Cisco Router ISR 3900

About the Cisco 3900 Series ISR

The Cisco 3900 Series Integrated Services Routers are modular branch-office platforms
built to run data, voice, security and application services on a single chassis. Four
platforms make up the range — the 3925 and 3945, and their enhanced
counterparts the 3925E and 3945E — and every one of them takes service modules
in its own right: Enhanced High-Speed WAN Interface Cards (EHWIC), Service Modules (SM),
Packet Voice DSP Modules (PVDM3) and the Service Performance Engine that sets the router's
forwarding capacity.

What makes this range confusing to buy is that the same platform is sold in several
service bundles, each with a different set of features already licensed. The bundle
is indicated in the part number, and buying the right one up front is considerably cheaper
than adding licences afterwards. The bundles you will see on this page are:

• Base (CISCO3925/K9) — the router itself, no voice or security
  licence pack.


• SEC — adds a Security Licence PAK to the base platform.


• V — adds a Unified Communications voice Licence PAK and a PVDM3-64 voice DSP
  module.


• VSEC — combines both: voice and security licensing on one chassis.


• VSEC-SRE — as VSEC, plus a Services Ready Engine module (SRE 700 or SRE 900)
  for hosting applications on the router.


• CME-SRST — voice bundle with CallManager Express and Survivable Remote Site
  Telephony licensing (FL-CME-SRST-25) for up to 25 phones.


• VSEC-CUBE — VSEC plus a Cisco Unified Border Element (CUBE) session licence
  (FL-CUBEE-25) for SIP trunk termination.


• HSEC+ — high-security bundle with a VPN Internal Service Module for hardware
  accelerated encryption.

Every platform runs the same IOS software image family, so the choice between a 3925 and
a 3945 comes down to slot count, services-engine capacity and headroom.

How to Choose a Cisco 3900 Series Router

1. Platform: 3925 or 3945?

The 3925 carries a 3 x GE onboard WAN configuration with 4 EHWIC slots and 4 DSP
slots. The 3945 has the same slot count but a higher-capacity services engine. Where
your requirement is a branch with moderate throughput, the 3925 is the usual pick; where
the router must also run services-heavy configurations, the 3945's extra processing
headroom is worth the difference.

2. Do you need the E platform?

The 3925E and 3945E are the enhanced versions, and the differences are
tangible: a faster services engine, 4 x GE onboard instead of 3, a re-configured
slot layout (3 EHWIC + 3 DSP + 2 SM on the 3925E) and higher default memory. Choose an E
platform where the router will terminate VPN tunnels, run voice for a larger site, or
where you want the extra service-module capacity later.

3. Which Service Performance Engine?

The Services Performance Engine (SPE) is a field-replaceable module that defines how much
the platform can actually forward. Four capacities exist:

• SPE100 — standard on the 3925


• SPE150 — standard on the 3945


• SPE200 — standard on the 3925E


• SPE250 — standard on the 3945E

The SPE can be ordered separately as an upgrade for an existing chassis, which is why
four SPE part numbers appear alongside the routers on this page.

4. Which service bundle?

Match the suffix to what the site must do, not to what it might do later — licences
already bundled are materially cheaper than those bought separately:

• Data only → base model


• Site-to-site VPN or zone-based firewall → SEC


• IP telephony on the branch → V (or CME-SRST if the router runs the call
  control itself)


• Both voice and security → VSEC


• Voice, security and on-router applications → VSEC-SRE


• SIP trunking to the provider → VSEC-CUBE


• Hardware-accelerated encryption → HSEC+

Cisco 3900 Series Model Comparison

Prices are our current selling prices in US dollars, excluding shipping.
Click a model number for the full specification table and availability.

Service Performance Engine upgrades

The SPE is replaceable in the field, so an existing 3925 or 3945 can be lifted to a higher
capacity without replacing the chassis:

Frequently Asked Questions

What is the difference between the 3925 and the 3925E?

The E platforms are the enhanced versions of the same router. The 3925E moves to a
SPE200 services engine (against the 3925's SPE100), changes the onboard WAN to
4 x GE, and re-arranges the slots to 3 EHWIC + 3 DSP + 2 Service Module slots. In
short: more forwarding capacity, one more onboard Gigabit port and a different expansion
mix.

How do I tell which service bundle a router includes?

From the part number suffix. -V indicates a voice bundle, -SEC a security
licence pack, -VSEC both, -VSEC-SRE adds a Services Ready Engine,
-CME-SRST adds CallManager Express and SRST licensing, -VSEC-CUBE adds a
Unified Border Element licence, and HSEC+ adds a VPN Internal Service Module for
hardware-accelerated encryption. A model with no suffix is the base platform.

Can I upgrade an existing router instead of buying a new one?

Two components are field-replaceable. The Services Performance Engine can be swapped
to a higher capacity module (SPE100 → SPE200, for example), and memory and voice DSP modules
can be added. Service licences, however, are ordered by part number, so if the router was
bought without a voice or security licence pack it is generally more economical to move to a
bundle model than to license the existing chassis.

Are the voice bundles supplied with a DSP module?

Yes — the V, VSEC, VSEC-SRE, VSEC-CUBE and CME-SRST
bundles all include a PVDM3-64 voice DSP module, which provides the conference and
transcoding resources the voice features require. The base and SEC models do not.

What does the SRE module give me?

The Services Ready Engine (SRE 700 on the 3925 series, SRE 900 on the 3945 series in these
bundles) is a blade that runs applications directly inside the router — branch caching,
virtualised services and similar workloads — so they do not have to be hosted on a separate
server at the site.

Do you supply the EHWIC and SM modules as well?

Yes. Give us the router model and the interface mix you need — WAN cards, switching
modules, voice cards or DSP modules — and we will quote the complete configuration.