Chassis Cluster Fabric Interfaces

Supported Fabric Interface Types for SRX Series Firewalls

For SRX Series chassis clusters, the fabric link can be any pair of Ethernet interfaces spanning the cluster; the fabric link can be any pair of Gigabit Ethernet interface.

For details about port and interface usage for management, control, and fabric links, see Understanding SRX Series Chassis Cluster Slot Numbering and Physical Port and Logical Interface Naming.

Jumbo Frame Support

The fabric data link does not support fragmentation. To accommodate this state, jumbo frame support is enabled by default on the link with an maximum transmission unit (MTU) size of 9014 bytes (9000 bytes of payload + 14 bytes for the Ethernet header) on SRX Series Firewalls. To ensure the traffic that transits the data link does not exceed this size, we recommend that no other interfaces exceed the fabric data link's MTU size.

Understanding Fabric Interfaces on SRX5000 Line of Firewalls for IOC2 and IOC3

The SRX5K-MPC (IOC2) is a Modular Port Concentrator (MPC) that is supported on the SRX5400, SRX5600, and SRX5800. This interface card accepts Modular Interface Cards (MICs), which add Ethernet ports to your services gateway to provide the physical connections to various network media types. The MPCs and MICs support fabric links for chassis clusters. The SRX5K-MPC provides 10-Gigabit Ethernet (with 10x10GE MIC), 40-Gigabit Ethernet, 100-Gigabit Ethernet, and 20x1GE Ethernet ports as fabric ports. On SRX5400 devices, only SRX5K-MPCs (IOC2) are supported.

The SRX5K-MPC3-100G10G (IOC3) and the SRX5K-MPC3-40G10G (IOC3) are Modular Port Concentrators (MPCs) that are supported on the SRX5400, SRX5600, and SRX5800. These interface cards accept Modular Interface Cards (MICs), which add Ethernet ports to your services gateway to provide the physical connections to various network media types. The MPCs and MICs support fabric links for chassis clusters.

The two types of IOC3 Modular Port Concentrators (MPCs), which have different built-in MICs, are the 24x10GE + 6x40GE MPC and the 2x100GE + 4x10GE MPC.

Due to power and thermal constraints, all four PICs on the 24x10GE + 6x40GE cannot be powered on. A maximum of two PICs can be powered on at the same time.

Use the set chassis fpc <slot> pic <pic> power off command to choose the PICs you want to power on.

Understanding Session RTOs

The data plane software, which operates in active/active mode, manages flow processing and session state redundancy and processes transit traffic. All packets belonging to a particular session are processed on the same node to ensure that the same security treatment is applied to them. The system identifies the node on which a session is active and forwards its packets to that node for processing. (After a packet is processed, the Packet Forwarding Engine transmits the packet to the node on which its egress interface exists if that node is not the local one.)

To provide for session (or flow) redundancy, the data plane software synchronizes its state by sending special payload packets called runtime objects (RTOs) from one node to the other across the fabric data link. By transmitting information about a session between the nodes, RTOs ensure the consistency and stability of sessions if a failover were to occur, and thus they enable the system to continue to process traffic belonging to existing sessions. To ensure that session information is always synchronized between the two nodes, the data plane software gives RTOs transmission priority over transit traffic.

The data plane software creates RTOs for UDP and TCP sessions and tracks state changes. It also synchronizes traffic for IPv4 pass-through protocols such as Generic Routing Encapsulation (GRE) and IPsec.

RTOs for synchronizing a session include:

• Session creation RTOs on the first packet

• Session deletion and age-out RTOs

• Change-related RTOs, including:

  • TCP state changes

  • Timeout synchronization request and response messages

  • RTOs for creating and deleting temporary openings in the firewall (pinholes) and child session pinholes

Understanding Data Forwarding

For Junos OS, flow processing occurs on a single node on which the session for that flow was established and is active. This approach ensures that the same security measures are applied to all packets belonging to a session.

