configure cisco 871 router with public I.P on Vlan 1 and WAN

By contact_abdul ·
I have cisco 871 router.I want to use it for internet.The users will connect to LAN .The wan interface will be configured with public I.P.I got public I.P from ISP.Subnet

The lan side is VLAN 1 (FE 0 to FE3).WAN is FE 4. The cisco router will be gateway for PC users.The PC users want to use ONLY PUBLIC I.PS? ok? same subnet

I want users also use public I.Ps for internet.How can Configure VLAN 1? how should i bridge/route/connect WAN and LAN?? please give full configuration.I am new.

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What ip's are you using for internal traffic?

by cewcathar In reply to configure cisco 871 route ...

My question, are you using private IP's for your internal traffic? Thanks.


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If you are using private ip's in your internal network

by cewcathar In reply to configure cisco 871 route ...

If you use private ip's in your internal network, then you will need to configure NAT (network address translation) on your external router.

That router will then assign ip source addresses--from the address pool you specify--to internet-bound traffic.

That's a nice way to do things, and it keeps the workings of your internal network a bit more private.

As for configuring the VLAN's, vlan 1 is automatically configured if you are using CISCO routers, and any traffic on your switches will automatically join it unless you do something to stop this. If you do not need to subnet the addresses (that is, if your internal network does not need to be divided into different segments) then you will only need a single VLAN. (However I would not use VLAN 1 which is native VLAN--for security reasons; I can talk you through VLAN's I think, by email, but I've never been on a CISCO switch; I've just learned the configurations).

If you have different kinds of traffic at all, I do recommend subnetting.

Best wishes,


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I'm really not sure what you are asking . . . do you need a default gateway

by cewcathar In reply to If you are using private ...

! If you have no routing enabled
! After the command configure terminal
!(global configuration mode)
Router (config)# ip default-gateway x.x.x.x

! x.x.x.x.
! specifies ip address of
! default gateway router
! you would need to get the address
! of the next hop router on the internet
! from your isp
! Alternately you could
! specify the outbound interface.


! The command to use instead of the above
! --if you have routing enabled

RouterM (config)# ip route x.x.x.x

! As far as configuring your WAN interface,
! Is it going to be encapsulated in ppp?
! that would be
Router# Configure terminal
Router (config)# interface #
! # is used to indicate
! the # of the interface
Router (config-if)# encapsulation ppp

! You would then need
! at least one permit statement
! What kind of traffic are you planning on?
! just http, https (web), smtp, pop (email)?
! I'd use permit statements
! for each of those
! and for some icmp packet types
! Nothing else will get through then.
! As far as configuring vlan1 goes,
! it is configured by default
! (though you do have to say no shut down)
! but it's not secure
! You've got to secure it
! I would secure it before getting it going

! How many switches do you have??

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