Equipment (Modems,Gateways)
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Comcast Cisco DPS 3939B with Cisco ASA 5505

Hi

We have received a Cisco DPS 3939B and some static IP's.

We want to migrate the ASA from the old non Comcast circuit to our new Comcast circuit, utilising one of the new static IP's.

 

The ASA will connect to the router and the LAN on the internal interface of the ASA.

The ASA will perform NAT and IPSEC L2L with another site.

 

There seems to be conflicting options on how to achieve this. Some say get the router converted to bridge mode and change the ASA so that it's external interface receives the public IP from Comcast.

 

What is the best/easiest way to get this working.

 

Thanks

 

SC

 

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Trusted Forum Contributor

Re: Comcast Cisco DPS 3939B with Cisco ASA 5505

Hello FFUSA and welcome,

 

You cannot use any Comcast or Industry standard modem in "True Bridge Mode (BM) " with static IPs due to the overall routing is totally disabled when in TBM. You can diable the DPC3939B internal DHCP Server so that your ASA's internal DCHP server will be used for your intre-network security and avoid any DHCP conflicts.

 

Therefore, you just need to program your ASA WAN with the required static IP routeable, gateway, and subnet mask addresses and this should be adequate. Also, your ASA internal firmware interface programming must be setup correctly for this.

 

Hope this helps you out.

View solution in original post

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Trusted Forum Contributor

Re: Comcast Cisco DPS 3939B with Cisco ASA 5505

Hello FFUSA and welcome,

 

You cannot use any Comcast or Industry standard modem in "True Bridge Mode (BM) " with static IPs due to the overall routing is totally disabled when in TBM. You can diable the DPC3939B internal DHCP Server so that your ASA's internal DCHP server will be used for your intre-network security and avoid any DHCP conflicts.

 

Therefore, you just need to program your ASA WAN with the required static IP routeable, gateway, and subnet mask addresses and this should be adequate. Also, your ASA internal firmware interface programming must be setup correctly for this.

 

Hope this helps you out.

View solution in original post

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