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Community Member

about cisco 831 router interfaces

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.

14 REPLIES
VIP Super Bronze

Re: about cisco 831 router interfaces

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

Community Member

Re: about cisco 831 router interfaces

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)

VIP Super Bronze

Re: about cisco 831 router interfaces

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

Community Member

Re: about cisco 831 router interfaces

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?

Community Member

Re: about cisco 831 router interfaces

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.

Community Member

Re: about cisco 831 router interfaces

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.

Community Member

Re: about cisco 831 router interfaces

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

Community Member

Re: about cisco 831 router interfaces

Hi,

Thanks a lot.

Community Member

Re: about cisco 831 router interfaces

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.

Community Member

Re: about cisco 831 router interfaces

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 ?

Community Member

about cisco 831 router interfaces

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

Community Member

about cisco 831 router interfaces

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->#

Community Member

about cisco 831 router interfaces

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
compliance with U.S. and local country laws. By using this product you
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#

Community Member

Re: about cisco 831 router interfaces

How do I make it show all my ports? when I plug in something to port 1-4 it shows me on the log that I plug in to e0!

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