[New Office Setup] Routing between ASA Firewall and 1921 Router

[DaveU]

Hi All,

Good day, I need help on the new office setup involving routers and firewall. Please see below.

All public Ips here are changed. This is just an example.

OLD SETUP: I'm not sure why this is setup this way but Spectrum said that the 51.74.82.x network was a subset and was being forwarded out of the 25.40.117.x network. They use port number 3 on the spectrum modem. It is important to note that the 25.40.117.x only works on that port 3.

NEW SETUP: They have recently changed the public IPs assigned to them. Port 3 on spectrum modem will be deactivated which means the 25.40.117.x network will not be used anymore. They will be left with the new set of Public IPs. I don't think spectrum will replace the 25.30.117.x. network. Note that we are now using port 4 on spectrum modem.

Routing

[Georg Pauwen]

Hello,

in your drawing it looks like interface GigabitEthernet0/0 on the 1921 router has the same IP address as interface GigabitEthernet1/8 on the ASA ?

[DaveU]

Oh right, that's a typo. it should be 109.177.11.5. sorry bout that

[Georg Pauwen]

Hello,

that is still an invalid IP address,since you are already using the same address space on a different interface and a different device. Post the full configs of the ASA and the 1921.

[paul driver · Accepted solution]

Hello
On the cisco router you could to bridge its gig0/0 -gig0/1 interfaces using it ip address (109.117.11.x) then your ASA should be able to reach the spectrum

Cisco router
conf t

bridge irb
bridge 1 protocol ieee
bridge 1 route ip

int bvi 1
ip address 109.117.11.x 255.255.255.X

int gig0/0
description to spectrum modem
bridge-group 1

int gig0/1
description to ASA
bridge-group 1

[DaveU]

This worked! Thank you very much!

[Georg Pauwen]

On a side note, why do you need the router at all ? What else is the router doing ? You might as well connect the ASA and the Spectrum to the switch and have them communicate directly...

Maybe I am missing something here...