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True Bridge Mode on DPC3939B for comcast business

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bstr
New Member

True Bridge Mode on DPC3939B for comcast business

I have a newly installed 150MBit comcast business service with 5 static IPs which came with a DPC3939B router.

 

We are having problems with the device changing TCP options on our traffic and need to get the device into true bridge mode.  I contact support and was told that the DPC3939B did not have a true bridge mode and was offered a pseudo-bridge mode.

 

Because we do protocol development we need actual internet connectivity which is free from manipulation of intermediate header rewriting, pseudo bridge mode isn't going to work-- we'll need true bridge mode. Right now the service is not usable for us.

 

I don't mind going out and purchasing another modem-- and SB6183 appears compatible with the 150MBit service, but I was previously told that I would need to use a comcast modem to get static IPs routed to me.

 

What do I need to do to get my connectivity without the device modifying my packets while preserving access to my static IPs?

 

Trusted Forum Contributor

Re: True Bridge Mode on DPC3939B for comcast business

unfortunately, there's not much you can do. Static IPs cannot be provisioned to customer owned modems; you must lease a Comcast gateway for that. As far as I've known, the gateways should do no modifying of traffic to/from static IP assigned devices.As for header "re-writing", I know that Comcast uses RIP authentication/encapsulation for static IP traffic on their coax network, so you MIGHT be seeing the effects of that...

 

Are you using your own router behind the DPC? Typically that is the recommended config - assign the WAN port of your router with the Comcast-provided static IP information. As a last resort, you can ask to have the Cisco swapped out for another model of gateway (currently gateways are available from Cisco, Netgear, and SMC, though which devices your area/market provides will vary.)

bstr
New Member

Re: True Bridge Mode on DPC3939B for comcast business

> Are you using your own router behind the DPC?

 

Thats my intention eventually; though right now I've been testing with a host directly on the static IP.

 

> Static IPs cannot be provisioned to customer owned modems; you must lease a Comcast gateway for that.

 

I don't have a require to use our own modem vs comcast's except that customer support said that the comcast 3939B could not be placed in a true bridge mode where it wouldn't modify the traffic.  I hear from residential users with apparently the same hardware (and see other posts) in this forum which suggest otherwise-- I just need to know how to go forward.

 

 

 If we have to get rid of the static IPs to make the service usable for us then we're willing to do that.

Trusted Forum Contributor

Re: True Bridge Mode on DPC3939B for comcast business

What the rep said was right. Putting a gateway into bridge mode removes all static IP configuration. As long as youre ok with getting rid of statics, give bridge mode a try. If that fails, try swapping out with a retail unit. I am currently running an SB6183 with no noticed issues.