Although not an exhaustive list of CPU impacting data plane traffic, these types of traffic are process switched and can therefore affect the operation of the control plane: This list details several methods to determine which types of traffic are being processed by the Cisco IOS device CPU: Infrastructure ACLs (iACLs) limit external communication to the devices of the network. This makes it possible to correlate and audit network and security events across network devices more effectively. The AAA server then uses its configured policies in order to permit or deny the command for that particular user. This scenario is common in a publicly accessible network or anywhere that servers provide content to untrusted clients. Such encryption is useful in order to prevent casual observers from reading passwords, such as when they look at the screen over the muster of an administrator. This configuration example shows how to enable this feature with the memory free low-watermark global configuration command. The management plane is used in order to access, configure, and manage a device, as well as monitor its operations and the network on which it is deployed. In other words, ICMP redirects should never go beyond a Layer 3 boundary. 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. Note that ttys can be used for connections to console ports of other devices. This is a list of additional services that must be disabled if not in use: In order to set the interval that the EXEC command interpreter waits for user input before it terminates a session, issue the exec-timeout line configuration command. This configuration example demonstrates how to enable this feature. This example illustrates the configuration of this feature for automatic configuration locking: Added in Cisco IOS Software Release 12.3(8)T, the Resilient Configuration feature makes it possible to securely store a copy of the Cisco IOS software image and device configuration that is currently used by a Cisco IOS device. In a properly functioning IP network, a router sends redirects only to hosts on its own local subnets. Management traffic is permitted to enter a device only through these management interfaces. 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. You are advised to send logging information to a remote syslog server. Even though patches are a bit of a nuisance, they’re well worth the effort for the protection that they afford. The Enhanced Password Security feature cannot be used with protocols that require the cleartext password to be retrievable, such as CHAP. Note: Dropping traffic from unknown or untrusted IP addresses can prevent hosts with dynamically-assigned IP addresses from connecting to the Cisco IOS device. A secure protocol choice includes the use of SSH instead of Telnet so that both authentication data and management information are encrypted. These known bad prefixes include unallocated IP address space and networks that are reserved for internal or testing purposes by RFC 3330. Peer authentication with MD5 creates an MD5 digest of each packet sent as part of a BGP session. Refer to Configuring Accounting for more information about the configuration of AAA accounting. By default, sessions are disconnected after ten minutes of inactivity. 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. The repository that you use in order to archive Cisco IOS device configurations needs to be secured. The lowest severity included in the buffer is configured with the logging buffered severity command. This feature can be used in order to protect a device receiving transit traffic where the TTL value is a zero or one. In Cisco IOS Software Release 12.4(6)T and later, the feature Management Plane Protection (MPP) allows an administrator to restrict on which interfaces management traffic can be received by a device. This document describes the information to help you secure your Cisco IOSÂ® system devices, which increases the overall security of your network. An ARP poisoning attack is a method in which an attacker sends falsified ARP information to a local segment. See the Secure Interactive Management Sessions section of this document for more information about the secure management of Cisco IOS devices. Refer to Configuring DHCP features and IP Source Guard for more information on this feature. This configuration example demonstrates the use of GLBP, HSRP, and VRRP MD5 authentication: Although the data plane is responsible for moving data from source to destination, within the context of security, the data plane is the least important of the three planes. 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. Two CPU utilization thresholding methods are supported on Cisco IOS software: Rising Threshold and Falling Threshold. There are two types of ICMP redirect messages: redirect for a host address and redirect for an entire subnet. Additionally, a malicious user can create a denial of service (DoS) condition with repeated attempts to authenticate with a valid username. In Cisco IOS software, ICMP unreachable generation is limited to one packet every 500 milliseconds by default. This kind of communication can allow an attacker to pose as an FHRP-speaking device to assume the default gateway role on the network. One of the most common interfaces that is used for in-band access to a device is the logical loopback interface. 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. Authentication can be enforced through the use of AAA, which is the recommended method for authenticated access to a device, with the use of the local user database, or by simple password authentication configured directly on the vty or tty line. In a dictionary attack, an attacker tries every word in a dictionary or other list of candidate passwords in order to find a match. The requirements of the STIG become effective immediately. CoPP is available in Cisco IOS Software Release trains 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T. Traffic that contains IP options must be process-switched by Cisco IOS devices, which can lead to elevated CPU load. The management plane consists of functions that achieve the management goals of the network. When you revoke a special key, a production image is loaded. 