Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

Switch from Bridge to Route

I have a number of locations throughout the country connected together over frame relay, all of which are bridged. (Cisco 1601s) I would like to route these now instead of bridge them. I know how to set up all the routing, but wondered if anyone had any ideas about the process of doing this without losing my remote connection in the process. Is it possible to set up the routing first and then turn off bridging? I do not have access to these routers through out-of-band means. The best I can do remotely is have someone turn the router off and on again if I screw up.

Any suggestions will be appreciated.



Re: Switch from Bridge to Route

There so many things to be taken care when you are switching to routing. So just keepin mind difference between frame relay bridging , spilt horizon, arps . just go through this link

You can utilise another feature called Autoinstall over frame-relay desccribed here

Re: Switch from Bridge to Route

Hi Chris,

I was in the same trouble two years ago.

My steps were following:

1) Prepare new IP addressing plan. You need to change your IP addressing scheme completely - the easiest way is to leave the current addressing in the central site and change addresses per one location.

2) Configure Integrated Routing and Bridging (IRB) or Concurrent Routing and Bridging (CRB) on the central router (I suppose a star network topology).

This enables you start routing to one location and leave bridging on the others in the first step. If everything works OK, you can continue with another location.

3) Prepare a new (routed) config for a remote location router. The easiest way is to load it to the remote router startup config, reload the remote router, change the config on the central router to route the remote side and hope everything works OK.

If not, it's necessary to ask someone to load the original config to the remote router (and reload it) and change the central router config back. (This was my way, I had a technician staff on the remote side. I onle used temporary passwords in the new config not to have to say them the production password in the case of trouble.)

If there is nobody able to load the origin config back to the router on the remote side, your situation is much more difficult. I can imagine preparing a config file (script) reflecting all necessary changes in the running config to move from bridging to routing. I.e. some "no ...." commands to remove bridging, adding IP addresses to proper interfaces, etc.

You could copy such a file to a remote router flash and issue a "copy flash run" command to merge the current running config with this file. In a case of trouble you could just ask someone to power off/on the remote router (the startup config remained unchanged).

But if your remote routers are old (Flash running) 1601s, it's impossible to copy a file to the flash. So you might copy the file to a tftp server on the remote site and issue "copy tftp run" command. (You could also configure the remote router to use startup config from a tftp server and copy a complete new config to the tftp server.) But using a tftp server on the remote site makes the procedure even more complicated.

4) After changing config to routing on the remote site check that everything works OK. Change the IP addresses of all PCs on the remote site. Leave the location to work some time (one week at least) to be sure all applications are working in the routing environment with no problem.

5) Continue with another site.



New Member

Re: Switch from Bridge to Route

Thank you for your thorough explanation. You confirmed for me what I feared....there seems to be no easy way. I have a few extra routers identical to the production ones. Do you know of a way I can set up a mock frame-relay test environment with two routers back to back? If so, could I then configure the production main router as you described in step two and send the flash card to the site, have them plug it in and turn it on? Then they could send the old one back and I could use it to configure the next location.

Your ideas are very appreciated here.


Re: Switch from Bridge to Route

This link shows you how to simulate a FR with two routers back to back



Re: Switch from Bridge to Route

Well, if you have some spare identical routers, your sitution is much better.

You can send a Flash or a complete router preconfigured to the remote site and ask someone simply replace the router. If anything fails, just swap the routers back and return to bridging again.

Good luck,


New Member

Re: Switch from Bridge to Route

As a side note.

The command that has saved my butt several times is the 'reload in x'

Anytime I am remotely working on a router and I have the slightest fear of getting kicked out, I will run that command and do all my changes without doing a wri mem, if all goes well then you can cancel the reload, or if you need more time then redo the command for as many minutes as you need.

That way I can do the work afterhours without any one staying late waiting around.

It has saved me many late night drives.

New Member

Re: Switch from Bridge to Route

Ahh. Thanks for the tip! That seems very useful.

Re: Switch from Bridge to Route

You could potentially create a "script" and tftp it into the "running config" that would simulate changing the config. Using that instead of tftp'ing it into the "startup config" allows you to then use the "reload in X" command that someone else mentioned here.

One >very< useful thing to use when doing this, and your IOS has to be at a certain level for it to work, is the "default interface XXX" command. ie: If you want to take your serial interface, which is configured for bridging, and reset it back to factory defaults in your script, you could simply do a "default int" on it, then configure the interface as usual... Example:

default interface Serial0/0

interface Serial0/0

ip address ....

This makes it easier than having to do a "no XXX" for each line you want out of the "old" config.

Good luck and be careful!! Remember that if it doesn't work the first time, your reload will set it back in a few minutes. Also, don't just wait for the reboot, try using "cdp neigh detail" and any other means to get debugging while its down to help you figure out what went wrong!!