Catalyst 3560 and 3750
The 3560 and 3750 series have been released in four major variants:
- The original and V2 series (32Gbit/s stacking, 10/100 ports, 1Gbit/s uplinks)
- The 'G' series (same as original, but with 10/100/1000 ports)
- The 'E' series (Stackwise+, 10/100/1000, 10Gbit/s uplinks)
- The 'X' series (Same as 'E', but with MACsec, StackPower, redundant power and fans)
This article covers the series.
 Original and 'G' Series
|Catalyst 3k series|
Cisco Catalyst 3750 Stack
|Throughput:||38.7 Mpps (max)|
|Switch Fabric:||32Gbps Ring|
|Max Ports:||9x48 (432) + 9x2 (18) 10GE|
The Catalyst 3560 and 3750 are the original models in this series, characterised by the original Stackwise implementation.
 Common Architecture
The two switches share a common architecture, based on two alternating tokens allowing for efficient use of the internal 32gbps backplane.
Both series switches support up to 10/100/1000 access port speeds and up to 4xSFP uplinks. In addition, Layer 3 switching (routing) and PoE are available within this product set. With the exception of the limited Catalyst 500, the 3560 is Cisco's entry PoE switch.
The 3750 allows for Stackwise. This allows multiple switches to be stacked in a ring for redundancy and resilience. In this instance, one switch becomes the 'master' switch and all other switches 'slaves'. In this case, the master IOS is copied to each switch. The FIB is then generated on the master switch and copied to each of its slaved, for distributed forwarding.
As the port ASICs on the 3560 and 3750 are connected directly to the stack, an ingress frame will take the first available token and possibly have to traverse the entire stack (and all ports) before getting to its egress location. In the case of multicast, replication is done at each individual port.
Stackwise+ on the E and X series (see below) improves many of the caveats with the original implementation, while remaining backwards compatible.
 E Series
The E Series is a general improvement on the architecture of the original models.
The basic architecture of the new switches is a 128Gbps switch fabric connected in to three major areas:
- (Up to) 48 1GE ports
- 2x10GE ports
- 1x32Gbps Stackwise+ connection (see below)
The major improvement over the original series (see below) is the disconnection of the port ASICs from the Stackwise ring.
In the previous generation, traffic entering a port would have its lookups performed locally, but then sent on the first available ring. In the worst case, this would involve traversing all switches and all ports in the ring, even if the egress port was local. An additional limitation was that all switches are limited to 32Gbps, which was shared among them (reducing overall performance for each additional switch in the stack).
With the E series, the traffic is looked up and switched locally. In other words, the ring is only used if the operating is not local (or a multicast/broadcast message). Because each switch fabric is 128Gbps, fast local switching is obtained.
For non-local switching operations, the 32Gbps Stackwise ring is still used. In this case however, space partitioning is used. For example, if we have four switches in the ring (a, b, c and d) and a wishes to send to b, the ring is able to determine that bandwidth between c and d is free. Therefore, we get far better utilisation of the link. This is often quoted as 64Gbps, n x 32Gbps or 128Gbps.
In addition, Stackwise+ is backwards-compatible with the original 3750 switches. In this case, all of the above benefits are lost at the expense of backwards compatibility.
 10 GE
The 'E' Series switches by default have 2x10GE uplinks through Xenpaks. In addition to this, two adapter jackets are supplied, which allow 4xSFPs to fit in to the two slots. Importantly, these can be swapped at runtime without a reload.
The uplinks run at wire-rate with an ASIC speed of 23gbps for the pair.
 IOS Activation
Starting with the 'E' series desktop switches, IOS features will be software activated. In this case, similar to the PIX, a PAK (Product Activation Key) will be ordered and then combined with the serial number to generate a license key entitling the end-user to certain features.
Upon ordering, the correct license key will be applied and generally one will not need to upgrade from this. In the case of sparing, bulk PAKs would be ordered and then applied to the switch to allow either IP Base, IP Services or Advanced IP Services. At launch, crypto will not be activated, but offered as a separate download.
The Cisco License Manager will aid with implementing the licensing part across a campus.
 X Series
The X series is the last of the Catalyst 3750 and 3560 series, bringing gradual improvements over the 3560-E, including a price reduction and security enhancements
The X series provides dual-redundant power supplies and fan trays that are hot-swappable. Like the E-Series, these can be as large as 1100W to support PoE+ (30W).
The uplinks in the X series is also delivered as a module, allowing either 4x1Gbit/s, 2x10Gbit/s or 2x10Gbit/s + Netflow to be installed. This further reduces the cost compared to an E-Series stack.
Each port on the X series supports IEEE 802.1AE MACsec for encryption and Cisco's Security Group Tagging extensions.
The 3750X supports StackPower, allowing switches to aggregate power between them.