RE vs PFE

Question 1

Whats the RE?

Answer 1

Routing Engine. Equlivent of a Cisco RSP

Question 2

What is the RE responsible for?

Answer 2

Brain of the platform and is responsible for performing protocol update and system management

runs various protocols and management software processes that reside inside a protected memory environment.

It runs on x86 or PPC CPU’s

Question 3

Whats the PFE?

Answer 3

Packet Forwarding Engine.

Its responsible for doing the actual routing and switching, for doing forwarding.

Question 4

What powers the PFE?

Answer 4

PFE typically runs on the linecards. It controls the ASICS that carry out routing/switching.

Question 5

How do the RE and PFE communicate?

Answer 5

via one or more backplane links. Depending on platform;

FXP1, EM1, BCM0

Question 6

What tables are stored on the RE?

Answer 6

Routing table (RIB)
Forwarding table (FIB)
L2 Bridging table

Question 7

What tables are stored on the PFE?

Answer 7

L2 & L3 Forwarding table (FIB)

Question 8

What is GRES?

Answer 8

Graceful Routing Engine Switchover

Question 9

What is NSR?

Answer 9

Nonstop active routing

Question 10

What are the 3 tasks the RE carries out?

Answer 10

• Maintain routing and forwarding tables
• Control and monitor the chassis, SSH, GUI, etc
• Manages the PFE by populating its L2/L3 FIB, downloading ASIC microcode, and managing the daemons.

Question 11

What are the 2 tasks the PFE has?

Answer 11

• Uses the L2/L3 FIB provided by the RE to forward traffic.

Its local copy means it can do this during an RE switchover.

• It also implements additional services such as policing, stateless firewall filtering, and Class of Service.