Distribution Band Switches
Switches acclimated in the administration band should action these features:
• Aggregation of admission band devices
• High Band 3 throughput—InterVLAN routing
• Robust Band 3 functionality
• Security
• Media translation
In the administration layer, uplinks from all admission band accessories are aggregated, or appear together.
Therefore, the administration band switches charge be able of processing the absolute accumulated of
traffic from all the affiliated devices. These switches should accept a anchorage body of high-speed
links to abutment the accumulating of admission band switches.
VLANs and advertisement domains assemble at the administration layer, acute routing, filtering,
and security. The switches at this band charge be able of assuming multilayer switching with
high throughput. This achievement is usually able with a avenue processor aural the
switch, but is additionally accessible application an alien router as the avenue processor. Alone assertive Catalyst
switch models can accommodate multilayer switching; be abiding to accept which ones can do this.
(Chapter 8, “Multilayer Switching,” covers this affair in greater detail.)
The Catalyst 2926G can serve as a administration band about-face for up to 24 10/100BaseT access
layer uplinks, as ability be begin in small- to mid-sized networks. MLS is performed by a
combination of imbedded NetFlow argumentation and an alien Cisco router. A Band 3 abstracts flow
between two endpoints is apparent and candy by the router, as would be expected.
However, already the antecedent anatomy of the abstracts breeze is routed, the NetFlow argumentation caches the frameforwarding
information. Subsequent frames are switched at wire acceleration rather than involving the
router.
3500 XL 48 10/100 2 1000BaseX 10 Gbps Stackable Gigabit
4000 96 10/100
36 1000BaseX
100 or 1000BaseX 24 Gbps Security, QoS
5000 396 10/100 Any 3.6 Gbps Modular, “any-to-any”
switching
Table 2-4 Catalyst Switches for the Admission Band (Continued)
Catalyst
Model
Max Port
Density Uplinks Max Backplane Other Features
Cisco Articles in the Hierarchical Design 35
NOTE Based on anchorage body and assertive functionality, abounding Catalyst switches can be acclimated in more
than one band of a campus network. For example, because the Catalyst 2926G offers alone a
fixed 24-port 10/100BaseT agreement with two Gigabit Ethernet uplinks, you ability appetite to
use it in base closets or the admission band to affix workgroups or hubs. The Gigabit Ethernet
uplinks would again be acclimated as links to administration band switches.
However, what sets these switches afar is the MLS or Band 3 switching function. As you’ve
learned, Band 3 switching is best aloof for the administration layer.
The Catalyst 2926G will be replaced by the Catalyst 2948G-L3 switch, with 48 10/100BaseT
ports and two Gigabit Ethernet uplinks. Again, this about-face would fit into the administration layer
of a small- to mid-sized campus. However, the Band 3 switching action is performed
completely aural the about-face rather than relying on an alien router for assistance. The
2948G-L3 about-face uses a address alleged Cisco Express Forwarding (CEF), which was
developed for higher-end about-face routers. Here, the switch’s RISC processor keeps a topology
map of the absolute arrangement and distributes that map to anniversary port-based ASIC. Band 3 switching
can be performed at wire acceleration in accouterments on the ASICs for IP, IPX, and IP multicast
protocols. Other protocols are Band 2 switched (bridged) at wire acceleration on the ASICs.
The Catalyst 4908G-L3 offers the aforementioned functionality as the 2948G-L3, but with eight Gigabit
Ethernet ports. Band 3 switching is additionally performed application CEF in the port-based ASICs. This
switch can be acclimated in the administration band of mid-sized networks, application the Gigabit Ethernet
ports to accumulated admission band devices.
For beyond campus networks, the Catalyst 5000/5500 and 6000/6500 families action high
densities of Fast and Gigabit Ethernet for the administration layer. A absolutely busy Catalyst
5509, for example, can abutment up to 38 Gigabit Ethernet ports or 288 10/100 Ethernet ports.
The Catalyst 5000 ancestors can accomplish MLS application either an chip Avenue About-face Module
(RSM), Avenue About-face Feature Card (RSFC), or an alien router, accompanying with the integrated
NetFlow Feature Card (NFFC).
The Catalyst 6000 ancestors offers abundant college achievement and anchorage body that can be acclimated in
large administration layers. For example, the Catalyst 6509 can abutment up to 130 Gigabit Ethernet
ports or 384 10/100 Ethernet ports. MLS can be performed application an chip Multilayer
Switch Feature Card (MSFC), accouterment a throughput of up to 150 actor packets per second.
Table 2-5 in the area “Product Summary” provides advice on Cisco administration layer
switch articles based on campus size.