Routing issue ( problably newbie quest )

[boymarty24]

Hello!

I am a new to routing and cisco, a real beginner...I have ha problem, probebly easy solved by an experienced person.

My problem is the following. I have 2 offices connected together with a cisco routers. I want both offices to have the same subnet ( 192.168.1.0 255.255.255.0 ). The are connected with a serialline. I have tried to configure the routers but have not been succesful. I can ping the interfaces but not the computers on the lan.

Is there anything I need to consider when configuring the routers. If you want I can post my cfg...

Would be really happy if anyone could assist me

//M

 

[CCIEcandidate]

Go ahead and post your configs.

 

[Patryn]

This is not possible M. because a directly connected interface will never be routed.
See when you have a host in the 192.168.1.0 who tries to communicate with anouther host in the 192.168.1.0 he will for one never use his default gateway hense never get to the router and two even when he would deliver his package to the router the router would see the 192.168.1.0 as a directly connected interface and not route but preform an arp request.....on the subnet where the packet came from on the first place.

One way of solving this is breaking your subnet up in two pieces.
Like 192.168.1.0 /25 and 192.168.1.128 /25
But the serial connection between the routers needs to be a different subnet too.
Or depending on your serial link you might get there with bridging, but I wouldn't recommand that.

 

[NetEng631]

Try bridging. Not sure if you can do it on your version of the router. You will need to look on cisco's web page. If you can do a bridge will work.

 

[NetEng631]

Forget the briding suggestion. You can only bridge Token ring on a router. But a bridge would work.

You can subnet the network into two /25's and have each network on either side of the T1. You can use a /30 or IP unnumber on the T1 Link

 

[boymarty24]

That was what I thought, maybe you here can help me to solve the problem.
The person who did this doesn´t work here any more. The two offices, main and remote are connected with a serialline. Problem is that i need to access a server on the remote office from the main office.

Something todo with the nat configuration a assume. Access from remote to main works fine. Is there a way to do a open a route so that main office can access the lan on remote site.

This is problably easy, but for a dumb projectmanager...

here are the configs...

main:


interface FastEthernet0/0
ip address 192.168.1.2 255.255.255.0
no ip mroute-cache
speed auto
full-duplex
!
interface Serial0/0
ip unnumbered FastEthernet0/0
no ip mroute-cache
!
interface Serial0/1
ip unnumbered FastEthernet0/0
no ip mroute-cache
shutdown
!
!
ip classless
ip route 0.0.0.0 0.0.0.0 192.168.1.1
ip route 192.168.1.3 255.255.255.255 Serial0/0
ip http server
ip pim bidir-enable
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4

remote

interface FastEthernet0/0
ip address 192.168.0.1 255.255.255.0
ip nat inside
ip route-cache same-interface
no ip mroute-cache
speed auto
half-duplex
!
interface Serial0/0
ip address 192.168.1.3 255.255.255.0
ip nat outside
no ip mroute-cache
no fair-queue
!
interface Serial0/1
no ip address
no ip mroute-cache
shutdown
!
!
ip nat log translations syslog
ip nat inside source list 7 interface Serial0/0 overload
ip classless
ip route profile
no ip route 0.0.0.0 0.0.0.0 192.168.1.1
no ip route 192.168.1.2 255.255.255.255 Serial0/0
ip http server
ip pim bidir-enable
!
access-list 7 permit 192.168.0.0 0.0.0.255
!
line con 0
line aux 0
line vty 0 4

 

[Patryn]

Man this is one of the ugliest configs I've ever seen.
No offense.

Anyway, when you only need to access one server on the remote location, you could use a static nat entry, but this either works for only one host on the inside or for multiple host but only for specific services (like http or smtp or dns etc) based on port number.

ip nat outside source static 192.168.1.3 192.168.0.x where x is the host you're trying to connect to.

But a total redesign would be advicable....

Regards,

Pat

 

[robertjo24]

No offence to Patryn, but depending on the router and IOS, you can bridge serial interfaces. We have been doing it for years between two facilities connected with dedicated T1’s. What you want to do can be accomplished with bridge groups.

 

[PinkLips]

You can bridge using a "Dexter" which handles 4 T1s over fiber. This will also allow you to keep the same subnet without having to break it into /25. However, remember that this just increases the number of "points of failure" during troubleshooting.


Thanks,
Nicole