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Port Security Overview

Juniper Networks Junos operating system (Junos OS) provides features to help secure ports on the switch. Ports can be categorized as either trusted or untrusted. You apply policies appropriate to each category to protect ports against various types of attacks.

Basic port security features are enabled in the switch's default configuration. You can configure additional features with minimal configuration steps.

Depending on the particular feature, you can configure the feature either on VLANs or interfaces.

• DHCP snooping—Filters and blocks ingress Dynamic Host Configuration Protocol (DHCP) server messages on untrusted ports; builds and maintains an IP address to MAC address binding (IP-MAC binding) database, which is called the DHCP snooping database.

  Note: DHCP snooping is not enabled in the default switch configurations. DHCP snooping is enabled on a per-VLAN basis. The details of enabling DHCP snooping depend on the particular switch.

• DHCPv6 snooping—DHCP snooping for IPv6.
• DHCP option 82—Also known as the DHCP Relay Agent information option. This DHCPv4 feature helps protect the switch against attacks such as spoofing of IP addresses and media access control (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.
• DHCPv6 option 37—Option 37 is the DHCP for IPv6 (DHCPv6) equivalent of option 82 and is enabled by default when DHCPv6 snooping is enabled on a VLAN.
• Dynamic ARP inspection (DAI)—Prevents Address Resolution Protocol (ARP) spoofing attacks. ARP requests and replies are compared against entries in the DHCP snooping database, and filtering decisions are made on the basis of the results of those comparisons. You enable DAI on a VLAN.
• IPv6 Neighbor Discovery inspection—Prevents IPv6 address spoofing attacks. Neighbor Discovery requests and replies are compared against entries in the DHCPv6 snooping database, and filtering decisions are made on the basis of the results of those comparisons. You enable Neighbor Discovery inspection on a VLAN.
• IP source guard—Mitigates the effects of IP address spoofing attacks on the Ethernet LAN. With IP source guard enabled, 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 forwarded if the source IP-MAC binding is valid; if the binding is not valid, the packet is discarded. You enable IP source guard on a VLAN. EX Series switches support IPv6 source guard also.

  Note: IP source guard is not supported on the QFX Series.

• MAC limiting—Protects against flooding of the Ethernet switching table (also known as the MAC forwarding table or Layer 2 forwarding table). You can enable MAC limiting on an interface.
• MAC move limiting—(Not supported on EX9200) Tracks MAC movement and detects MAC spoofing on access ports. You enable this feature on a VLAN.
• Persistent MAC learning—Also known as sticky MAC. Persistent MAC learning enables interfaces to retain dynamically learned MAC addresses across switch reboots You enable this feature on an interface.
• Trusted DHCP server—Configuring the DHCP server on a trusted port protects against rogue DHCP servers sending leases. You enable this feature on an interface (port). By default, access ports are untrusted, and trunk ports are trusted. (Access ports are the switch ports that connect to Ethernet endpoints such as user PCs and laptops, servers, and printers. Trunk ports are the switch ports that connect an Ethernet switch to other switches or to routers.)