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Understanding FIP Snooping

Fibre Channel over Ethernet (FCoE) Initialization Protocol (FIP) snooping is a security mechanism that is designed to prevent unauthorized access and data transmission to a Fibre Channel (FC) network. It works by filtering traffic to permit only servers that have logged in to the FC network to access the network. You enable FIP snooping on FCoE VLANs when the switch is being used as an FCoE transit switch connecting FC initiators (servers) on the Ethernet network to FCoE forwarders (FCFs) at the FC storage area network (SAN) edge.

Through the FIP process, servers that have a converged network adapter (CNA) present an FCoE Node (ENode) that can log in to the FC network. The login process establishes a dedicated virtual link between the ENode and the FCF to emulate a point-to-point connection that passes transparently through the FCoE transit switch.

The FCoE transit switch applies FIP snooping firewall filters at the edge access ports associated with the FCoE VLANs on which you enable FIP snooping. FIP snooping provides security for virtual links by automatically creating firewall filters based on information gathered (snooped) about FC devices during FIP transactions.

This topic describes:

FC Network Security

In traditional pure FC networks, the FCF is a trusted entity and server ENodes connect directly to the FCF. After an ENode gains access to the network through the fabric login (FLOGI) process, the FCF enforces zoning configurations, ensures that the ENode uses valid addresses, monitors the connection, and performs other security functions to prevent unauthorized access.

FIP snooping firewall filters emulate these security functions by preventing unauthorized access to the FCF through the transit switch and by ensuring the security of the virtual link between each ENode and the FCF. FIP snooping also prevents man-in-the-middle attacks.

FIP Snooping Functions

When you enable FIP snooping, the FCoE transit switch monitors FIP logins, solicitations, and advertisements that pass through it and gathers information about the ENode address and the address of the FCF. The transit switch uses the information to construct firewall filters that permit access only to logged-in ENodes. All other traffic on the VLAN is denied.

For example, when an ENode on an FCoE VLAN performs a successful login, the FCoE transit switch snoops the FIP information, constructs a firewall filter that permits access for the ENode, and adds the filter on all transit switch access ports associated with the FCoE VLAN.

The firewall filters allow FCoE frames to pass through the transit switch only between the server ENode FCoE port and the FCF FCoE port to which the server ENode has logged in. This ensures that ENodes can only connect to the FCFs they have successfully logged in to and that only valid FCoE traffic is transmitted. FIP snooping maintains the filters by tracking FCoE sessions.

FIP Snooping Firewall Filters

The FIP snooping firewall filters deny any FCoE traffic on the VLAN except for traffic originating from ENodes that have already logged in to the FCF.

FIP snooping performs these actions and checks to ensure that FCoE traffic is valid:

  • Denies ENodes that use the FCF media access control (MAC) address as the source address.
  • Denies all traffic from the ENode other than traffic addressed to the FCF that the Enode has logged into.
  • Restricts the ENode to sending only FCoE protocol traffic on the virtual link.
  • Allows the ENode to transmit only FIP and FCoE frames to the FCF address.
  • Ensures that the FCoE source address an ENode uses after fabic login and fabric discovery (FDISC) is the address the FCF assigned to that ENode.
  • Ensures that the FCoE source address the FCF assigns or accepts is only used for FCoE traffic.
  • Ensures that FCoE frames are only addressed to the accepting FCF.

FIP Snooping Implementation

You enable FIP snooping on a per-VLAN basis. The FCoE transit switch snoops FIP frames at the access ports associated with the FIP snooping-enabled VLANs, then installs the resulting firewall filters on the access ports to ensure that all snooping occurs on the FCoE transit switch network edge.

FCoE VLANs can include both access ports and trunk ports. Access ports face the hosts (FCoE servers and other FCoE initiators), and trunk ports face the FCF. When FIP snooping is enabled, the FCoE transit switch inspects both FIP frames and FCoE frames.

The FIP snooping implementation includes these considerations:

Server ENode-Facing Interfaces

We recommend that you enable FIP snooping on all FCoE access ports to ensure secure connections to FCFs. After you enable FIP snooping on an FCoE VLAN, the transit switch denies FCoE traffic from any server on that VLAN until the server performs a valid fabric login with an FCF.

FCF-Facing Interfaces

You must configure the interface that you are using to connect to an FCF as FCoE trusted interface, and it must be a 10 Gigabit Ethernet interface.

An FCoE trusted interface receives FCoE traffic only from an FCF. The following conditions apply to FCFs and FCF-facing interfaces:

  • By default, FCFs are trusted entities.
  • The FCoE transit switch always processes FCF frames because they come from a trusted source.

FCoE Mapped Address Prefix

When you enable FIP snooping on a VLAN, optionally you can specify the FCoE Mapped Address Prefix (FC-MAP) value for that VLAN if the network uses the fabric-provided MAC address (FPMA) addressing scheme. The FC-MAP value is a 24-bit value that identifies the FCF. The FCF combines the FC-MAP value with a unique 24-bit Fibre Channel ID (FCID) value for the server during the fabric login process, creating a unique 48-bit identifier. The FCF assigns the 48-bit value to the server ENode as its MAC address and unique identifier for the session. Each server session the ENode establishes with the FCF receives a unique FCID, so a server can host multiple virtual links to an FCF, each with a unique 48-bit address identifier.

The FIP snooping filter compares the configured FC-MAP value with the FC-MAP value in the header of frames coming from the server. If the values do not match, the FCoE transit switch denies access.

T11 FIP Snooping Specification

For more details about FIP snooping, see the Technical Committee T11 organization document Increasing FCoE Robustness using FIP Snooping at http://www.t11.org/ftp/t11/pub/fc/bb-5/08-264v3.pdf.


Published: 2010-11-14