Cisco 1841 router and Macbook pro problem

benjamin_a · ‎03-04-2012

Hi

I have this strange problem with my Macbook pro, when I connect it to my cisco 2940 8 port switch then I can reach my ISP (websites eg. google.com) in like 2 minuttes, then something is happening on my router, because suddenly I can´t reach my ISP

This is what I have found out so far:

1. when I lose connection to my ISP then I can only ping internal ip addresses eg. another computer in my network

2. if I renew my ip address on the Macbook then it works again in 2 minutts, then the same happens again.

This is my network setup:

Router -> Switch 1 -> Switch 2

I also know that it is not the Macbook, because it have got a new motherboard, and it have been reinstalled

also if I use the Macbook on a other network then it works fine.

All my other computers ( windows and linux ) works fine, no problems.

To me it looks like it is a Nat and/or DNS problem, but I can´t fine out what it is

If there is any one there have an idea what it is then pls tell

Best regard

Benjamin A

Reza Sharifi · ‎03-04-2012

Hi,

Can you post the config from the router (sh run) and point out what interface connect to what network?

Also, are your switches just used as layer-2 devices?

benjamin_a · ‎03-04-2012

Of course, here it is:

R1#sh run

Building configuration...

Current configuration : 2476 bytes

!

! No configuration change since last restart

!

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname R1

!

boot-start-marker

boot-end-marker

!

enable secret 5 xxxxx

!

aaa new-model

!

aaa authentication login default local

aaa authorization exec default local

!

aaa session-id common

!

resource policy

!

clock calendar-valid

mmi polling-interval 60

no mmi auto-configure

no mmi pvc

mmi snmp-timeout 180

ip subnet-zero

ip cef

!

no ip dhcp use vrf connected

ip dhcp excluded-address 192.168.2.1

ip dhcp excluded-address 192.168.2.2

ip dhcp excluded-address 192.168.2.3

!

ip dhcp pool DHCP-SERVER-LAN-SIDE

network 192.168.2.0 255.255.255.0

default-router 192.168.2.1

dns-server 192.162.153.164 194.239.134.83

domain-name Net

!

ip ssh version 2

!

username xxx secret 5 xxx

username xxx password 0 xxx

!

interface FastEthernet0/0

ip address dhcp

ip nat outside

shutdown

duplex auto

speed auto

no cdp enable

!

interface FastEthernet0/1

ip address 192.168.2.1 255.255.255.0

ip nat inside

duplex auto

speed auto

!

interface Serial0/0/0

no ip address

shutdown

no fair-queue

clockrate 2000000

!

interface ATM0/1/0

no ip address

no atm ilmi-keepalive

dsl operating-mode auto

!

interface ATM0/1/0.1 point-to-point

description Link_To_Outside

ip address dhcp

ip nat outside

logging event subif-link-status

atm route-bridged ip

pvc 0/101

oam-pvc manage

encapsulation aal5snap

!

ip classless

!

no ip http server

no ip http secure-server

ip nat inside source list 1 interface ATM0/1/0.1 overload

!

access-list 1 permit 192.168.2.0 0.0.0.255

!

control-plane

!

banner motd ^C

------------------------------------------------------------ --------------

. .

| |

||| |||

.|| ||. .|| ||.

.:||| | |||:..:||| | |||:.

C i s c o S y s t e m s

Kun For Autoriserede!

------------------------------------------------------------ -------------- ^C

!

line con 0

exec-timeout 0 0

password xxx

logging synchronous

line aux 0

line vty 0 4

logging synchronous

transport preferred none

transport input ssh

!

end

This is how it is connected:

Router =

ATM0/1/0 -> ISP

FastEthernet0/1 -> Switch 1

the switches is just configureted as dum switches @layer 2, the only thing there is been changed on the is spanning tree portfast default.

Hope this helps

Reza Sharifi · ‎03-04-2012

Hi,

Have a look at this discussion and see if it is helpful to you.

https://supportforums.cisco.com/thread/2114266?start=0&tstart=0

HTH

johnlloyd_13 · ‎03-04-2012

Hi Benjamin,

Could you add the "ip route 0.0.0.0 0.0.0.0 dhcp" command and try again?

Sent from Cisco Technical Support iPhone App

benjamin_a · ‎03-05-2012

Hi again

I have now tryed the "ip route 0.0.0.0 0.0.0.0 dhcp", but it didn´t help

I have also read the discussion that you (Reza Sharifi) recommended, but is it not over wifi the problem is

At this point I am lost of idea what it can be, but one thing I found out was that if the Macbook is the only pc on the network, then it works fine ??

Is there how that I can degbu on the router ? I have tryed the degug all, but then my router crashed

benjamin_a · ‎03-05-2012

I think that I have found the problem !

it seems to be the switch 2, I have tested it this way:

1. connected the Macbook to the switch 1 and there was no problem !

2. replaced the switch 2 with at dum cheap D-Link (yes I know it is D-Link ) switch and now it is working, and it have been working the last hours

I will test it to tomorrow, and if it is the switch then

what can be wrong with my cisco 2940 switch ?

would it be better if I make a new post ?

Reza Sharifi · ‎03-05-2012

Thanks for update Ben. If you found the problem, than stay away from the 2940 switch. It could be an IOS bug. Since you are not using it, you can clear the config and load a newer version of IOS and test again. No need for a new post.

HTH