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New Member

Cisco 1841


I am having some issues with the configuration of the WAN connection of a Network with a WAN - RAD-Ethernet of 1024K local ISP access & LAN - Cisco Firewall ASA 5510. Previously, it was using Router 871+ series. Recently my client wants to swap to a higher-end router - 1841. However, when i configure the router, I set Ethernet0/0 to be the LAN connection & it works fine. As for the Ethernet0/1 (WAN connection) IP address to be the same subnet as the RAD ethernet, there is NO connection at all. Unable to figure out what is the real cuase behind it. Can anyone assist please. Appreciate.


Re: Cisco 1841


Please post the configuration of both routers. 871 and 1841.

It could be the case that since you have changed router you have a new mac.adr.

So ask your ISP.



New Member

Re: Cisco 1841

Hi Bjornarsb,

Thanks. here's the cfg for 871 as for 1841, Ethernet0/0 is the LAN & Ethernet0/1 is the WAN. There is NO connection light at the WAN but able to connect to LAN that is to the Firewall.

What do I need to ask my ISP on the Mac Add?

New Member

Re: Cisco 1841

When you was changed the router with 1841,it have a different MAC ADDRESS,so if router is connected directly to your ISP,you should tell em to unlock and obtain new mac address and agin locked up it.

I see you use VLAN1 for lan or administrative monitoring,WAN is not in vlan-membership,so no connectivity between LAN and WAN ?

Re: Cisco 1841


can you try to change the speed and duplex setting on your router end ?

Most of the devices comes with 10Mbps speed and half duplex by default.

May be the compatibility of the speed/duplex settings or even try changing the cable which you are connecting both the devices..

if u still face even after changing the speed/duplex/cable then do post the output of show ip int brief & show interface fa0/1 here.