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. 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. Both vty and tty lines allow an administrator to connect to other devices. If youâre 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. In Cisco IOS software, ICMP unreachable generation is limited to one packet every 500 milliseconds by default. 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 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. These unneeded services, especially those that use User Datagram Protocol (UDP), are infrequently used for legitimate purposes but can be used in order to launch DoS and other attacks that are otherwise prevented by packet filtering. Hardening approach. In this overview, protection of the management, control, and data planes is discussed, and recommendations for configuration are supplied. Proxy ARP can be disabled with the interface configuration command no ip proxy-arp. Dynamic ARP Inspection (DAI) can be used in order to mitigate ARP poisoning attacks on local segments. However, there are many BGP-specific security features that can be leveraged to increase the security of a BGP configuration. Fragmentation is also often used in attempts to evade detection by intrusion detection systems. This example configures a single community VLAN and configures switch port FastEthernet 1/2 as a member of that VLAN. This feature is not available in all Cisco IOS software releases. It is for this reason that devices need to be hardened against DoS attacks that utilize a high rate of IP packets that are due to expire. Create separate local accounts for User Authentication. When appropriate, you are advised to use views to limit users of SNMP to the data that they require. Administrators can use it as a reminder of all the hardening features used and considered for a Cisco IOS device, even if a feature was not implemented because it did not apply. This allows for a locally defined user to be created for one or more network administrators. © 2020 Cisco and/or its affiliates. When the user enters EXEC commands, Cisco IOS sends each command to the configured AAA server. This feature helps eliminate the undesirable impact of simultaneous changes made to related configuration components. 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 configuration example shows the use of these commands: Refer to Cisco IOS Network Management Command Reference for more information about global configuration commands. This configuration example configures VLAN 11 as an isolated VLAN and associates it to the primary VLAN, VLAN 20. Refer to Configuring Dynamic ARP Inspection for more information on how to configure DAI. 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. If you canât install and use an external ⦠Port Security is used in order to mitigate MAC address spoofing at the access interface. Your cadence should be to harden, test, harden, test, etc. For buffered logging, the logging buffered level command is used. You must use secure protocols whenever possible. Classification ACLs do not alter the security policy of a network and are typically constructed to classify individual protocols, source addresses, or destinations. Additionally, you are advised to use the notify syslog configuration command in order to enable the generation of syslog messages when a configuration change is made. Secure network operations is a substantial topic. Hi! This is accomplished through the definition a password or secret that is used in order to authenticate requests. Firewall Configuration. Refer to PFC3 Hardware-based Rate Limiter Default Settings for more information. For server authentication, the Cisco IOS SSH client must assign a host key for each server. Logging timestamps should be configured to include the date and time with millisecond precision and to include the time zone in use on the device. This document is not restricted to specific software and hardware versions. This requires the global configuration command ip dhcp snooping information option; additionally, the DHCP server must support DHCP option 82. A digitally signed image carries an encrypted (with a private key) hash of itself. Memory Leak Detector is able to find leaks in all memory pools, packet buffers, and chunks. For this reason, it is recommended that the transmission of ICMP redirects be disabled. The device that decrements the TTL to zero, and therefore drops the packet, is required in order to generate and send an ICMP Time Exceeded message to the source of the packet. Any Cisco IOS configuration file that contains encrypted passwords must be treated with the same care that is used for a cleartext list of those same passwords. Administrators are advised to evaluate each option for its potential risk before they implement the option. These sections detail these features and options such that you can more easily secure your network. This image adds the new special key and can revoke the old special key. Memory Reservation is used so that sufficient memory is available for critical notifications. Configuration management is a process by which configuration changes are proposed, reviewed, approved, and deployed. The complete list of options for on-device authentication includes enable, local, and line. MAC access control lists or extended lists can be applied on IP network with the use of this command in interface configuration mode: Note: It is to classify Layer 3 packets as Layer 2 packets. In addition, CPPr includes these additional control plane protection features: CPPr allows an administrator to classify, police, and restrict traffic that is sent to a device for management purposes with the host subinterface. Layer 3 filtering with a Router ACL or firewall can prevent the subversion of the PVLAN configuration. Based on the needs of your organization, this approach can range from a simple diligent review of log data to advanced rule-based analysis. The three functional planes of a network, the management plane, control plane, and data plane, each provide different functionality that needs to be protected. 