enabled by default. This example shows a device configuration for the Pacific Standard Time (PST) zone: Cisco IOS software includes several features that can enable a form of configuration management on a Cisco IOS device. This example illustrates the configuration of this feature: As BGP packets are received, the TTL value is checked and must be greater than or equal to 255 minus the hop-count specified. LLDP must be treated in the same manner as CDP and disabled on all interfaces that connect to untrusted networks. For example, an ACE that permits all traffic could be separated into specific protocols or ports. There are three types of Private VLANs: isolated VLANs, community VLANs, and primary VLANs. Refer to Control Plane Protection Feature Guide - 12.4T and Understanding Control Plane Protection for more information about the Cisco CPPr feature. Refer to Deploying Control Plane Policing for more information on the configuration and use of the CoPP feature. This configuration example limits log messages that are sent to remote syslog servers and the local log buffer to severities 6 (informational) through 0 (emergencies): Refer to Troubleshooting, Fault Management, and Logging for more information. By default, the Cisco IOS software sends a redirect if it receives a packet that must be routed through the interface it was received. In this situation, the router forwards the packet and sends an ICMP redirect message back to the sender of the original packet. In order to properly protect the control plane of the Cisco IOS device, it is essential to understand the types of traffic that is process switched by the CPU. 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. 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. With Cisco IOS software, it is possible to send log messages to monitor sessions - monitor sessions are interactive management sessions in which the EXEC command terminal monitor has been issued - and to the console. 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. SSHv1 is considered to be insecure and can have adverse effects on the system. If transit traffic can cause a device to process switch traffic, the control plane of a device can be affected which may lead to an operational disruption. This document describes the information to help you secure your Cisco IOS® system devices, which increases the overall security of your network. At times, you can need to quickly identify and traceback network traffic, especially during incident response or poor network performance. In order to gain knowledge about existing, emerging, and historic events related to security incidents, your organization must have a unified strategy for event logging and correlation. Passwords of this type must be eliminated and the enable secret command or the Enhanced Password Security feature needs to be used. The Authentication, Authorization, and Accounting (AAA) framework is vital to secure network devices. The first type of traffic is directed to the Cisco IOS device and must be handled directly by the Cisco IOS device CPU. 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. This example illustrates the basic configuration of this feature. Active Directory plays a critical role in the IT infrastructure, and ensures the harmony and security of different network resources in a global, interconnected environment. The log is maintained on the Cisco IOS device and contains the user information of the individual who made the change, the configuration command entered, and the time that the change was made. The Cisco Catalyst 6500 Series Supervisor Engine 32 and Supervisor Engine 720 support platform-specific, hardware-based rate limiters (HWRLs) for special networking scenarios. An authorized user who is configured with privilege level 15 cannot be locked out with this feature. The more prefixes that a router must hold, the more memory that BGP must consume. By using password authentication with routing protocols between routers, you can aid the security of the network. Note that ttys can be used for connections to console ports of other devices. The Gateway Load-Balancing Protocol (GLBP), Hot Standby Router Protocol (HSRP), and Virtual Router Redundancy Protocol (VRRP) are all FHRPs. Where possible, sufficient detail is provided for the configuration of each associated feature. In addition to the community string, an ACL should be applied that further restricts SNMP access to a select group of source IP addresses. This enables a device to generate a notification when available free memory falls lower than the specified threshold, and again when available free memory rises to five percent higher than the specified threshold. For this reason, TACACS+ should be used in preference to RADIUS when TACACS+ is supported by the AAA server. The distribute-list command is available for OSPF, but it does not prevent a router from propagating filtered routes. Refer to Secure ROMMON Configuration Example for more information about this feature. Establish, implement, and actively manage (track, report on, correct) the security configuration of network infrastructure devices using a rigorous configuration management and change control process in order to prevent attackers from exploiting vulnerable services and settings. Anyone with privileged access to a device has the capability for full administrative control of that device. TACACS+ authentication can be enabled on a Cisco IOS device with a configuration similar to this example: The previous configuration can be used as a starting point for an organization-specific AAA authentication template. As a security best practice, passwords must be managed with a TACACS+ or RADIUS authentication server. The exec-timeout command must be used in order to logout sessions on vty or tty lines that are left idle. The management plane consists of functions that achieve the management goals of the network. Command accounting is not supported with RADIUS. 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. 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. EIGRP and RIPv2 utilize Key Chains as part of the configuration. Regulations such as HIPAA, HITRUST, CMMC, and many others rely on those recommendations, demanding organizations to enforce and comply with the guide. Spoofed packets could enter the network through a Unicast RPF-enabled interface if an appropriate return route to the source IP address exists. In order to ensure that a device can be accessed via a local or remote management session, proper controls must be enforced on both vty and tty lines. Note that the ACL Support for Filtering IP Options feature can be used only with named, extended ACLs. Event logging provides you visibility into the operation of a Cisco IOS device and the network into which it is deployed. 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. It is for this reason that the drop form of this command is highly recommended. SSHv1 is insecure and not standardized, so it is not recommended if SSHv2 is an option. Dynamic ARP Inspection (DAI) can be used in order to mitigate ARP poisoning attacks on local segments. The SSHv2 support feature introduced in Cisco IOS Software Release 12.3(4)T allows a user to configure SSHv2. Specifically, portions of the IP and TCP headers, TCP payload, and a secret key are used in order to generate the digest. If your system has more than one network interface, bind MongoDB programs to the private or internal network interface. The next step is to configure an SNMPv3 group. 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