Juniper M10i Hardware Manual page 37

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If there is one CFEB or CFEB-E, forwarding halts until the CFEB or CFEB-E is replaced
and functioning again. For a minimum configuration, it takes approximately 2 minutes
for the replaced CFEB or CFEB-E to boot and become active; reading in router
configuration information can take additional time, depending on the complexity of
the configuration.
If there are two CFEBs or CFEB-Es, forwarding halts while the standby CFEB or CFEB-E
boots and becomes active, which takes approximately 1 minute; synchronizing router
configuration information can take additional time, depending on the complexity of
the configuration.
For CFEB or CFEB-E replacement instructions, see "Replacing, Upgrading, or Downgrading
an M10i CFEB or CFEB-E" on page 103.
The CFEB or CFEB-E communicates with the Routing Engine using a dedicated 100-Mbps
Fast Ethernet link that transfers routing table data from the Routing Engine to the
forwarding table in the integrated ASIC. The link is also used to transfer from the CFEB
or CFEB-E to the Routing Engine routing link-state updates and other packets destined
for the router that have been received through the router interfaces.
The CFEB or CFEB-E provides the following functions:
Route lookups—Performs route lookups using the forwarding table stored in the
synchronous SRAM (SSRAM) on CFEBs or stored in the RLDRAM on CFEB-Es.
Management of shared memory —Uniformly allocates incoming data packets
throughout the router's shared memory.
Transfer of outgoing data packets—Passes data packets to the destination FIC or PIC
when the data is ready to be transmitted.
Transfer of exception and control packets—Passes exception packets to the
microprocessor on the CFEB or CFEB-E, which processes almost all of them. The
remainder are sent to the Routing Engine for further processing. Any errors originating
in the Packet Forwarding Engine and detected by the CFEB or CFEB-E are sent to the
Routing Engine using system log messages.
Chapter 2: M10i Hardware Components
11