Clients lose connection to router every 10 to 15 minutes

[wizkok001]

I have a very strange problem. My network has ISP modem from there it has an Cisco 2811 router connected with an Cisco 3550 Switch. All clients are connected to the 3550 switch in multiple vlans. Now the problem is that the clients loses connection every 10 or 15 minutes with the internet. 

if i ping from the client to the modem the connection is restored and i can use the internet on that client. I need to do that for every client. Some how the client doesnt see the dns server anymore until i ping the modem.

When i ping from the router to the modem it working always but doesnt restore the connection on the client i really need to ping from the client to restore the connection...

Cisco router has NAT enabled.

router ospf 1
router-id 1.1.1.1
log-adjacency-changes
passive-interface GigabitEthernet0/0
network 172.16.0.0 0.0.0.3 area 0
network 192.168.178.0 0.0.0.255 area 0
default-information originate
!
ip route 0.0.0.0 0.0.0.0 192.168.178.1

interface GigabitEthernet0/0
ip address 192.168.178.2 255.255.255.0
ip nat outside
ip virtual-reassembly
duplex auto
speed auto
!
interface GigabitEthernet0/1
ip address 172.16.0.1 255.255.255.252
ip nat inside
ip virtual-reassembly
duplex auto
speed auto
!

ip nat pool OUTSIDE-ACCESS 192.168.178.2 192.168.178.200 prefix-length 24
ip nat inside source list 10 pool OUTSIDE-ACCESS

access-list 10 remark == [CLIENT ACCESS INET] ==
access-list 10 permit 172.16.0.0 0.0.0.3
access-list 10 permit 172.16.10.0 0.0.0.31
access-list 10 permit 172.16.20.0 0.0.0.31
access-list 10 permit 172.16.30.0 0.0.0.15
access-list 10 permit 172.16.99.0 0.0.0.15

Can some explain to me what im doing wrong? because i don't see it anymore... this is day 3 and it's getting annoying.. :)

[Richard Burts]

From the description that you give my first guess is that the NAT entry is timing out of is being removed for some reason. I have a couple of questions and suggestions which I hope may help.

- how many clients are in your network?

- how many entries are in your translate table on the router?

- does it have to be a ping to the modem? If you try to ping 8.8.8.8 would the client begin to work?

- when a client has this problem can you execute a show of the translate table with | include <ip_address> to see if there is an entry for that client.

- then after the client has done the ping can you do the show command again of the translate table and see if there is now an entry for the client?

HTH

Rick

[wizkok001]

Hello sorry for the late reaction...

The problem is solved. The ISP forgot to put my ISR in bridge mode. After they demoted the ISP router to just modem my NAT started to work. Everything works great now. The problem was never in the configuration.

thank you for the quick response. 

Just to answer a few of your questions because i tried to get the answers for you. I couldnt ping to 8.8.8.8 i need to ping the default gatewy then the internet comes back.

i have 37 clients in the network at the moment.

translate table was empty when the internet was lost.

no entry for the client on the moment the internet was gone.

With best regards Arjan Zwerver

[Gaurav Mahajan]

Great thanks for update. Ideally as Rick mentioned loosing internet connectivity would have been due to NAT entry timing out on the router.

Here is what could be happening.

What is bridge mode?

Bridge mode is the configuration that disables the NAT feature on the modem and allows a router to function as a DHCP server without an IP Address conflict.

The modem has to be bridged before connecting to a router since applications like VPN, P2P, and remote management require a public IP Address on the router WAN port for a successful connection.

You will need to call your Internet Service Provider for the bridge mode settings.

Thanks,

Gaurav 

[Richard Burts]

Arjan

I am glad to know that the problem is resolved. Thank you for posting back to the forum to let us know about this. The ISP needing to set their device in bridged mode would be a reasonable explanation of these symptoms.

HTH

Rick