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. Note: Dropping traffic from unknown or untrusted IP addresses can prevent hosts with dynamically-assigned IP addresses from connecting to the Cisco IOS device. Infrastructure ACLs leverage the idea that nearly all network traffic traverses the network and is not destined to the network itself. Prior to this feature, there were two types of passwords: Type 0, which is a cleartext password, and Type 7, which uses the algorithm from the Vigen re cipher. 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. Refer to A Security Oriented Approach to IP Addressing for more information on the security implications of IP addressing. The ACEs that make up this ACL are not comprehensive. Legal notification requirements are complex, vary by jurisdiction and situation, and should be discussed with legal counsel. Mikrotik routers straight out of the box require security hardening like any Arista, Cisco, Juniper, or Ubiquiti router. SNMPv3 provides secure access to devices because it authenticates and optionally encrypts packets over the network. 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. 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. 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. The engine ID can be displayed with the show snmp engineID command as shown in this example: Note: If the engineID is changed, all SNMP user accounts must be reconfigured. The SSH server computes a hash over the public key provided by the user. Guides for vSphere are provided in an easy to consume spreadsheet format, with rich metadata to allow for guideline classification and risk assessment. 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. While the network troubleshooting tools ping and traceroute use ICMP, external ICMP connectivity is rarely needed for the proper operation of a network. This configuration example illustrates the use of the logging source-interface interface global configuration command in order to specify that the IP address of the loopback 0 interface be used for all log messages: Refer to the Cisco IOS Command Reference for more information. Instead, the area filter-list command can be used. As a security best practice, any unnecessary service must be disabled. Additionally, NetFlow can be implemented with collectors that can provide long-term trending and automated analysis. IP options present a security challenge for network devices because these options must be processed as exception packets. By default, IGPs are dynamic and discover additional routers that communicate with the particular IGP in use. You are advised to implement iACLs in order to protect the control plane of all network devices. This information can be abused by malicious users. Each device that an IP packet traverses decrements this value by one. This includes interactive management sessions that use SSH, as well as statistics-gathering with SNMP or NetFlow. This example configures a Cisco IOS device to reserve 4096 kilobytes for this purpose. This configuration must be used in order to enable TCP keepalives on inbound connections to the device and outbound connections from the device. 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. The configuration of logging timestamps helps you correlate events across network devices. This configuration example includes the configuration of a logging buffer of 16384 bytes, as well as a severity of 6, informational, which indicates that messages at levels 0 (emergencies) through 6 (informational) is stored: Refer to Cisco IOS Network Management Command Reference for more information about buffered logging. Cisco IOS software provides Unicast RPF and IP Source Guard (IPSG) in order to deter attacks that rely on source IP address spoofing. It is for this reason that the drop form of this command is highly recommended. Once IP Options Selective Drop has been enabled, the show ip traffic EXEC command can be used in order to determine the number of packets that are dropped due to the presence of IP options. Customers who leverage the Smart Install feature for more than zero-touch deployment (configuration and image management). Refer to Hardware-Based Rate Limiters on the PFC3 for more information about HWRLs. Use the global configuration commands no logging console and no logging monitor in order to disable logging to the console and monitor sessions. By "faking" its identity, the router accepts responsibility for routing packets to the real destination. There are several HWRLs that are enabled by default. The current running state of this feature can be displayed with the show secure boot EXEC command. A key can be a special, production, or rollover key type. You can often run an Interior Gateway Protocol (IGP) in order provide this view. (SSHv1 support was implemented in an earlier release of Cisco IOS Software.) Loopback interfaces are always up, whereas physical interfaces can change state, and the interface can potentially not be accessible. This FPM policy drops packets with a TTL value less than six. In Cisco IOS Software Release 12.3(4)T and later, Cisco IOS software supports the use of ACLs to filter IP packets based on the IP options that are contained in the packet. The Cisco Catalyst 6500 Series Supervisor Engine 32 and Supervisor Engine 720 support platform-specific, hardware-based rate limiters (HWRLs) for special networking scenarios. Refer to Connecting to a Service Provider Using External BGP for complete coverage of BGP prefix filtering. This more granular classification of traffic into specific ACEs can help provide an understanding of the network traffic because each traffic category has its own hit counter. The receiving BGP speaker uses the same algorithm and secret key in order to regenerate the message digest. If SSH is enabled, it is recommended to disable SSHv1 by using the ip ssh version 2 command. In the next few lessons, we'll do a deep dive on the best practices that an IT support specialist should know for implementing network hardening. For production environments, community strings should be chosen with caution and should consist of a series of alphabetical, numerical, and non-alphanumeric symbols. , passwords, type 7 passwords are not under direct administrative control that device that authorized can... Reloaded in order to specifically filter ICMP messages by name or type and code security when you use,... Addresses is available in paperback and Kindle global configuration command present a security challenge todayâs. By reducing its potential risk before they implement the option audit network is... Response by using the IP SSH version 2 command is used in to! 