E120 and E320 Modules

The routers support SRP modules, SFM modules, line modules, and IOAs. You can use a line module for access or uplink. Access line modules receive traffic from low-speed circuits, and the system routes the traffic onto higher-speed uplink line modules and then to the core of the network. Line modules act as frame forwarding engines for the physical interfaces (the IOAs) via a passive midplane.

Most line modules, IOAs, SFMs, and SRP modules can be installed in either router. There are a few exceptions, however:

See the E120 and E320 Module Guide for module and chassis compatibility.

The front panel of each module contains a collection of status LEDs (light-emitting diodes). For information about how to interpret the LEDs, see Troubleshooting. For complete module specifications, see the E120 and E320 Module Guide.

SRP Module

Switch route processor (SRP) modules perform system management, routing table calculations and maintenance, forwarding table computations, statistics processing, configuration storage, and other control plane functions. The SRP module identifies which line modules are physically present in the chassis and monitors and controls vital functions on the line modules.

Each SRP module (Figure 5) is a PowerPC-based system with its own memory, nonvolatile storage (NVS), and power converter. The SRP module works with the SFM modules and contains a switch fabric slice common to both modules. See Fabric Slices for more information.

Note: Because of different physical dimensions and switch fabric capabilities, SRP modules are not interchangeable between all routers. For example, the SRP–100 used in the E320 router cannot be used in other E Series routers, and vice versa. See the E120 and E320 Module Guide for SRP module compatibility.

Figure 5: Representative SRP Module

Representative SRP Module

Module Details

An SRP module must be present for the router to boot. The routers support up to two redundant SRP modules operating in an active/standby configuration. The redundant SRP module takes control when a failover occurs. See Redundancy Features and the E120 and E320 Module Guide for more SRP module information.

Caution: Do not remove the SRP module while the system is running, unless you have properly issued the halt command. See JunosE System Basics Configuration Guide, Chapter 6, Managing Modules for information about the halt commands.

Note: You cannot use SRP modules of different capacities in the same configuration. For example, you cannot install a SRP-100 module and a SRP-320 module in the same router.

For details about installing SRP modules, see Installing Modules.

Nonvolatile Storage

Depending on the model, each SRP module has either two Type II PCMCIA nonvolatile storage (NVS) cards or two ATA flash cards (0, 1). (See Figure 5.) One card is loaded with the system's software and configuration files while the other card holds core dumps. The NVS cards in the active SRP module are designated disk0 and disk1. The NVS cards in the redundant SRP module are designated standby-disk0 and standby-disk1. The PCMCIA card is factory installed.

Caution: Before you insert or remove flash cards from a running router, we strongly recommend that you halt the SRP module or shut down the router. Failure to do this can result in file corruption in one or both cards. See Replacing an NVS Card for more information.

SFM Module

The switch fabric modules (SFMs) work with the SRP module to create a shared memory fabric for the router. Each SFM module (Figure 6) has its own memory and power converter. Like the SRP module, the SFM module contains a fabric system processor board (slice). See Fabric Slices.

Note: You must use a SRP module that corresponds with the fabric type (SFM module) that is installed. For example, you can only use a SRP–100 module with a SFM-100 module. You cannot use a SRP–100 module with a SFM-320 module.

Figure 6: SFM Module

SFM Module

Fabric Slices

The router's switch fabric is distributed across two SRP modules and three SFM modules. Each module has a fabric slice on it. For the router to operate, at least four of the five slices must be operational.

When all five modules are installed, the fabric slice of the standby SRP acts as a redundant module. For example, the router can operate with:

Note: You cannot use SFM modules of different capacities in the same configuration. For example, you cannot install a SFM-100 module and a SFM-320 module in the same router.


The SRP I/O adapter (IOA) is a single input/output adapter that interfaces with the SRP modules through the system's midplane. See Figure 2 and Figure 4 for its location.

Module Details

The SRP IOA provides standard management interfaces, including:

You can hot-swap SRP IOAs. Hot-swapping enables you to add or remove SRP IOAs without powering down the system. When you complete hot-swapping an SRP IOA, its MAC address in the subnet is automatically refreshed without rebooting the SRP or the chassis. Also, you can re-insert an SRP IOA that you had taken out previously to the same network without refreshing the MAC address of the SRP IOA.

Note: Hot-swapping an SRP IOA is unsupported during a unified in-service software upgrade (ISSU).

If you have configured RADIUS server on an SRP IOA that you want to replace, you can perform either of the following actions to prevent loss of accounting or logout information:

After you complete hot-swapping the SRP IOA, you can use the show version all command to display the state of the SRP IOA.

The SRP IOA hot-swapping is supported on the following routers:

Note: We recommend that you complete the hot-swapping of the SRP IOA within 1800 seconds because the console or Telnet session might be terminated during the hot-swap operation.

For details about installing the SRP IOA, see Installing Modules.

Line Modules

Line modules (LMs) act as frame forwarding engines for the physical interfaces (the IOAs) and process data from different types of network connections. For information about available line modules, and which SRP modules support specific line modules, see the E120 and E320 Module Guide.

Figure 7 shows a representative line module. For details about installing line modules, see Installing Modules.

Figure 7: Representative Line Module

Representative Line Module

Packet Classification

The line module supports packet classification on ingress. A classification engine on the line module matches specific fields (such as source and destination IP address, source and destination port, and protocol), the ingress IP interface, layer 2 fields, or some combination of these against user-configured filters at wire speed.

I/O Adapters

Most input/output adapters (IOA) provide the physical interconnection to the network via small form-factor pluggable transceivers (SFPs). You insert each IOA into the passive midplane in the rear of the chassis, directly behind a line module. See Figure 2 for IOA location in the router and Figure 8 for a representative IOA model. See Installing and Removing SFPs and the E120 and E320 Module Guide for information on SFPs.

For a list of hot-swappable IOAs, see Table 4.

Figure 8: Representative IOA

Representative IOA

An IOA bracket can be installed to create upper and lower IOA bays (E320 router) or left and right IOA bays (E120 router), enabling you to use two IOAs in the same slot. This architecture enables you to combine different IOA types in the same slot and to support oversubscribed configurations.

Restrictions exist concerning which IOAs can be combined in the same slot and which bay (upper or lower, left or right) they may be installed in. See IOA Slot Combinations and the E120 and E320 Module Guide for information. For details about installing IOAs, see Installing Modules.