Juniper JUNOS - NETWORK OPERATION GUIDE REV1 User Manual

JUNOS Internet Software Network Operations Guide: Hardware
606 ! Understanding Redundant SSBs
Understanding Redundant SSBs
Purpose Inspect redundant SSBs to ensure that they provide allocation of incoming data
packets throughout shared memory on the FPCs, transfer outgoing data cells to the
FPCs for packet reassembly, perform route lookups using the forwarding table,
monitor system components for failure and alarm conditions, and monitor FPC
operation and reset.
What Are Redundant
SSBs
SSBs are redundant when two SSBs are installed in the M20 router. The SSBs occupy
the two top slots of the card cage (
SSB0 and SSB1), and are installed into the
midplane from the front of the chassis (see Figure 231 on page 607). By default,
SSB0 is the master SSB and SSB1 is the backup. When the master SSB fails,
automatic failover occurs and the backup SSB becomes the master. You can control
which SSB is the master by including the ssb statement at the [edit chassis
redundancy
] hierarchy level in the configuration. For more information, see the
JUNOS System Basics Configuration Guide.
The SSB performs the following major functions:
! Shared memory management on the FPCs—The Distributed Buffer Manager
application-specific integrated circuit (ASIC) on the SSB uniformly allocates
incoming data packets throughout shared memory on the FPCs.
! Outgoing data cell transfer to the FPCs—A second Distributed Buffer Manager
ASIC on the SSB passes data cells to the FPCs for packet reassembly when the
data is ready to be transmitted.
! Route lookups—The Internet Processor ASIC on the SSB performs route
lookups using the forwarding table stored in synchronous SRAM (SSRAM). After
performing the lookup, the Internet Processor ASIC informs the midplane of
the forwarding decision, and the midplane forwards the decision to the
appropriate outgoing interface.
Verifying SSB Failure on page 613
1. Check the SSB Connection on page 614 Check the thumbscrews on the left and right sides of the SSB.
2. Perform a Swap Test on the SSB on page 614 1. Take the SSB offline.
2. Remove the SSB.
3. Replace the SSB with one that you know works.
4. Verify that the new SSB works by using the
show chassis
ssb
CLI command.
Switch SSB Mastership on page 615
request chassis ssb master switch <no-confirm>
Replacing the SSB on page 616
1. Take the SSB offline.
2. Remove the SSB.
3. Install a new SSB.
4. Verify that the new SSB works by using the
show chassis
ssb
CLI command.
Monitor Redundant SSB Tasks Command or Action

Juniper JUNOS - NETWORK OPERATION GUIDE REV1 Specifications

General

Brand	Juniper
Model	JUNOS - NETWORK OPERATION GUIDE REV1
Category	Software
Language	English