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Understanding Access Control on Switches


Juniper Networks Junos operating system (Junos OS) is a network operating system that has been hardened through the separation of control forwarding and services planes, with each function running in protected memory. The control-plane CPU is protected by rate limiting, routing policy, and firewall filters to ensure switch uptime even under severe attack. Access port security features such as dynamic Address Resolution Protocol (ARP) inspection, DHCP snooping, and MAC limiting are controlled through a single Junos OS CLI command.

Juniper Networks EX Series Ethernet Switches provide the following hardware and software security features:

Console Port—Allows use of the console port to connect to the Routing Engine through an RJ-45 cable. You then use the command-line interface (CLI) to configure the switch.

Out-of-Band Management—A dedicated management Ethernet port on the rear panel allows out-of-band management.

Software Images—All Junos OS images are signed by Juniper Networks certificate authority (CA) with public key infrastructure (PKI).

User Authentication, Authorization, and Accounting (AAA)—Features include:

  • User and group accounts with password encryption and authentication.

  • Access privilege levels configurable for login classes and user templates.

  • RADIUS authentication, TACACS+ authentication, or both, for authenticating users who attempt to access the switch.

  • Auditing of configuration changes through system logging or RADIUS/TACACS+.

802.1X Authentication—Provides network access control. Supplicants (hosts) are authenticated when they initially connect to a LAN. Authenticating supplicants before they receive an IP address from a DHCP server prevents unauthorized supplicants from gaining access to the LAN. EX Series switches support Extensible Authentication Protocol (EAP) methods, including EAP-MD5, EAP-TLS, EAP-TTLS, and EAP-PEAP.

Port Security—Access port security features include:

  • DHCP snooping—Filters and blocks ingress DHCP server messages on untrusted ports; builds and maintains an IP-address/MAC-address binding database (called the DHCP snooping database).

  • Dynamic ARP inspection (DAI)—Prevents ARP spoofing attacks. ARP requests and replies are compared against entries in the DHCP snooping database, and filtering decisions are made based on the results of those comparisons.

  • MAC limiting—Protects against flooding of the Ethernet switching table.

  • MAC move limiting—Detects MAC movement and MAC spoofing on access ports.

  • Trusted DHCP server—With a DHCP server on a trusted port, protects against rogue DHCP servers sending leases.

  • IP source guard—Mitigates the effects of IP address spoofing attacks on the Ethernet LAN. The source IP address in the packet sent from an untrusted access interface is validated against the source MAC address in the DHCP snooping database. The packet is allowed for further processing if the source IP address to source MAC address binding is valid; if the binding is not valid, the packet is discarded.

  • DHCP option 82—Also known as the DHCP relay agent information option. Helps protect the EX Series switch against attacks such as spoofing (forging) of IP addresses and MAC addresses and DHCP IP address starvation. Option 82 provides information about the network location of a DHCP client, and the DHCP server uses this information to implement IP addresses or other parameters for the client.

  • Unrestricted proxy ARP—The switch responds to all ARP messages with its own MAC address. Hosts that are connected to the switch’s interfaces cannot communicate directly with other hosts. Instead, all communications between hosts go through the switch.

  • Restricted proxy ARP—The switch does not respond to an ARP request if the physical networks of the source and target of the ARP request are the same. It does not matter whether the destination host has the same IP address as the incoming interface or a different (remote) IP address. An ARP request for a broadcast address elicits no reply.

Device Security—Storm control permits the switch to monitor unknown unicast and broadcast traffic and drop packets, or shut down, or temporarily disable the interface when a specified traffic level is exceeded, thus preventing packets from proliferating and degrading the LAN. You can enable storm control on access interfaces or trunk interfaces.

Firewall Filters—Allow auditing of various types of security violations, including attempts to access the switch from unauthorized locations. Firewall filters can detect such attempts and create audit log entries when they occur. The filters can also restrict access by limiting traffic to source and destination MAC addresses, specific protocols, or, in combination with policers, to specified data rates to prevent denial of service (DoS) attacks.

Policers—Provide rate-limiting capability to control the amount of traffic that enters an interface, which acts to counter DoS attacks.

Encryption Standards—Supported standards include:

  • 128-, 192-, and 256-bit Advanced Encryption Standard (AES)

  • 56-bit Data Encryption Standard (DES) and 168-bit 3DES