Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

IP address assignment question

I've got the following network topology:

ISP>Cisco 1841>Secureworks IDS Box>Checkpoint Firewall>Internal router

I have one subnet assigned to my network. I needed a few IP addresses so I could install another network device from Bomgar. Unfortunately my ISP couldn't give me more IP addresses on the same subnet so they gave me a new /29 addressing scheme to use.

My question is do I need to assign an external static IP to each of the devices in the chain in order to get them to communicate?



New Member

Re: IP address assignment question

Hi Hugh,

See the attachment it might help.




Re: IP address assignment question

First question...why do you have 2 routers in this topology? Basically, why do you have an internal router after the Firewall? now have 2 /29 blocks not together? There are a few ways to do this but it is based on requirement. You could just add the subnet to the primary interface as a secondary ip address, then assign that block to the devices and the default gateway will be the IP address you assigned to the primary interface for the devices on the network.

For example:

FastEthernet 0/0

ip address

ip address secondary

This interface is now the default gateway for both networks.

does that make sense?

Need just a little more info so we can make sure we give you the correct info.

New Member

Re: IP address assignment question

Thanks much, that makes sense now. It turns out that the router behind the firewall is where 4 point to point T1s terminate for satellite locations.

So if I assign an IP address from the new subnet to the internet facing router that will make it able to route traffic for that subnet. Sounds like all I would need at that point would be one more static IP so that the bomgar remote control device is accessible from the internet.

There is an open WIC slot in the 1841, I was thinking I could put in another FastEthernet WIC in there, assign one of the new subnet IPs to that then connect that directly to the bomgar. Assign one more IP to the bomgar and the bomgar to the local network switch and all should be good. Sound OK?

Thanks so much for the assistance.



Re: IP address assignment question

It sounds like you are on the right track for set-up. Basically what you need to keep in mind is if you want a seperate network/subnet then you need to assign it somewhere. If you have different interfaces then you can have that, or you could use sub-interfaces too. Or as said before a secondary IP. You cannot have the same subnet on any other interface.

CreatePlease login to create content