case Study - Cisco routing

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Case Study - Routing Issue

Situation: There are two routers in the main office. XO router 192.168.0.250 connecting to the Internet. Cisco 1841 Router 192.168.0.81 connecting to the remote office. All computer use 192.168.0.81 as default gateway so that they can talk to the Internet and remote office. After added a Cisco ASA5510 between the XO router and the LAN, no one can access the Internet any more.

Troubleshooting: 1. If we setup the default gateway pointing to the ASA5510 192.168.0.250, the computer can access the Internet, but not the remote office. So, the ASA5510 is connecting to the Internet but not route back to the remote office.

2. To resend a packet through an interface to another interface, use the ip redirects interface configuration command.

There are the following command lines in the 1841 Router need to be modified:

interface FastEthernet0/1

ip address 192.168.0.81 255.255.255.0

ip access-group sdm_fastethernet0/1_in in

no ip redirects

no ip unreachables

no ip proxy-arp

ip nat outside

ip route-cache flow

duplex auto

speed auto

no mop enabled

After deleted these two lines: ip access-group sdm_fastethernet0/1_in in and no ip redirects, all computers are able to access both remote office and internet.

After the changes, the configuration looks like this:

interface FastEthernet0/1
ip address 192.168.0.81 255.255.255.0
no ip unreachables
no ip proxy-arp
ip nat outside
ip route-cache flow
duplex auto
speed auto
no mop enabled