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How to configure these on Cisco Router 881?

Posted on 2013-12-11
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Last Modified: 2013-12-17
I want to setup this router as an Internet router for the following objectives:

   1. There are 2 interfaces - VLAN1 for internal network, and FE4 as WAN interface for Internet line. I have subscribed a Internet line with the ISP on dynamic IP plan. What I have to configure on the WAN interface is just set it to DHCP, and all ip addressing will be allocated. These include, IP assigned to the WAN interface, subnet mask, default gateway, dns server ips, etc.

      How should set these settings on the FastEthernet4 interface? How about the default gateway? Shall I point it to the FE4 or else?

   2. I also need to setup this router as a DHCP server for my network - 192.168.100.0/24. There are few IPs have been assigned to few servers, and no-changeable. These IPs are,
.100.5, .100.25, .100.144, .100.188; how can I exclude these IPs on my router, suppose my DHCP pool is ranging - .100.51 - .100.200?


thanks in advance.
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Question by:MichaelBalack
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Author Comment

by:MichaelBalack
ID: 39711448
I nearly forget, how to set the NAT on this router?
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Assisted Solution

by:Matt V
Matt V earned 400 total points
ID: 39714804
DHCP Pool:

ip dhcp pool DHCPPOOL
  network 192.168.100.0 255.255.255.0
  default-router 192.168.100.1 (this is your LAN IP of router)
  dns-server x.x.x.x x.x.x.x (specify DNS server here)
 
Allow DCHP to set the default route, specifying the interface does not always work.
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Jody Lemoine earned 1600 total points
ID: 39715028
mattmvotas has covered the basics of your DHCP pool for your VLAN1 clients, but you still need to restrict the pool. Cisco routers assume that they can assign the entire subnet, so to set your pool you need to tell the router what range to exclude. Use the following for a pool of 192.168.51-200.

ip dhcp excluded-address 192.168.100.1 192.168.100.50
ip dhcp excluded-address 192.168.100.201 192.168.100.254

To exclude the individual hosts with static IPv4 addresses, a simplified version of the same command it used. You don't actually need to exclude the first two of these because they're already covered by the ranges used to restrict your DHCP pool.

ip dhcp excluded-address 192.168.100.5
ip dhcp excluded-address 192.168.100.25
ip dhcp excluded-address 192.168.100.144
ip dhcp excluded-address 192.168.100.188

For the WAN interface on FastEthernet4, go with this. The "ip dhcp client request" line is actually a default, but I'm including it to illustrate what's going on.

interface FastEthernet4
 ip address dhcp
 ip dhcp client request router dns-nameserver
 ip dhcp client default-router distance 1
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Author Comment

by:MichaelBalack
ID: 39715649
Hi mattvmotas and jodylemoine,

How about the nat? for vlan1 and fa4?
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Expert Comment

by:Jody Lemoine
ID: 39715653
That's fairly straight-forward.

object-group network og-rfc1918
 10.0.0.0 /8
 172.16.0.0 /12
 192.168.0.0 /16
!
ip access-list extended acl-nat
 permit ip object-group og-rfc1918 any
!
ip nat inside source list acl-nat interface FastEthernet4 overload
!
interface Vlan1
 ip nat inside
!
interface FastEthernet4
 ip nat outside
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Author Comment

by:MichaelBalack
ID: 39715658
Hi jodylemoine,

Thanks for the speedy reply.

Then for the default gateway, is this command: ip route 0.0.0.0 0.0.0.0 interface fastethernet4
works?
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Expert Comment

by:Jody Lemoine
ID: 39715664
If you want to define your default gateway manually, "ip route 0.0.0.0 0.0.0.0 dhcp" will do the trick, but if you're getting the default gateway from DHCP, it shouldn't be needed. I would set up your DHCP connection and do a "show ip route" to see if it has installed the route for you before adding it manually. If you already have a 0.0.0.0/0 route, you don't need to add one.
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Author Closing Comment

by:MichaelBalack
ID: 39725640
Excellence, it works like a charm
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