about cisco 831 router interfaces

cisco8123 · ‎04-17-2010

Hi, I am new and have a dummy question on a cisco 831 router.

I only see 4 fast ethernet interfaces and 1 ethernet interface on the back of the router.

however, the "show version" command shows the following:

Cisco C831 (MPC857DSL) processor (revision 0x500) with 58983K/6553K bytes of memory.
Processor board ID FOC10221TUU (2878649209), with hardware revision 0000
Chassis serial number FHK102422KM
CPU rev number 7
3 Ethernet interfaces
4 FastEthernet interfaces

Why it says 3 Ethernet interfaces?

Thanks.

Reza Sharifi · ‎04-17-2010

cisco8123 wrote:

Hi, I am new and have a dummy question on a cisco 831 router.

I only see 4 fast ethernet interfaces and 1 ethernet interface on the back of the router.

however, the "show version" command shows the following:

Cisco C831 (MPC857DSL) processor (revision 0x500) with 58983K/6553K bytes of memory.
Processor board ID FOC10221TUU (2878649209), with hardware revision 0000
Chassis serial number FHK102422KM
CPU rev number 7
3 Ethernet interfaces
4 FastEthernet interfaces

Why it says 3 Ethernet interfaces?

Thanks.

Hi,

You are correct. The 831 comes with four-port 10/100BASE-T with autosensing MDI/MDX for autocrossover and one 10BASE-T Ethernet for WAN.

There may be bug in the IOS that causing it showing 3 Ethernet. What ver are you running?

HTH

Reza

cisco8123 · ‎04-17-2010

Thanks for help.

here is the version of my ios:

Cisco IOS Software, C831 Software (C831-K9O3Y6-M), Version 12.4(9)T1, RELEASE SOFTWARE (fc2)

Reza Sharifi · ‎04-17-2010

Hi,

I do not see 12.4(9)T1 in the list of IOS posted on CCO. I see 12.4.(9)T3. T4, T5, etc... with the latest being 12.4.15T13(MD)

You may want to upgrade to one of theses images and see the problem still exist.

HTH

Reza

Steven Tolzmann · ‎04-18-2010

It it isn't causing any problems with the operation of the Router, I would just leave the IOS alone. Its probably just a cosmetic glitch.

But yes you are correct... The 831 has 1 10base-t ethernet wan port, and 4 10/100 switch ports.

If you do a "show run", does only one Ethernet interface appear in your config?

cisco8123 · ‎04-19-2010

the output of "show run" is as follows:

interface Ethernet0
description $ETH-LAN$$ETH-SW-LAUNCH$$INTF-INFO-Ethernet 10/100$
ip address 10.10.10.1 255.255.255.248
!
interface Ethernet1
no ip address
shutdown
duplex auto
!
interface Ethernet2
no ip address
shutdown
!
interface FastEthernet1
duplex auto
speed auto
!
interface FastEthernet2
duplex auto
speed auto
!
interface FastEthernet3
duplex auto
speed auto
!
interface FastEthernet4
duplex auto
speed auto

It shows 3 Ethernet interfaces and 4 fast ethernet interfaces, which confused me.

Steven Tolzmann · ‎04-19-2010

Wow that really is weird if its showing in the running-config...... Probably a buggy IOS?

If it ever causes problems, see if you can re-flash the ios.

bkoyip · ‎05-02-2010

Hi cisco8123

I have a 831 as well and don't worry about the E2 and this is not relate to your IOS or not a defective router.

E0 = LAN = 4 port FE non-manage switch. (Can't make any config on a FE interface, controller by the E0.)

E1 = WAN

E2 possible for AUX use but port not existing physical, more likely is the controller including this ethernet but not physical appear.

RogerC

cisco8123 · ‎05-03-2010

Hi,

Thanks a lot.

stevjarbeck · ‎04-19-2010

Do you have enough memory to properly run the IOS that you are? I seen goofy things happen when you try and "shoe horn" an IOS into a router that can't run it.

rtalipinani · ‎06-15-2010

I have the very same output on my C831. Here are the show commands:

show run:

!
interface Ethernet0
ip address 10.10.0.2 255.255.255.0
hold-queue 100 out
!
interface Ethernet1
no ip address
duplex auto
!
interface Ethernet2
no ip address
shutdown
!
interface FastEthernet1
duplex auto
speed auto
!
interface FastEthernet2
duplex auto
speed auto
!
interface FastEthernet3
duplex auto
speed auto
!
interface FastEthernet4
duplex auto
speed auto
!

sh ip int brief:

Interface                      IP-Address      OK? Method   Status               Protocol
FastEthernet1              unassigned     YES unset      up                    up
FastEthernet2              unassigned     YES unset      down                down
FastEthernet3              unassigned     YES unset      down                down
FastEthernet4              unassigned     YES unset      down                down
Ethernet0                    10.10.0.2         YES NVRAM up                    up
Ethernet1                    unassigned      YES NVRAM up                    down
Ethernet2                    unassigned      YES NVRAM administratively down down

