Adding an additional Public IP Block on my Cisco 2801 Router

denver218
denver218 used Ask the Experts™
on
I have a Cisco 2801 Router that connects me to the ISP.  This Router also does NAT/PAT, Firewall, VPN, etc.

As you can see below by looking at my interface configurations, I only have a /30 block of IP addresses.  We are getting an application on one of our servers that require a static NAT.  Since I don't have any IP addresses, my ISP just assigned me an additional block of IP's which is a /29 block.  So I have my WAN connection, which is a /30 block, and I have my public rout-able IP block which is a /29 block.  How do I configure my router for this additional IP Block?  Behind my 2801 router its a cisco 2950 switch.  The router is connected to the switch via interface FastEthernet0/0.  Should I add a secondary IP from the /29 block to interface FastEthernet0/3/0.1?  See interface configurations below:  Any assistance would be greatly appreciated.

interface FastEthernet0/3/0
 no ip address
 duplex auto
 speed auto
!
interface FastEthernet0/3/0.1
 description WAN_ISP
 encapsulation dot1Q 10
 ip address x.x.205.6 255.255.255.252
 ip nat outside
 no cdp enable
!
interface FastEthernet0/0
 description TO CISCO 2950 SWITCH LAN
 ip address 172.17.0.1 255.255.0.0
 ip nat inside
 ip virtual-reassembly
 speed auto
 full-duplex
 no cdp enable
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Top Expert 2012
Commented:
Add all the IP addresses of your block as /32 secondaries to your interface FastEthernet0/3/0.1:

interface FastEthernet0/3/0.1
 description WAN_ISP
 encapsulation dot1Q 10
 ip address x.x.x.9 255.255.255.255 secondary
 ip address x.x.x.10 255.255.255.255 secondary
 ip address x.x.x.11 255.255.255.255 secondary
 ip address x.x.x.12 255.255.255.255 secondary
 ip address x.x.x.13 255.255.255.255 secondary
 ip address x.x.x.14 255.255.255.255 secondary
 ip address x.x.205.6 255.255.255.252
 ip nat outside
 no cdp enable

Author

Commented:
Thanks.  I only had to add one IP Address in the block as a secondary.  For the network devices that required a Static NAT, I just entered the Static NAT and all worked fine.  Thanks.

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