Anilrgowda

I have a Cisco 1721 router with a single WIC t1 card. The wic card plugs into the smart jack to the ISP and the fastethernet plugs into a Sonic Wall that handles all my lan work.

The following configuration does not work. If I remove the fastethernet IP address (no ip address YY.YY.255.113), I can telnet from outside into the router and ping yahoo with success. But if I enter the YY.YY.255.113 ip into the fastethernet0 I cannot see the router from the outside or inside. If I type “show ip route” I get default gateway is not set but unsure if this matters or is correct. I am also not sure if the gateway they gave me is correct, XX.XX.140.173 or should it be YY.YY.255.113?

The ISP gave me :
CSU information
Clock source: line
Channels: 1-24
Framing: esf
Line coding: B8ZS

Router info:

T1 serial as follows:
Encapsulation: PPP
T1 serial/WAN interface
Serial or wan IP: XX.XX.140.174
Subnet mask: 255.255.255.252

LAN IP address
Lan ip address: YY.YY.255.113
Subnet mask: 255.255.255.252
Gateway or remote ip: XX.XX.140.173 (I think)


XXXXXXXXXXX#show running-config
Building configuration...

Current configuration : 1192 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname XXXXXXXXX
!
enable secret 5 XXXXXXXXX
enable password XXXXXXXX
!
ip subnet-zero
no ip routing
!
!
ip domain name cavtel.net
ip name-server 64.83.0.10
ip name-server 209.137.160.3
!
!
!
!
!
interface FastEthernet0
description To Office
ip address YY.YY.255.113 255.255.255.248
no ip route-cache
speed auto
full-duplex
!
interface Serial0
description To ISP
bandwidth 1536
ip address XX.XX.140.174 255.255.255.252
encapsulation ppp
no ip route-cache
no fair-queue
service-module t1 timeslots 1-24
!
ip classless
ip route 0.0.0.0 0.0.0.0 XX.XX.140.173
no ip http server
!
snmp-server community 6f72fb15ad RO
snmp-server community public RO
snmp-server enable traps snmp authentication
snmp-server enable traps tty
!
line con 0
password XXXX
login
transport preferred none
line aux 0
password XXXX
login
modem InOut
transport preferred none
transport input all
transport output pad udptn telnet rlogin
stopbits 1
flowcontrol hardware
line vty 0 4
password XXXX
login
transport preferred none

Anilrgowda

Damn. I didn't see the "no ip routing" in the config that you posted either. With it normally being enabled by default, I don't always look for it.

I would use the 2nd option with IP address on the serial interface.
It is preferable to use the IP address of the next hop as the default gateway.