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Beginner

Configuring 1721 for transparent bridge mode

This is what I have to do and I'm a little confused.  I'm supposed to configure this 1721 for bridged mode, taking a Level 3 T1 into the serial 0 side and passing it out the f/e 0 side.  So, basically that's a T1 to ethernet conversion.  I guess this customer is buying a T1 from us but they have to use a different make/model router due to the large hospital requiring that of doctors offices.  I don't ask too many questions, I just do what I'm told.  Can this be done?

Encapsulation from Level 3 is ppp

static ip address, no password or anything like that.  Please provide the commands to make this happen.

Thanks!

1 ACCEPTED SOLUTION

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Dawn

You probably want an IP address on one interface but probably not on both. You do not need an IP address configured to make it work. But without an IP address on some interface then the only access you have to the 1721 is via its console port. So for access for monitoring and management you probably want an IP address.

If you follow my advice and turn off ip routing then you do not need the bridge irb command. You probably could get it to work using irb, but it would be much more complex and I do not see anything in what you have told us about your requirements that calls for irb.

If you are just bridging serial and Ethernet then why would you need NAT?

I do not understand your question about where the LAN side router points to.

Try this version of the link and see if it works better for you

http://www.cisco.com/en/US/tech/tk331/tk660/technologies_tech_note09186a0080094471.shtml#ex3

HTH

Rick

HTH

Rick

View solution in original post

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Hall of Fame Guru

Dawn

While I have not done this on a 1721 I have configured other Cisco router models to do transparent bridging between a serial interface and an Ethernet interface and I see no reason why it should not work on the 1721. There are several things that you need to do for this to work.

- first you need to turn off ip routing. use the command no ip routing

- then you enable bridging globally. I believe that the command syntax is bridge 1 protocol ieee

- then you enable bridging on the interfaces.

interface serial 0

bridge-group 1

interface fastethernet 0

bridge-group 1

- you can configure the ip address on either of the interfaces (but only on one interface)

You can look at this link for additional details

http://www.cisco.com/en/US/partner/tech/tk331/tk660/technologies_tech_note09186a0080094471.shtml#ex3

HTH

Rick

HTH

Rick
Highlighted

Do i need an ip address on either interface?

That link you posted doesn't work

Do I need the bridge irb command?

Do I need any NAT commands?  And where does the LAN side router point to? 

Highlighted

Dawn

You probably want an IP address on one interface but probably not on both. You do not need an IP address configured to make it work. But without an IP address on some interface then the only access you have to the 1721 is via its console port. So for access for monitoring and management you probably want an IP address.

If you follow my advice and turn off ip routing then you do not need the bridge irb command. You probably could get it to work using irb, but it would be much more complex and I do not see anything in what you have told us about your requirements that calls for irb.

If you are just bridging serial and Ethernet then why would you need NAT?

I do not understand your question about where the LAN side router points to.

Try this version of the link and see if it works better for you

http://www.cisco.com/en/US/tech/tk331/tk660/technologies_tech_note09186a0080094471.shtml#ex3

HTH

Rick

HTH

Rick

View solution in original post