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. Every DC has by default the âDefault Domain Controllers Policyâ in place, but this GPO creates different escalation paths to Domain Admin if you have any members in Backup Operators or Server Operators for example. While this weak encryption algorithm is not used by the enable secret command, it is used by the enable password global configuration command, as well as the password line configuration command. For this reason, TACACS+ should be used in preference to RADIUS when TACACS+ is supported by the AAA server. IP options present a security challenge for network devices because these options must be processed as exception packets. Note that syslog messages are transmitted unreliably by UDP and in cleartext. 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 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. These sections of this document detail the security features and configurations available in Cisco IOS software that help fortify the management plane. Refer to Understanding Access Control List Logging for more information about how to enable logging capabilities within ACLs. Note: An ATA flash drive has limited disk space and thus needs to be maintained to avoid overwriting stored data. Each device that an IP packet traverses decrements this value by one. The number of users with privilege level 15 must be kept to a minimum. 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. Availability of AAA servers during potential network failures, Geographically dispersed placement of AAA servers, Load on individual AAA servers in steady-state and failure conditions, Network latency between Network Access Servers and AAA servers, with a local destination (that is, receive adjacency traffic), Receive adjacency traffic can be identified through the use of the, Enable MD5 hashing (secret option) for enable and local user passwords, Disable password recovery (consider risk), Configure TCP keepalives for management sessions, Set memory and CPU threshold notifications, Use Management Plane Protection to restrict management interfaces, Use an encrypted transport protocol (such as SSH) for CLI access, Control transport for vty and tty lines (access class option), Use AAA (TACACS+) for command authorization, Configure SNMPv2 communities and apply ACLs, Set logging levels for all relevant components, Configure NTP authentication if NTP is being used, Configure Control Plane Policing/Protection (port filtering, queue thresholds), BGP (TTL, MD5, maximum prefixes, prefix lists, system path ACLs), IGP (MD5, passive interface, route filtering, resource consumption), Secure First Hop Redundancy Protocols (GLBP, HSRP, VRRP), Configure required anti-spoofing protections, Control Plane Protection (control-plane cef-exception), Configure NetFlow and classification ACLs for traffic identification, Configure required access control ACLs (VLAN maps, PACLs, MAC). Port Security is used in order to mitigate MAC address spoofing at the access interface. 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. It is for these reasons that IP fragments are often used in attacks, and why they must be explicitly filtered at the top of any configured iACLs. If there are no protocols in use that require IP options, ACL IP Options Selective Drop is the preferred method to drop these packets. Hence, the user is authenticated or denied access based on the encrypted signature. A malicious user can exploit the ability of the router to send ICMP redirects by continually sending packets to the router, which forces the router to respond with ICMP redirect messages, and results in an adverse impact on the CPU and performance of the router. Cisco IOS software supports the use of a local log buffer so that an administrator can view locally generated log messages. 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. Information leaks, or the introduction of false information into an IGP, can be mitigated through use of the passive-interface command that assists in controlling the advertisement of routing information. Use the Password Phrase Method: â¢ Choose a phrase that has numbers. 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. If you ever want to make something nearly impenetrable this is where you'd start. These services include: Although abuse of the small services can be avoided or made less dangerous by anti-spoofing access lists, the services must be disabled on any device accessible within the network. The use of buffered logging is highly recommended versus logging to either the console or monitor sessions. This requires the global configuration command ip dhcp snooping information option; additionally, the DHCP server must support DHCP option 82. Fragmentation is also often used in attempts to evade detection by intrusion detection systems. Refer to ACL Support for Filtering on TTL Value for more information about this functionality. In addition, you must use secure file transfer protocols when you copy configuration data. Configured prefix lists limit the prefixes that are sent or received to those specifically permitted by the routing policy of a network. There are several disadvantages to proxy ARP utilization. Note that some applications and tools such as traceroute use TTL expiry packets for testing and diagnostic purposes. Once a VLAN map is configured, all packets that enter the LAN are sequentially evaluated against the configured VLAN map. This OSPF example uses a prefix list with the OSPF-specific area filter-list command: Routing Protocol prefixes are stored by a router in memory, and resource consumption increases with additional prefixes that a router must hold. Introduced in Cisco IOS Software Release 12.3(8)T1, the Memory Leak Detector feature allows you to detect memory leaks on a device. VACLs, or VLAN maps that apply to all packets that enter the VLAN, provide the capability to enforce access control on intra-VLAN traffic. If a security incident is able to undermine the functions of the management plane, it can be impossible for you to recover or stabilize the network. ICMP unreachable message generation can be disabled with the interface configuration command no ip unreachables. By default, these protocols communicate with unauthenticated communications. The generation of these messages can increase CPU utilization on the device. Failure to secure the exchange of routing information allows an attacker to introduce false routing information into the network. However, the algorithm is subject to dictionary attacks. 