Not able to access/ ping machine behind router without adding router IP in LAN interface

There are 3 points in 3 city connected through MPLS network.

Installed 3 Cisco 878 Modem-Router in each location.

The problem is:

When you want to ping (access) a computer behind any of these routers you MUST add your router’s IP address in gateway of LAN cards.

If don’t, you can not access it anyway! This issue caused a lot of problem on ISA machine. (Multi gateway)

You may see a test trace route below (from our router to a pc behind another router) and also a copy of router’s show run.

Router1#traceroute 192.168.20.10

Type escape sequence to abort.
Tracing the route to 192.168.20.10

1 172.17.7.61 24 msec 24 msec 28 msec
2 217.218.188.25 36 msec 36 msec 36 msec
3 217.218.185.18 36 msec 36 msec 36 msec
4 * * *
5 172.17.6.126 36 msec 32 msec 32 msec
6 192.168.20.10 36 msec 32 msec 36 msec
As you can see in trace route, the packet does not go through my Vlan1 IP address, it goes through the IP of my ATM0.

Current configuration : 1198 bytes
!
version 12.4
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Router1
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
!
dot11 syslog
ip cef
!
!
ip name-server 192.168.10.15
!
!
!
username admin privilege 15 secret 5 ***EDITED***
!
!
archive
log config
hidekeys
!
!
controller DSL 0
mode atm
line-term cpe
line-mode 2-wire line-zero
dsl-mode shdsl symmetric annex B
line-rate auto
!
!
!
!
interface BRI0
no ip address
encapsulation hdlc
shutdown
!
interface ATM0
ip address 172.17.7.62 255.255.255.252
no atm ilmi-keepalive
pvc 0/35
encapsulation aal5snap
!
!
interface FastEthernet0
!
interface FastEthernet1
!
interface FastEthernet2
!
interface FastEthernet3
!
interface Vlan1
ip address 192.168.10.1 255.255.255.0
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 172.17.7.61
!
no ip http server
no ip http secure-server
!
!
!
!
control-plane
!
!
line con 0
login local
no modem enable
line aux 0
line vty 0 4
privilege level 15
login local
transport input telnet ssh
!
scheduler max-task-time 5000
end

It's just a layer 3 configuration for our end point routers. Problem raise when you do not enter gateway ip address in LAN of clients.

Soution:

This is happening because MPLS network is not properly configured so talk to your mpls provider and get it properly configured because layer 3 is the end points which talks to the layer 2.5 label routers. only gateway you should need is your local one. clearly the mpls network isn't routing correctly and you can't correct this at layer 3.

You should not have to add a static route at the PC level. All you need a default route to your ISP and the routing to your network (internal) should not be a problem.

Adding a static route is a band aid fix and can you add a static route for 50 machines if you had too? Too much administration.

You should really check this with your ISP.