M20
From JuniperClue
| |
| FPC/PIC Slots | 4 FPC, 16 PIC |
| Agg. Bandwidth | 12.8 Gbit/s |
| FPC Types | Type-1 |
| PIC Style | P-style |
| Power Supplies | 2 (1+1 redundant) |
| Switch Board | SSB (1+1 redundant) |
| Release date | December 7, 1999 |
The M20 (Codename: Cosmo) router is a smaller recasting of the technology in the M40 router, designed to complement the M40 for deployments needing a smaller form-factor or a reduced price point. The second Juniper Router to be released, the M20 entered beta in October 1999 and was launched in December 1999, with the JunOS 3.4 release.
The EOL plan for the M20 was announced in August 2007. The last shipment of the M20 chassis will be 31st December 2007, and M20 PICs and FPCs will not be sold beyond 31st December 2008. Final end-of-support is 31st December 2012.
Innovations
The M20 was the first Juniper router to introduce redundant Switch Boards and Routing Engines. It was also the first router to ship with the RE-2.0 333MHz routing engine.
Physical
The M20 is a rack-mount unit 14" (8 RU) in height. The system can contain up to four FPCs, and each FPC can contain up to four type-1 PICs with P-style mechanicals, or a special I-style PIC which spans 4 regular PIC slots and is integrated into its own FPC.
Power
Both AC and DC power supplies are available for the M20. The system requires one power supply for operation, with a second for redundancy. When two power supplies are operating, the load is shared across both. The maximum system power draw for a fully loaded configuration is around 1200 watts. The AC supply supports input voltages in the range of 90 to 263 volts, while the DC supply supports from -72 to -35 volts.
Cooling
The M20 is cooled side to side by three fan trays: two front trays which cool the bulk of the router, and one which cools the RE in the rear. The power supplies have their own integrated fans.
Craft Interface
The M20 provides a front panel, Craft which contains alarm lights, Routing Engine, Management Ethernet ports, serial console ports, FPC status lights and FPC offline/online buttons.
Routing Engine
The M20 originally shipped with RE-2.0 (P2 333mHz, 768MB), but now ships with RE-3.0 (P3 600mHz, 2048MB).
Forwarding
The M20 utilizes same packet forwarding ASICs as the M40, though on a different Switch Board, and thus offers better than 40 million packets per second in lookup performance. The fowarding path is the same one write, N-read path in the M40, M10, and M5.
The M20 and the M40 are the only two routers ever to be shipped with the original Internet Processor ASIC.
Hot Swapping
All removable components (power supplies, routing engines, SSBs, FPC, and fans) are hot swappable. Like the M40, an entire FPC must be disabled and removed to swap a single PIC, which requires the interruption of three unrelated PICs and is considered an annoyance. This is due entirely to mechanical considerations, as the PICs themselves are capable of being hot-swapped as long as they have been previously disabled in software (no Craft offline button exists). On later models, Juniper made mechanical changes which make it easy to PIC hotswap. It is possible, although it is unsupported and potentially risky, to hotswap PICs on the M20; see M20 PIC hotswapping for more information.