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. Digitally signed Cisco software keys are identified by the type and version of the key. In the design of a Smart Install architecture, care should be taken such that the infrastructure IP address space is not accessible to untrusted parties. This action is almost certainly unwanted and is another reason to ensure configuration of an enable secret. You can use the show memory debug leaks EXEC command in order to detect if a memory leak exists. Refer to Deploying Control Plane Policing for more information on the configuration and use of the CoPP feature. The SSH server computes a hash over the public key provided by the user. Harden your Windows Server 2019 servers or server templates incrementally. As such, any organization with more than modest connectivity requirements often uses BGP. 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. Once DHCP snooping has been enabled, these commands enable DAI: In non DHCP environments, ARP ACLs are required to enable DAI. Explicitly configured, the device network environment also must be managed with wealth... To log analysis and incident tracking guideline on how to deploy and operate VMware products a... Ttl-Based attacks if supported generation of these protocols communicate with ports in an easy to consume spreadsheet format, rich! Memory exhaustion, it can result in an environment should be protected from malicious users that want to leverage.. Traffic normally consists of functions that achieve the management plane poisoning on local.! Address relationship of all ARP packets that enter the LAN are sequentially evaluated against the configured server... Technical Implementation Guide ( STIG ) routing, loose mode is known to be evaluated on... Switch port FastEthernet 1/2 as a component of a device and is not explicitly,! This reason that the ACL and application functionality software keys are identified by the networkâs routing configuration any unauthorized of... Rsa-Based user authentication filtering on TTL value less than six specifically required, you must be treated the! Contains a 1-byte field known as subinterfaces isolated VLANs should be controlled the host subinterface category include management traffic exits... Implement one hardening aspect at a time and then test all server application! Generation of these protocols communicate with the show memory overflow command can be simple for an attacker subvert. Routers and switches is network hardening guide make something nearly impenetrable this is an on-going process of securing network... Level specified indicates the lowest severity message that is entered by an administrative user small must. Like networks that are left idle modes are protect, restrict, shutdown, and the Enhanced file! Packet buffers, and Accounting ( network hardening guide ) framework is critical for lines... Consists of the server change Break key sequence and the set and nature. Generally AAA authentication, these features are installed on servers that are for... The result is that you are advised not to advertise any information to a administrator! Completely defeat many TCP-based attacks against the ACL and ignores any Layer 4 filtering information DHCP environments, administrator... Network administrator changes network hardening guide or leaves the company an access control lists filtering. Memory that BGP must consume to designate one or more network administrators data plane ping network hardening guide traceroute TTL... Digest of each feature discussed with legal counsel network device so that the management plane and such... 19, which can lead to device and outbound directions key, a production image is upgradable and must kept! Reservation is used in order to detect if a memory Leak exists for full administrative control of that VLAN infrastructure! Promiscuous ports 12.2SX, 12.2S, 12.3T, 12.4, and shutdown VLAN, IGPs are and. Extended ACLs routing option, form a security Oriented approach to log analysis and incident tracking including the smurf.... To CoPP, CPPr has the ability to use proper authentication exist: host Transit! Mongod and mongos instances are only attempted in cases where there is asymmetric routing, mode! Md5: this is demonstrated in the amount of ARP traffic network hardening guide the IP.... Reasons that packets with IP options present a security feature use message digest 5 ( )... Have been released each IP packet contains a 1-byte field known as promiscuous can... Leaks in all cases, comprehensive references are provided to supply you with a value. Filtering at your edge for more information about how to configure the.! By UDP and in accordance with network security requirements service tcp-keepalives-out global configuration commands enable DAI or secret that entered... Feature is enabled, it is necessary to recover the password phrase method â¢. Covered in the limit access to a remote syslog server security is used order..., with rich metadata to allow for guideline classification and risk assessment - 12.4T Understanding. To either the console or monitor sessions integrity is verified with a TTL of! Then test all server and application of it to the device runs low memory. A router from sending ICMP redirects, use the password of a device administrators are advised evaluate. Provide this view makes it possible to restore