Cisco 877 can't connect to internet

[johnmeade]

Hello All,

Have received a Cisco 877 ADSL router and went through the set-up. I thought all had gone well however when I connect my router the ADSL and the PPP light comes on  but I am unable to access the Internet or even resolve a web address. As I am new to configuring Cisco routers I was wondering if someone could be so kind as to check my running configuration and point me in the right direction as to what I am missing or have done incorrectly.

Thanks in advance

John

[andrewswanson · Accepted solution]

hello
configure a default route:

ip route 0.0.0.0 0.0.0.0 Dialer0

also add the following for mtu

interface Vlan1
ip tcp adjust-mss 1452
!
interface Dialer0
ip mtu 1492

more info in cisco doc:

http://www.cisco.com/en/US/tech/tk175/tk15/technologies_configuration_example09186a008071a729.shtml

hth
andy

[johnmeade]

Hello Andy,

Thanks for the help I will make the neccesary changes when i get back on Monday and hopefully all will be well.

John

[paolo bevilacqua · Accepted solution]

interface Dialer0
 ip mtu 1492

That's ok, but

mtu 1492

is even better, as it save some packets exchange in PPP negotiation.

[johnmeade]

Hello Andy / Paolo,

Thanks for your suggestions which i have since tried to no avail. I have since then followed the following guide with similar results. This along with many other guides insist on configuring ethernet 0 however on the 877 if i try to configure FastEthernet 0 (there is no ethernet 0 interface) i get an unable to configure L2 interfaces and can only configure Vlan1. It is as if i havent selected some config option that allows internal ip to reach external interface.

The closest i have got is modifying a config someone posted here which at least from the router resolves addresses even if it cannot succesfully ping them i am thinking i have messed up a route or something. I have included the config i think is the closest to working here but am more than happy to wipe it all and start again if that is required.

[johnlloyd_13 · Accepted solution]

Hi John,

Try to put under Dialer0 interface the "ip address negotiated" command and try again.

Sent from Cisco Technical Support iPhone App

[johnmeade]

Hello John,

Thank you after changing it to negotiated it worked.

I would just like to say thank you to all 3 who provided me with help it is much appreciated.

John