877 bgridge config

Answered Question

Hi,

I am facing some problem to configure 877 router as a bridge mode. In my network scenario (LAN ip: 192.168.0.0/24) -----1841(ip 119.75.14.145) ------877------ (ATM0.1) ---Internet

Here i have attached the 877 router config. I can't ping the isp router from 1841 router.

Please let me know if i missing some configuration on 877 router.

I am confident that 1841 router configuration is ok.

Regards,

Mamun

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Correct Answer by patrickvanham about 8 years 1 month ago

In your scenario, the 877 is effectively used as a modem in bridging mode, and I'd advise using a standard modem the ISP normally supplies. If you want to use the 877 you need to link the internal interfaces connected to the 1841 with the external interface. This is done via a BVI.

In order to do the NAT on the 1841 you'd need to route traffic on the 877, but you'd have to have a public IP address on the 877 in the same range as on the 1841.

Another way would be to add the correct WIC to the 1841 and connect that directly to the internet, bypassing the 877 altogether.

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Giuseppe Larosa Sun, 10/26/2008 - 04:32

Hello Mamun,

you need IRB complete config

add the following:

bridge 1 route ip

bridge 1 bridge ip

interface BVi1

ip address 119.75.14.145

BVi1 is the logical L3 interface associated to bridge-group 1

Hope to help

Giuseppe

Hi Giuseppe,

Thanks for reply. The ip address that you have mentioned for BVi interface I already used in fa0/1 interface in 1841 router & Fa0/0 is used 192.168.0.3/24

Does it mandatory to configure Bvi interface if we don't need to remote management?

Have any problem in ATM0.1 sub interface for bridge mode? Can we configure ATM0 for the same?

If possible please let me know.

Regards,

Mamun

Giuseppe Larosa Sun, 10/26/2008 - 06:03

Hello Mamun,

you weren't able to ping the ISP because f0/1 is a separate broadcast domain.

BVI is needed to be able to exit from the bridge-group with a routing action.

So with a BVI you can access internet also from f0/1.

By the way in your post there is no evidence of the routed ports so I tried to guess what was missing.

by bridging over ATM you have a single broadcast domain with your ISP: if they provide you a DHCP service end users in vlan1 can access the internet.

Of course you are free to implement the Internet access as you like

Hope to help

Giuseppe

Correct Answer
patrickvanham Tue, 10/28/2008 - 03:29

In your scenario, the 877 is effectively used as a modem in bridging mode, and I'd advise using a standard modem the ISP normally supplies. If you want to use the 877 you need to link the internal interfaces connected to the 1841 with the external interface. This is done via a BVI.

In order to do the NAT on the 1841 you'd need to route traffic on the 877, but you'd have to have a public IP address on the 877 in the same range as on the 1841.

Another way would be to add the correct WIC to the 1841 and connect that directly to the internet, bypassing the 877 altogether.

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