Cisco 2811 Slot Numbering

Cisco

This post explains the interface numbering scheme used in Cisco 1800, Cisco 2800 and Cisco 3800 Series Routers. It also includes line numbering associated with async interfaces.

Table 1-1 Network Module Slots Available on Cisco Access Routers Cisco Router Number of Slots Slot Type Slot Numbering Installation Notes and Limitations Cisco 2600 series 1 Single-wide Slot 1 Does not support extension modules. Cisco 2811 routers 1 Single-wide Slot 1 Does not support extension modules. Cisco 2821 routers 1 Single-wide Extended. Cisco 2811 Integrated services router with AC power, 2 Fast Ethernet Ports, Slots: 1 NME, 4 HWICs, 2 PVDM, 2 AIMs UPP 1. Use accessory kit Double-wide slot—Install a slot divider as described in the 'Installing Slot Dividers in HWIC Slots on Cisco 2811, Cisco 2821, and Cisco 2851 Routers' 31 Oct 2013 You will need a number 2 Phillips screwdriver and a flat-blade Step 7 Disengage the fan from the side attachment slots and push the Cisco 2800 Series Hardware.

Existing router platforms (earlier than Cisco 1800, Cisco 2800, and Cisco 3800) contain a limitation. In some situations, such as when you insert WIC(s) out of order, the configuration of one WIC interface can be lost or applied to another WIC interface.

Example: Assume that you have a serial WIC-2T in WIC slot 1 and WIC slot 0 is empty. The interfaces are named serial 0/0 and serial 0/1. If you insert another WIC-2T into slot 0, the new WIC interfaces are named serial 0/0 and serial 0/1. The old WIC interfaces become serial 0/2 and serial 0/3. Therefore, the old WIC interface configuration moves to the new WIC interfaces.

Refer to How Async Lines are Numbered in Cisco 3600 Series Routers for more information.

In order to overcome this limitation, Cisco 1800, Cisco 2800, and Cisco3800 series platforms now have a three-tiered interface numbering format (slot/subslot/port) for interfaces on WIC slots only.

Note: The slot information for the Cisco 3800 series is the same as the 2800/1800 interface and line numbering. See New Interface and Line Number Conventions for information on interface and line numbering.

New Interface and Line Number Conventions

This section describes the new conventions for interface and line numbering.

  1. The interface numbering scheme is the same for async interfaces and non-async interfaces. To configure the line associated with an async interface, use the interface number to specify the async line.For example, line 0/0/0 specifies the line associated with interface serial 0/0/0 on a WIC-2A/S in slot 0. Similarly, line 0/1/1 specifies the line associated with interface async 0/1/1 on a WIC-2AM in slot 1.

    Note: This document uses the following words interchangeably:

    • Network-module-slot and slot.
    • Interface-card-slot and subslot.
  2. Ports on network modules are numbered like this:interface-number = network-module-slot/port

    OR

    interface-number = slot/port

  3. Ports on interface cards (such as WICs, VWICs and HWICs) installed directly in chassis slots is given here:interface-number = 0/interface-card-slot/port

    OR

    interface-number = 0/subslot/port

  4. This numbering convention is used for ports on interface cards that are installed in network module slots:interface-number = network-module-slot/interface-card-slot/port

    OR

    interface-number = slot/subslot/port

    Note: The slot/subslot/port format only applies to WIC interfaces. Interfaces that are native to the network modules still use only the slot/port format. That is:

    • <interface-name> slot/port is used whenever the interfaces are native on the network module.
    • <interface-name> slot/subslot/port is used whenever the interfaces are on the WIC slot of a network module (NM).
  5. Here is an example for numbering when the motherboard slot number is always 0. The native interfaces on the motherboard are numbered like this:
    • Fa0/0, Fa0/1 on Cisco 2811.
    • Gi0/0, and Gi0/1 on Cisco 2821 and Cisco 2851.

    The Motherboard WIC slots are numbered from 0 to 3. The number increments from right to left, and from bottom to top.

  6. Slot numbers for other slots increase from bottom to top, then right to left. Subslot numbers and port numbers within a slot also increase from bottom to top, then right to left.

Examples

Interfaces native to an extension network module (ENM):

If the ENM carries WIC cards, the WIC slot numbers start from 0:

The extension voice module (EVM) slot analog interfaces are numbered from voice-port 2/0/0 to voice-port 2/0/23, following the NM-HDA convention.

Interface Numbering

This section lists the interface numbering details for Cisco routers.

Table 1 – Interface Numbering on Cisco 1841

Cisco 2811 Slot Numbering Tool

Cisco 2851 Platform

Figure 2 shows the interface numbering on Cisco 2851 platform with:

  • HWIC-1GE in WIC slot 0.
  • HWIC-4T in WIC slot 1.
  • WIC-1SHDSL in WIC slot 2.
  • VWIC-2MFT-T1 in WIC slot 3.
  • NMD-36ESW in ENM slot 1 and EVM-HD-8FXS/DID in EVM slot.

Figure 2 – Interface Numbering on Cisco 2851 Platform

Slots on Cisco 1841, 2801, 2811, 2821, 2851 Routers

This section illustrates the positions of the various slots on Cisco 1841, 2801, 2811, 2821, 2851 routers.

