interface fastehernet on router 831

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May 25th, 2007
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i want set ip adress to fastethernet port cisco 831 router, but he give this msg:

IP addresses may not be configured on L2 links.

how can i solve this plz.

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Richard Burts Fri, 05/25/2007 - 06:59
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The 831 router includes the fastethernet ports in a small switch. So the fastethernet interfaces are layer 2 switch ports and you can not configure IP addresses on layer 2 ports. There is a VLAN interface and it is on the VLAN interface that you configure the IP address.



yoyo_the_king Fri, 05/25/2007 - 07:09
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i want connect this router with 2 network.

how can i do this.

what interfaces must be configured?

maybe eth 0 and eth 1 ?????

nikolay-shopik Fri, 05/25/2007 - 07:17
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You are talkin about external and internal network? If so you need configure FA4 interface and Vlan 1 interface ip address that's it

yoyo_the_king Fri, 05/25/2007 - 07:22
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yes, but there isn't possibility to configure vlan.

he don't accept "interf vlan" command.

nikolay-shopik Fri, 05/25/2007 - 07:24
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what it answerers on command

interface ?

what type of interfaces its support?

yoyo_the_king Fri, 05/25/2007 - 07:28
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this is the answer of "interf ?" :

async , BVI , CDMA-Ix , CTunnel , Dialer , Ethernet , FastEthernet , Group-Async , Lex , Loopback , Multilink , Null , Tunnel , Vif , Virtual-PPP , Virtual-Template , Virtual-TokenRing , range.

yoyo_the_king Fri, 05/25/2007 - 08:01
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this is the result of sh vers:

sh ver

Cisco IOS Software, C831 Software (C831-K9O3SY6-M), Version 12.4(11)T1, RELEASE SOFTWARE (fc5)

Technical Support:

Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Fri 26-Jan-07 00:07 by prod_rel_team

ROM: System Bootstrap, Version 12.2(11r)YV5, RELEASE SOFTWARE (fc1)

Router uptime is 1 hour, 38 minutes

System returned to ROM by power-on

System image file is "flash:c831-k9o3sy6-mz.124-11.T1.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:


If you require further assistance please contact us by sending email to

[email protected].

Cisco C831 (MPC857DSL) processor (revision 0x500) with 58983K/6553K bytes of memory.

Processor board ID FOC10154UCF (1088755702), with hardware revision 0000

Chassis serial number FCZ1017201J

CPU rev number 7

3 Ethernet interfaces

4 FastEthernet interfaces

128K bytes of NVRAM.

12288K bytes of processor board System flash (Read/Write)

2048K bytes of processor board Web flash (Read/Write)

Configuration register is 0x2102


nikolay-shopik Fri, 05/25/2007 - 08:21
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I suppose you have three L3 interfaces with name E0, E1, E2 and four FA0-4 interfaces on back of your router is that correct?

if so do - sh ip int bri

E0 should same range as all FA ports

E1 will be your external port

yoyo_the_king Fri, 05/25/2007 - 08:28
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yes it's right,

plz, haw can'i connect the router and what interface i must configure?

nikolay-shopik Fri, 05/25/2007 - 08:35
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configure E0 as your internal IF, and E1 as your external IF.

As I remeber E0 share connectivity with FA ports on this model. just try setup ip address on E0 interface connect something on any FA ports and ping E0 IF.

yoyo_the_king Fri, 05/25/2007 - 09:39
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1)i configure eth0 with

and i connect pc1 to this interface with

2)i configure eth1 with

and i connect pc2 to this interface with

each pc ping his interface.

but i can't ping pc1 from pc2 or inverse.


yoyo_the_king Wed, 05/30/2007 - 01:48
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1)i configure eth0 with

2)i configure eth1 with

i can ping eth0 and eth1.

if i do "telnet" it 's work fine

but with "telnet" that's not work.

i don't know if it is normal or no.


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