Cisco877 without ADSL ISP connection

Unanswered Question
Feb 5th, 2008
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Hi All,

I have a Cisco 877 with 1 adsl port and 4 fastethernet ports. A cable modem (ISP)is to be connected via RJ45 to one of the Fastethernet ports supplying an internet connection (wrong HW being used I know). Another port will be sitting on an Inside Vlan 1 connected to a PC. A second Inside port will connect to an AP1130 which will provide internet connectivity to wireless laptops. PAT translation will be used from the Inside addresses to the Outside static internet IP. Can anyone tell me whether this network layout is possible and how should the Outside fastethernet interface needs to be configured (as a trunk on a separate native VLAN) to connect the Inside Vlan 1 to the internet?

Thank you

Much appreciated

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Overall Rating: 4.8 (3 ratings)
paolo bevilacqua Tue, 02/05/2008 - 15:19
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Yes this is possible, but you need an "Advanced IP services" image that will let you and additional VLAN on one of the 4 switched ports, where you connect the cable modem.

With the standard image, thta is not possible.

Hope this helps, please rate post if it does!

victor888 Tue, 02/05/2008 - 16:04
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Thanks for the quick reply. So just to clarify how would you configure this interface and corresponding VLAN connecting to the internet?

Could you please provide a generic example?

Thank you

paolo bevilacqua Wed, 02/06/2008 - 01:05
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interface fa0

switchport access vlan 2

interface vlan 2

ip address ...

in nat outside

Thanks for the nice rating and good luck!

paul-d Sat, 11/29/2008 - 10:24
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Hi I have version c870-advipservicesk9-mz.124-4.XC7.bin

but I get a message when i create vlan 2 saying it is not in the database

I normally create vlans using

conf t

vlan 2

but that command is not allowed ?


Jon Marshall Sat, 11/29/2008 - 10:47
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I believe you have to create the vlans in the vlan database rather than from conf t mode. Try

router# vlan database

router(vlan)# vlan 2


paul-d Sat, 11/29/2008 - 10:52
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thanks for the switft reply but that command isnt available on my version.

paul-d Sun, 11/30/2008 - 05:11
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Doh !

you are correct.

I always associate that vlan database with the older versions.

Many thanks !


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