From what I understand from other posts here... The internal wiring could be this way

||

E0

_______||______

|| || || ||

Fa Fa Fa Fa

1 2 3 4

Any comments ?

ts-stg · ‎09-18-2019

Normal Operation, Keep Eth 2 on shutdown, Router Funktion (L3) between E0 and E1 and for Swiching (L2) behave like that on E0 there is a 5 port Switch attached but the uplink (5th.Port) acts as Uplink Interface that cannot be configured, so it has not name attached

WAN

E1

|| (Routing - Function)

E0

______||______

|| || || ||

Fa Fa Fa Fa

1 2 3 4
DMZ operation, two separate LANs, Eth 2 on no shutdown

WAN

E1

|| (Routing - Function)

E0 E2

____||____ ||

|| || || ||

Fa Fa Fa Fa

1 2 3 4
see https://www.cisco.com/en/US/docs/ios/12_3/12_3x/release/notes/rn800xr.html#wp90349

ivan.polak · ‎01-20-2012

Hi cisco8123,

You can see 3x Ethernet ports because of:

1 WAN Etrhernet Port

1 Virtual Ethernet Port representing L3 interface for your LAN

1 Virtual Ethernet Port representing DMZ interface on your LAN

Hope it helps.

Cheers

Ivan

jkinnaird1 · ‎04-01-2012

Hi,

My C831 aligns them this way

E0 - Fast ethernet 1,2 and 3

E1 - Internet Port

E2 - Fast Ethernet 4

See below

e Fri Mar 1 2002, configured from console by console.

*Mar 1 00:00:18.283: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state to up

*Mar 1 00:00:18.283: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet1, changed state to down

*Mar 1 00:00:19.311: %LINK-3-UPDOWN: Interface FastEthernet1, changed state to down

*Mar 1 00:00:19.311: %LINK-3-UPDOWN: Interface FastEthernet2, changed state to down

*Mar 1 00:00:19.315: %LINK-3-UPDOWN: Interface FastEthernet3, changed state to down

*Mar 1 00:00:19.811: %SYS-5-CONFIG_I: Configured from memory by console

*Mar 1 00:00:20.635: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1, changed state to down

*Mar 1 00:00:20.635: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet2, changed state to down

*Mar 1 00:00:20.635: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet3, changed state to down

*Mar 1 00:00:22.491: Switch port 4 now connected to e2 interface

*Mar 1 00:00:22.495: %SYS-5-RESTART: System restarted --

Cisco IOS Software, C831 Software (C831-K9O3SY6-M), Version 12.3(8)YA1, RELEASE SOFTWARE (fc1)

Synched to technology version 12.3(9.6)T

a show ip int brief shows all 3 ethernet ports can be used,

John-C831->#a

Interface IP-Address OK? Method Status Protocol

FastEthernet1 unassigned YES unset down down

FastEthernet2 unassigned YES unset up up

FastEthernet3 unassigned YES unset down down

FastEthernet4 unassigned YES unset up up

Ethernet0 192.168.3.1 YES manual up up

Ethernet1 192.168.0.140 YES manual up up

Ethernet2 unassigned YES NVRAM up up

Loopback1 20.20.20.20 YES NVRAM up up

Loopback2 12.12.12.12 YES NVRAM up up

Loopback3 192.168.2.1 YES NVRAM up up

John-C831->#

manasesramos · ‎01-16-2013

Why does mine show this and NOT all 4 ports and 1 wan port?

Manases#sh ver
Cisco Internetwork Operating System Software
IOS (tm) C831 Software (C831-K9O3SY6-M), Version 12.3(2)XA7, RELEASE SOFTWARE (f
c3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by cisco Systems, Inc.
Compiled Tue 25-Mar-08 15:21 by ealyon
Image text-base: 0x800131E8, data-base: 0x80B77E34

ROM: System Bootstrap, Version 12.2(8r)YN, RELEASE SOFTWARE (fc1)
ROM: C831 Software (C831-K9O3SY6-M), Version 12.3(2)XA7, RELEASE SOFTWARE (fc3)

Manases uptime is 52 minutes
System returned to ROM by power-on
System image file is "flash:c831-k9o3sy6-mz.123-2.XA7.bin"

This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
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agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:
http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to
export@cisco.com.

CISCO C831 (MPC857DSL) processor (revision 0x200) with 29492K/3276K bytes of mem
ory.
Processor board ID AMB065100C9 (3557975494), with hardware revision 0000
CPU rev number 7
Bridging software.
2 Ethernet/IEEE 802.3 interface(s)
128K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash (Read/Write)
2048K bytes of processor board Web flash (Read/Write)

Configuration register is 0x2102

Manases#

Manases#sh inter des
Interface Status         Protocol Description
Et0       up             up
Et1       up             down     Internet WAN Port
Manases#sh ip inter bri
Interface                  IP-Address      OK? Method Status                Prot
ocol
Ethernet0                  unassigned      YES NVRAM up                    up

Ethernet1 10.25.50.75 YES DHCP up down

Manases#