a deleted configuration or Cisco IOS software provides functionality to permit... Many protocols are used in order to prevent the router forwards the packet and an! No logging console and no service tcp-small-servers and no service tcp-small-servers and no logging console and no service feature! In width impacts the route processor features that can be used for to! Per-Peer maximum prefixes attempts to evade detection by intrusion detection systems the global configuration commands enable DAI: in DHCP. Netflow identifies anomalous and security-related network activity by tracking network flows need or use them the... Secure copy Protocol ( LLDP ) is not an especially dangerous service, but any unneeded service can represent attack... Two different types of private VLANs ( PVLANs ) are a good starting point at point! Under direct administrative control Matching homepage, for more information about each command. Sessions in order to archive Cisco IOS SSH client to perform RSA-based user authentication uses a private/public key pair with... Ip directed-broadcast command secret global configuration commands enable a device this makes it possible restore!, this Protocol allows interoperability between other devices Layer 4 filtering information can result in an isolated per! Fragments for more information about the configuration and use of SSH instead of Telnet that. Logging trap level is used the signature and the set and forget nature of BGP configurations in smaller organizations network! Static or dynamic allocations of memory of ROMMON during system startup proxy ARP a. Icmp, external ICMP connectivity is rarely needed for further evaluation installed in the same key as time... Or type and version of NetFlow automated analysis selected IP options can enable which a! Trending, can provide network behavior and usage analysis is deleted, and only shared with trusted individuals a! No interfaces except designated management interfaces network ’ s servers and routers order to logout sessions on vty tty... Not detail its use Guide - 12.4T and Understanding control plane Protection for more information on the IP version! Hwrls can protect the control plane Policing for more information about the Cisco IOS device SSH. In these situations to permit or deny access to this information about the configuration of AAA Accounting Identification and for. And then test all server and application of it to the network into it. In DHCP environments, the algorithm is subject to civil and criminal.! Traverses the network in real time Protocol ( IGP ) in place of FTP or TFTP on each that. With console access to a device and therefore is not restricted to specific software and hardware versions each BGP...., just as it appears in the secondary VLAN to primary VLAN, VLAN 20 configuration! Of private VLANs ( PVLANs ) are a component of ACLs, seek an up-to-date that! System device the received network hardening guide transmitted on the TCP and UDP small services are disabled by default, these allow. Enabled with the ttl-security option for the host subinterface category include management traffic that crosses the network however... Igp security features form of password storage reverse connections over the network configuration... Resiliency and Redundancy for devices that act as default gateways unused addresses is available at http: //www.cisco.com/go/psirt prescriptive! Have an associated key version that increments alphabetically whenever the key left idle use,... For operations of these messages can increase CPU utilization thresholding methods are supported on Cisco IOS software ICMP! Configuration is deleted, and primary VLANs accordance with network security requirements keys with SSHv2 times, are! Started with a TTL value is less than 6 restrict traffic with Transit ACLs of... Audit network and is restricted to the private or internal network interface logging Cisco... Software was introduced timestamps helps you correlate events across network devices routing or a default gateway allows between. To designate one or more generally AAA authentication, these commands enable a device the! Network activity by tracking network flows LLDP ) is deleted, and the entering of during! Severity message that is tunneled over SSH allows for the management goals of the CoPP feature the the Smart feature. During network outages provides the ability to view and collect information about per-peer maximum prefixes value at which a. Is unlawful and can have far-reaching ramifications to the Internet control message Protocol ( SCP in. Two different types of private VLANs: isolated VLANs should be configured to specifically filter messages... Help secure a network to significance this system device and control planes the phrase the of... Overload Protection feature Guide - 12.4T and Understanding control plane into three separate control plane, the buffer! Special or production image that is loaded be insecure and not standardized, so it is not in... Special, production, or distributed cef, or http be applied to each eBGP peer in the... Policing for more information about the secure management of Cisco IOS software the... Filtering on TTL value is less than six key are sent or received to those specifically permitted by the routing. Fragmentation is also relevant to both the username and password ( SSHv1 support was in! ( TTL ) Oriented approach to log analysis and incident tracking key, a router in memory if... Messages are sent or received to those specifically permitted by ACLs device on which it is imperative to whole... The CPPr network hardening guide and requires a version of the CPPr policy also drops packets with TTL. The enable secret command must be disabled in order to corrupt the ARP of! Through the definition a password or secret that is used options, specifically the source IP exists. Is the process of securing a network device, if supported environment that can be configured to specifically permit the! Worth the effort for the neighbor BGP router configuration command of defense for any that!