An AUX port can be disabled with these commands: Interactive management sessions in Cisco IOS software use a tty or virtual tty (vty). 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. However, MD5 authentication is still susceptible to brute force and dictionary attacks if weak passwords are chosen. Features such as IP Options, specifically the source routing option, form a security challenge in today’s networks. This example ACL, which must be used with the access control entries (ACEs) from previous examples, allows pings from trusted management stations and NMS servers and blocks all other ICMP packets: The filter process for fragmented IP packets can pose a challenge to security devices. Stored manually or automatically, the configurations in this archive can be used in order to replace the current running configuration with the configure replace filename command. This configuration builds upon previous examples that include configuration of the TACACS servers. 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 imperative to secure management sessions in order to prevent information disclosure and unauthorized access. 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 second form of this command, ip options ignore, configures the Cisco IOS device to ignore IP options that are contained in received packets. 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. Settings for infrastructure such as Domain Name System servers, Simple Network Management Protocol configuration and time synchronization are a good starting point. 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 10.10.10.1 and the Smart Install client IP address as 10.10.10.200: This ACL must be deployed on all IP interfaces on all clients. If you can’t install and use an external … 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. A packet is dropped when its TTL value reaches zero. Refer to Configuring the Cisco IOS SSH Client to Perform RSA-Based Server Authentication for more information on the use of RSA keys with SSHv2. GTSM for BGP is enabled with the ttl-security option for the neighbor BGP router configuration command. You are advised to implement iACLs in order to protect the control plane of all network devices. Management traffic is permitted to enter a device only through these management interfaces. Refer to Enabling Proxy ARP for more information on this feature. This example uses an extended named access list that illustrates the configuration of this feature: This example demonstrates the use of a VLAN map in order to deny TCP ports 139 and 445 as well as the vines-ip protocol: Refer to Configuring Network Security with ACLs for more information about the configuration of VLAN maps. The ability of a network to properly forward traffic and recover from topology changes or faults is dependent on an accurate view of the topology. You must be aware that console ports on Cisco IOS devices have special privileges. This behavior allows the sender to bypass the router and forward future packets directly to the destination (or to a router closer to the destination). You can issue the memory reserve console global configuration command in order to enable this feature. Type 9 (scrypt) should be used whenever possible: The removal of passwords of this type can be facilitated through AAA authentication and the use of the Enhanced Password Security feature, which allows secret passwords to be used with users that are locally defined via the username global configuration command. Promiscuous ports can communicate with all other ports in the primary and secondary VLANs. The size of the logging buffer is configured with the global configuration command logging buffered size. Hackers regularly find security holes in network operating systems. In order to prevent the router from sending ICMP redirects, use the no ip redirects interface configuration command. The National Security Agency publishes some amazing hardening guides, and security information. The SSHv2 Enhancements for RSA Keys feature also supports RSA-based public key authentication for the client and server. This standard was written to provide a minimum standard for the baseline of Window Server Security and to help Administrators avoid some of the common configuration flaws that could leave systems more exposed. Classification ACLs do not alter the security policy of a network and are typically constructed to classify individual protocols, source addresses, or destinations. RIPv1 does not support authentication. The use of Transit ACLs is also relevant to the hardening of the data plane. The SSHv2 support feature introduced in Cisco IOS Software Release 12.3(4)T allows a user to configure SSHv2. In Cisco IOS Software Release 12.3(7)T and later, the Configuration Replace and Configuration Rollback features allow you to archive the Cisco IOS device configuration on the device. Instead, you are advised to send logging information to the local log buffer, which can be viewed with the show logging command. 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. This feature, added in Cisco IOS Software Release 12.3(11)T, allows a device to reclaim space in order to create new crashinfo files when the device crashes. NetFlow data can be viewed and analyzed via the CLI, or the data can be exported to a commercial or freeware NetFlow collector for aggregation and analysis. This checklist is a collection of all the hardening steps that are presented in this guide. The presence of IP options within a packet might indicate an attempt to subvert security controls in the network or otherwise alter the transit characteristics of a packet. Failure to secure the exchange of routing information allows an attacker to introduce false routing information into the network. This configuration example illustrates the use of this command: ICMP redirects are used in order to inform a network device of a better path to an IP destination. An iACL is constructed and applied in order to specify connections from hosts or networks that need to be allowed to network devices. It can also be pushed via the director when switches are first deployed. The Ubiquiti EdgeRouter Hardening Guide is over 30 pages of router security commands, advice, and best practices that you can implement in your networks. The security configuration framework is designed to help simplify security configuration while still allowing enough flexibility to allow you to balance security, productivity, and user experience. Refer to Named Method Lists for Authentication for more information about the configuration of Named Method Lists. Control Plane Policing (CoPP). First Hop Redundancy Protocols (FHRPs) provide resiliency and redundancy for devices that act as default gateways. Builds upon previous examples that include configuration of the network can protect the Cisco IOS software prior to 12.0 this. Be carefully chosen to ensure network traffic traverses the network environment also be. With unauthenticated communications securely stored and only shared with trusted individuals be treated in the Cisco security Vulnerability policy name! From unknown or untrusted IP addresses can prevent hosts with dynamically-assigned IP addresses from connecting to SSH! 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