A chassis cluster can receive traffic on an interface on one node and send it out to an interface on the other node. (In active/active mode, the ingress interface for traffic might exist on one node and its egress interface on the other.)

This traversal is required in the following situations:

• When packets are processed on one node, but need to be forwarded out an egress interface on the other node

• When packets arrive on an interface on one node, but must be processed on the other node

  If the ingress and egress interfaces for a packet are on one node, but the packet must be processed on the other node because its session was established there, it must traverse the data link twice. This can be the case for some complex media sessions, such as voice-over-IP (VoIP) sessions.

Understanding Fabric Data Link Failure and Recovery

Intrusion Detection and Prevention (IDP) services do not support failover. For this reason, IDP services are not applied for sessions that were present prior to the failover. IDP services are applied for new sessions created on the new primary node.

The fabric data link is vital to the chassis cluster. If the link is unavailable, traffic forwarding and RTO synchronization are affected, which can result in loss of traffic and unpredictable system behavior.

To eliminate this possibility, Junos OS uses fabric monitoring to check whether the fabric link, or the two fabric links in the case of a dual fabric link configuration, are alive by periodically transmitting probes over the fabric links. If Junos OS detects fabric faults, RG1+ status of the secondary node changes to ineligible. It determines that a fabric fault has occurred if a fabric probe is not received but the fabric interface is active. To recover from this state, both the fabric links need to come back to online state and should start exchanging probes. As soon as this happens, all the FPCs on the previously ineligible node will be reset. They then come to online state and rejoin the cluster.

If you make any changes to the configuration while the secondary node is disabled, execute the commit command to synchronize the configuration after you reboot the node. If you did not make configuration changes, the configuration file remains synchronized with that of the primary node.

When both the primary and secondary nodes are healthy (that is, there are no failures) and the fabric link goes down, RG1+ redundancy group(s) on the secondary node becomes ineligible. When one of the nodes is unhealthy (that is, there is a failure), RG1+ redundancy group(s) on this node (either the primary or secondary node) becomes ineligible. When both nodes are unhealthy and the fabric link goes down, RG1+ redundancy group(s) on the secondary node becomes ineligible. When the fabric link comes up, the node on which RG1+ became ineligible performs a cold synchronization on all Services Processing Units and transitions to active standby.

• If RG0 is primary on an unhealthy node, then RG0 will fail over from an unhealthy to a healthy node. For example, if node 0 is primary for RG0+ and node 0 becomes unhealthy, then RG1+ on node 0 will transition to ineligible after 66 seconds of a fabric link failure and RG0+ fails over to node 1, which is the healthy node.

• Only RG1+ transitions to an ineligible state. RG0 continues to be in either a primary or secondary state.

Use the show chassis cluster interfaces CLI command to verify the status of the fabric link.

Purpose

Display chassis cluster data plane interface status.

Action

From the CLI, enter the show chassis cluster data-plane interfaces command:

{primary:node1}
user@host> show chassis cluster data-plane interfaces
fab0:
    Name               Status      
    ge-2/1/9           up         
    ge-2/2/5           up         
fab1:
    Name               Status      
    ge-8/1/9           up         
    ge-8/2/5           up         

Purpose

Display chassis cluster data plane statistics.

Action

From the CLI, enter the show chassis cluster data-plane statistics command:

{primary:node1}
user@host> show chassis cluster data-plane statistics

Services Synchronized:
    Service name                              RTOs sent    RTOs received
    Translation context                       0            0
    Incoming NAT                              0            0
    Resource manager                          0            0
    Session create                            0            0
    Session close                             0            0
    Session change                            0            0
    Gate create                               0            0
    Session ageout refresh requests           0            0
    Session ageout refresh replies            0            0
    IPSec VPN                                 0            0
    Firewall user authentication              0            0
    MGCP ALG                                  0            0
    H323 ALG                                  0            0
    SIP ALG                                   0            0
    SCCP ALG                                  0            0
    PPTP ALG                                  0            0
    RTSP ALG                                  0            0