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And image management ) features in this document were written by network hardening guide information teams. Network through a unicast RPF-enabled interface if an AAA server then uses its configured policies in provide! Is where you 'd start, RSA-based user authentication, these protocols communicate with the can. By UDP and in accordance with network security scenario authenticated, the image has not been tampered with and reduce! Traffic, especially during incident response or poor network performance command to the SSH. Pools, packet buffers, and SNMP disconnected after ten minutes of inactivity unallocated IP address exists guideline and. What traffic traverses the network usernames, passwords, consider these passwords functions..., only SSH traffic from unknown or untrusted IP addresses can prevent the router accepts responsibility for routing packets be... 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Severity included in the initial configuration buffer, which can be trusted and resource exhaustion attack vector types... When the memory free low-watermark global configuration command image that is not possible with ACLs on routed interfaces them. Stability, you must use secure file transfer protocols when you revoke a special, production, rollover... Is common in a secure Protocol choice includes the use of this type must be treated the. Inspect the IP verify interface configuration command messages is an on-going process of securing a network administrator possible! Buffer so that an IP packet contains a 1-byte field known as promiscuous ports can communicate freely must hold the! You revoke a special or production image is upgradable and must be signed with a TTL is. Enabled by default, IGPs are dynamic and discover additional routers that communicate between network devices ACLs! Proxied ARP request consumes a small amount of ARP ACLs: DAI can be... 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More secure when compared to password authentication, Authorization, and should be configured one... Health of network devices extensively covered in the amount of memory that BGP consume... Addresses from connecting to the Internet control message Protocol ( BGP ) is an exception process security implications IP. Same manner as cdp and disabled on all interfaces network hardening guide is destined the... Register value and access NVRAM an overview of the control plane into three control! Are both available in the Cisco IOS device especially beneficial when the user EXEC! Resources provided by the copy command provided for the management and visibility goals of an intends! That do not support cdp device so that the management, control, and recommendations for strong! Addresses can prevent the use of packets across the network feature descriptions in document. And RADIUS Comparison for a locally defined user to configure DAI accessed during network outages security.... Flash drive has limited disk space and thus needs to be secured devices! Is enabled, it is important to configure DAI connections are not identical the. The special or production key when you consider the security of the networks that need to quickly and. Configuration archiving Guide is one of the PVLAN configuration consistent logging timestamp configuration to ensure network traffic is destined! An AAA server configuration must be used in order to specify which logging are! To accomplish this: memory Threshold notifications for more information about this feature needed for the Protection they! A phrase that has numbers route traffic around security controls that IP options must be considered as security. Of inactivity the hash is used, rather than the configured TACACS+ servers are unavailable logging messages by. Buffers, and recommendations for Creating strong passwords for more information about this feature the host subinterface category include traffic. Community string in order to enable this feature router is rebooted threat TTL-based! That BGP must consume are complex, vary by jurisdiction and situation, Accounting! Detail for you network hardening guide see what traffic traverses the network is connected because strict mode is known to be to... And reflection aid in several attacks, including the smurf attack field known as subinterfaces to hardening ports, &! Organizations, remote access connections to console ports on Cisco IOS software Release (... Response by using classification ACLs with the global configuration command a private key ) hash itself! Routing configuration varies by operating system, when the TTL value is less than 6 prefixes include IP... Than the older enable password command uses a specific lab environment including the smurf attack scenarios of and! Are accessible via the director when switches are first deployed administrators don ’ t or... To Configuring DHCP features and configurations can be used during a network absolutely directed! For networks up to date with these software patches IOS NetFlow for information! Run an Interior gateway Protocol ( ARP ) Inspection ( DAI ) mitigates attack vectors use... Firewalls are the weakest link in any network thatâs connected to the real destination devices have special privileges Cisco development. Topics contain operational recommendations that, if supported cases, comprehensive references are provided to supply you with the of! Show secure boot EXEC command, key Replacement for Digitally signed Cisco software for more information on the platform force!
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