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1721 with ADSL - Clients unable to resolve DNS

luke.hurst
Level 1
Level 1

Hi,

I am fairly new to Cisco so please forgive my lack of knowldege on what might be quite a simple problem.

I have a Cisco 1721 router with an ADSL wic. I have followed guides on the Cisco website so that I can connect the router to my home adsl connection. The router connects to my broadband provider and sucesfully obtains an IP address along with Dynamically assigned DNS servers. I am able to ping google.co.uk from the router but not from clients attached via DHCP.

I have noticed that if I ping the IP address of google.co.uk from a client it resolves but it will not resolve the name. This would lead me to believe that the problem lies with DNS resolution/forwarding but I do not know how to investigate further.

Any help would be appreciated. Here is the config;

Thanks, Luke

Building configuration...

Current configuration : 1674 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname Cisco_1721
!
boot-start-marker
boot-end-marker
!
enable secret 5
!
no aaa new-model
ip cef
!
!
ip auth-proxy max-nodata-conns 3
ip admission max-nodata-conns 3
no ip dhcp use vrf connected
ip dhcp excluded-address 192.168.1.1 192.168.1.20
!
ip dhcp pool DHCP-POOL
   network 192.168.1.0 255.255.255.0
   default-router 192.168.1.1
   dns-server 192.168.1.1
!
!
!
!
!
!
!
!
!
!
!
!
interface ATM0
description Outside interface to WAN
no ip address
no atm ilmi-keepalive
dsl operating-mode auto
pvc 0/38
  encapsulation aal5mux ppp dialer
  dialer pool-member 1
!
!
interface Ethernet0
no ip address
shutdown
half-duplex
!
interface FastEthernet0
description Inside interface to LAN
ip address 192.168.1.1 255.255.255.0
ip nat inside
ip virtual-reassembly
speed auto
!
interface Dialer1
description Outside interface to WAN
ip address negotiated
ip nat outside
ip virtual-reassembly
encapsulation ppp
dialer pool 1
ppp chap hostname
ppp chap password 7
ppp pap sent-username ############## password 7 #############
ppp ipcp dns request
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 Dialer1
!
no ip http server
no ip http secure-server
ip nat inside source list 1 interface Dialer1 overload
!
access-list 1 permit 192.168.1.0 0.0.0.255
!
control-plane
!
!
line con 0
password 7 ##############
login
line aux 0
line vty 0 4
password 7 ##############
login
!
end

3 Replies 3

Hi,

I couldn't find the DNS server you're getting from the sevrice provider...

Please add this two command:

configure terminal

ip domain lookup
ip name-server 4.4.4.4

Regards

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Hi,

Thanks for replying.

I have tried your suggestion but the clients are still unable to resolve a hostname when performing a ping. Specifying an IP address works though.

Problem resolved.

I spent quite some time studying example configurations and I spotted that I hadn't enabled the dns service on the router. Quite a simple mistake in the end.

ip dns server

Luke.

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