Cisco 1700 Router

Discussion in 'Cisco' started by Charles StClair, Jul 25, 2008.

  1. I have configured my Cisco 1700 router to access the Internet through my
    Westell Model 6100 modem using a 1ENET WIC. I can ping my modem at but I am unable to access the Internet through my router. The
    Internet passes through the 1ENET and my LAN is on the FastEthernet0. My
    configuration of my router is below:

    ! ******************************************************************
    ! Cisco1720.cfg - Cisco router configuration file
    ! Automatically created by Cisco ConfigMaker v2.6 Build 6
    ! Friday, July 25, 2008, 07:59:40 AM
    ! Hostname: Cisco1720
    ! Model: 1720
    ! ******************************************************************
    service timestamps debug uptime
    service timestamps log uptime
    service password-encryption
    no service tcp-small-servers
    no service udp-small-servers
    hostname Cisco1720
    enable password char0912
    no ip name-server
    ip subnet-zero
    no ip domain-lookup
    ip routing
    interface FastEthernet 0
    no shutdown
    description connected to EthernetLAN
    ip address
    ip nat inside
    keepalive 10
    interface Ethernet 0
    no shutdown
    description connected to Internet
    ip address
    ip nat outside
    keepalive 10
    ! Access Control List 1
    no access-list 1
    access-list 1 permit
    ! Dynamic NAT
    ip nat translation timeout 86400
    ip nat translation tcp-timeout 86400
    ip nat translation udp-timeout 300
    ip nat translation dns-timeout 60
    ip nat translation finrst-timeout 60
    ip nat inside source list 1 interface Ethernet 0 overload
    router rip
    version 2
    passive-interface Ethernet 0
    no auto-summary
    ip classless
    ! IP Static Routes
    ip route Ethernet 0
    no ip http server
    snmp-server community public RO
    no snmp-server location
    no snmp-server contact
    line console 0
    exec-timeout 0 0
    password kc9bzf
    line vty 0 4
    password kc9bzf
    Any help would be greatly appreciated.
    Charles StClair, Jul 25, 2008
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  2. Charles StClair

    braydonsdad Guest

    Could your access-list for NAT possibly be being ignored?

    no access-list 1
    access-list 1 permit
    braydonsdad, Jul 25, 2008
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  3. Charles StClair

    Scott Perry Guest

    No, the configuration, as read from top to bottom, would first eliminate any
    access-list 1 and then secondly would build the access-list.
    Scott Perry, Jul 25, 2008
  4. Charles StClair

    Scott Perry Guest

    I must consider your modem to be a router which provides PPPoE, DNS proxy
    and NAT services. Sorry about being picky on the terminology but it makes a
    big difference!

    I ran your Cisco 1720 router configuration through a 2600 series router and
    it worked. I did consider that some sections could be improved to my
    preference, but I cannot debate that it did perform NAT and allow inside
    access to the outide.
    The additional solutions that I see not only deal with your routing, but
    also that you do not provide DHCP to your inside hosts which the "modem"
    would have done. You need to make sure that DNS resolution works for your
    inside systems as well. Without DNS resolution, only connections to
    specific IP addresses will work, not connections to systems based on fully
    qualified domain name (FQDN) like

    Below are the sections, "routing", "dhcp", and "advice" which make up the
    remainder of this posting.

    This default route points out interface Ethernet0, but it does not specify
    the next hop. Think like your router: how does it know what IP address on
    Ethernet0 the traffic will be routed to out of the 256 IP addresses in that
    subnet on interface Ethernet0? Help your router out by making a more
    specific default route:
    no ip route Ethernet0
    ip route
    no ip route Ethernet0
    ip route Ethernet0

    How do your inside hosts know what IP address information to use?
    How do your inside hosts know what DNS server to use? Your "modem" is
    performing DNS proxy.
    I think that is your current problem. Your inside PC may be trying to web
    browse some Internet FQDN and is not resolving it to an IP address. Try
    throwing this DHCP configuration in place:
    ip dhcp excluded-address
    ip dhcp pool insidelan
    This will enable the Cisco 1720 router to act as a DHCP server for DHCP
    requests from the interface facing the network,
    which is FastEthernet 0. Change the domain-name as you like. Now your
    inside PCs can lease an IP address and have the correct DNS server

    The Westell modem appears to have a bridging mode which you might want to
    take into consideration. Based on what I read, it appears that you will be
    configuring the Cisco 1720 router to do percisely what the Westell
    modem/router is doing: route to the Internet using NAT.
    No more posting passwords in your configuration!
    Scott Perry, Jul 25, 2008
  5. Charles StClair


    May 8, 2012
    Likes Received:
    Perhaps I can get help on this scenario?

    Cisco 1720 was configured only for intranet.
    Now we need one remotely located PC WinXP to access internet

    Remote PC IP NIC is, gateway is, with IP provider DNS's
    Cisco Remote 1720 IP is
    Local Cisco 1720 IP is
    The local internet gateway (linksys WRV54G) IP is

    We use all static IP's and are unable to ping to I opened the linksys and added the route mask and we can ping it now.

    But we can still not ping an internet ip such as google's and we will need to use the DNS's for internet lookups.

    Thanks in Advance for any help it would be greatly appreciated.
    PeterDCS, May 8, 2012
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