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Bridge Or Routing Mode on DSL Modem ???

Vikrant Ambhore
Level 1
Level 1

Hi All Friends,

In my office environment (less then 15 computers) with a Cisco 1861 Router & Business DSL, is it better to bridge the modem to the main router or leave the DSL modem in Router mode? & why?
Which Mode should be use, There is more option
1: Dynamic IP Address
     1483 Bridge IP LLC
     1483 Bridge IP VC-MUX
     1483 Routed IP LLC(Poa)
     1483 Routed IP VC-MUX

2:   Static IP address
      1483 Bridge IP LLC
     1483 Bridge IP VC-MUX
     1483 Routed IP LLC(Poa)
     1483 Routed IP VC-MUX

3:- PPPOe/PPPoA
     PPPoe IP LLC
     PPPoe Bridge IP VC-MUX
     PPPoa IP LLC
     PPPoa Bridge IP VC-MUX

4:- Bridge Mode
     1483 Bridge IP LLC
     1483 Bridge IP VC-MUX

I want  use dialer int of Cisco 1861 for getting IP from Modem ?  but I'm not sure if this modem can work as bridge just to translate packets to PPP from Cisco if this modem can work as bidge instead of router..
Can anyone suggest me  which protocol should be use for same ?
I ask because i have a BiPAC 5200S RC Series modem & it's been freezing a lot lately.  

My setup is BiPAC 5200S RC Series modem ----> Cisco 1861 Router -----> Switch



Regards
Vikrant

1 Accepted Solution

Accepted Solutions

Frederic Vanderbecq
Cisco Employee
Cisco Employee

Hello,

first of all, it all depends what you want to do and also the type of service you are getting from the service provider.

Using the bridge mode on the modem allows you to use another router (maybe with more features) to terminate the connection. Now, to be able to use the bridge mode, the modem needs to receive ethernet frames on the DSL/ATM interface, for instance PPPoE. If standard PPPoA is used by the provider, then bridge mode will not help you. In that case, you could connect the 1841 directly to the provider using a DSL or keep your current modem in routed mode.

If you are receiving ethernet frames from the provider (PPPoE for instance), then configure the modem in bridge mode and configure the 1841 with a dialer interface.

With regards to LLC or VC-MUX, it will again depend on what your service provider is using to encapsulate its frames in ATM: AAL5MUX (VC-MUX) or AAL5SNAP (LLC)

What is the current modem configuration (I guess it currently works in routed mode) ?

Fred

View solution in original post

1 Reply 1

Frederic Vanderbecq
Cisco Employee
Cisco Employee

Hello,

first of all, it all depends what you want to do and also the type of service you are getting from the service provider.

Using the bridge mode on the modem allows you to use another router (maybe with more features) to terminate the connection. Now, to be able to use the bridge mode, the modem needs to receive ethernet frames on the DSL/ATM interface, for instance PPPoE. If standard PPPoA is used by the provider, then bridge mode will not help you. In that case, you could connect the 1841 directly to the provider using a DSL or keep your current modem in routed mode.

If you are receiving ethernet frames from the provider (PPPoE for instance), then configure the modem in bridge mode and configure the 1841 with a dialer interface.

With regards to LLC or VC-MUX, it will again depend on what your service provider is using to encapsulate its frames in ATM: AAL5MUX (VC-MUX) or AAL5SNAP (LLC)

What is the current modem configuration (I guess it currently works in routed mode) ?

Fred

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