Figure 3 – Rear Panel of the Cisco 1841 Router

Example 2

To configure port 0 of a WIC-2A/S in HWIC slot 3, enter:

Example 3

When you use async interfaces, such as an NM-32A, the lines are listed as slot/num.

The show line command output is explained here:

  • The “Tty” column displays the interface number (which is the same number we use to identify the line).
  • The “Line” column displays the actual line number. The actual line number associated with each interface is determined by complicated equations that vary according to the hardware setup (such as a network module, interface card or interface card in a network module).On these platforms, the line numbers have limited significance. The same can be used in the reverse telnet process. Ideally, rotary under the line configuration should be widely used for reverse telnet applications.
  • For asynchronous or synchronous ports, such as those on the WIC-2A/S, NM-4A/S, NM-8A/S, and NM-16A/S, you must enter the physical-layer async command in serial interface configuration mode before the associated async line can appear in the show line command output (see Example 2).

http://www.cisco.com/c/en/us/support/docs/routers/3725-multiservice-access-router/62611-c2800-62611.html

Centriq Training

Cisco 2811 Slot Numbering System

One of the questions I get from my Routing & Switching students almost every week is, “Why is my first FastEthernet interface called FastEthernet 0/0, and not just FastEthernet 0?” Let’s break this down.

Cisco 2811 Slot Numbering Software

The first thing you need to remember is the convention: slot#/port#. With this convention it is indicating from less to more specific which port you are referencing. The slot can be the device itself or a slot for HWICs (High-Speed WAN Interface Card) or NMEs (Enhanced Network Module). By default non-modular devices, or switches and routers that have no extra slots for HWICs or NMEs, have only one slot, slot 0. So all interfaces will be in slot 0, such as FastEthernet 0/0 or FastEthernet 0/24. Devices that have expansion slots also have slot 0, that is their built in ports. When you start plugging in modules, they become slots 1,2,3, and so on. So with slot you are indicating where the port is, either on the device, or on a card on the device. Then comes the port number. So if I tell you to go configure port GigabitEthernet 0/23 on a switch, you know that it is a built in port, and it is the twenty-third one in. Here is an example of a 2811 router, with its built in ports and slots.

Now, when you start adding in slots, it does get a little interesting. What you have to remember for the naming is right to left / bottom to top. For example, when you look at a 2811 router, it has 4 HWIC interfaces. If you were to plug a module into each one, when the router booted up it would discover all 4. The bottom-right HWIC would be slot 0, the bottom-left would be slot 1, the top-right would be slot 2, and the top-left would be slot 3. So let’s suppose we plug an HWIC into slot 0 with two FastEthernet interfaces. Now we run into a problem because we can’t just use FastEthernet 0/0 to reference the first port. That would reference the port built into the router itself.

So when you are referencing the slots, the convention changes. Now it is: slot#/subslot#/port#. So to get to that first interface we would say FastEthernet 0/0/0, because it is in slot 0 (on the router), subslot 0 (first subslot), port 0 (first interface on the slot). You might also say FastEthernet 0/3/1. Same router, fourth HWIC, second port. If you only have one device, the slot number will always be 0. If you were to have multiple devices in a chassis setup, the slot number will now reference which of the devices you’re modifying. You might see a port FastEthernet 3/3/0. That would be slot 3 (for the third device), subslot 3 (third module on the device), port 0 (first interface on the slot). So the convention expands to account for more complex setups, but it is still referencing least specific down to most specific. Here is an example of a Cisco 7505 setup with multiple slots.

You can see here the device will recognize multiple slots and their ports. If you wanted to configure the 100VG port in the top right, you would use the command #interface vg 3/1/0 to access it. Slot 3, subslot 1, and port 0.

The easy way to figure out what interfaces your device recognizes will be to use the #show ip interface brief command. This will list all interfaces in the order recognized by the device. At boot time as part of the POST (power on self test) is the interface discovery process. As it powers on the device checks all built-in as well as HWIC and NME slots for installed modules. If it finds one, it powers the module and adds the interfaces to the available configuration. Usually the order will be the built-in interfaces and then the modules in the order of the display.

In conclusion, the naming convention is there to help you identify exactly which interface you are configuring, and where it is physically located. Which slot and port, or which chassis slot, subslot, and port. Just keep in mind less to more specific, and right-to-left, bottom-to-top.

Cisco 2811 Slot Numbering

View Centriq’s Routing & Switching Classes Here

This blog was written by Andrew Stibbards, an Instructor at Sunset Learning Institute. Sunset is one of Centriq’s strategic partners.

Cisco 2811 Slot Numbering Systems

Centriq Training has been committed to the growth and development of the Midwest’s IT workforce since 1989.

Cisco 2811 Async Port Numbering

We are the only technology training provider in the area that offers a comprehensive schedule of “Instructor-in-the-Classroom” training classes. Students tell us what an advantage it is to have not only the instructor – but also other IT Professionals – physically in the classroom with you.

If you can’t make it to our facility based in the Kansas City area, you can experience our world class instructors through Live Virtual Class training or Custom/Private Classes delivered at your office.