PUBLIC IP FROM ISP

[muthanaalwaeli2050]

I have a problem with my core layer. I have given public IP address of 142.48.2.0/30 by the internet service provider(ISP) and the private address is 172.16.0.0/24. In the core layer, I have active and standby router which have been configured using HSRP. the problem is that the public address provides only two ip addresses and I do not know how to make the Two routers share the same Public IP address. 

[Karsten Iwen]

Ask your ISP for a /29 transfer-network. Without, you probably won't get any clean solution. Without that you could script something with EEM that monitors the router and reconfigures the IPs, but that's nothing that I would like to implement.

[muthanaalwaeli2050]

Actually, this is for an assignment and the tutor asked us to find any possible solution for this problem.

[hdecreis]

Hi,

if it's for an assignment, can you paste the exact problem description ?

(could be a /30 is available, you manage both the ISP and client-side, you could cut your /30 into two /31 for dual connectivity...)

Not enough information with what you posted.

Kind regards,

[muthanaalwaeli2050]

These two points are the requirements and the picture is just what I have done so far.

2.2 IP Addressing Requirements
An efficient IP addressing scheme is required using a Class B private IP address block for efficient use that caters to 30% growth of address requirements for the four departments. Sales department might experience significant growth (much more than 30%). As the public IP address (Internet) please use the 142.48.2.0/30. A DHCP server will be used for IP addresses allocation on the network.
2.3 Network Hardware
a) Switches in the building should provide for poor connectivity so that at if one switch fails a back up switch will provide an alternative path.
b) The WAN (Wide area network) cable from the Internet Service Provider’s hardware (DSL, cable modem etc) would be connected to the serial interface on the router.
c) A back up router should provide if primary router fails

[hdecreis]

muthanaalwaeli2050 said:

2.2 IP Addressing Requirements
[...]

As the public IP address (Internet) please use the 142.48.2.0/30. A DHCP server will be used for IP addresses allocation on the network.

[...]

b) The WAN (Wide area network) cable from the Internet Service Provider’s hardware (DSL, cable modem etc) would be connected to the serial interface on the router.
c) A back up router should provide if primary router fails

There is not enough information here. Or just wrong assumptions.

2.3.b) implies there is only one cable coming from the ISP. Using cable or DSL.

=> You have no control over the addressing there, it's usually just a /32 on PPP for DSL, or one IP in the middle of a wider /22-/24 for Cable (usually).

2.3.c) Given the topology described in 2.3.b) there is no redundancy possible on the ISP side, since one serial cable can be connected to only one router. You can only assume that the "backup router" is backup for the lan only, and just preconfigured for the ISP connection, so a user can manually unplug the ISP serial from the dead primary router to plug it on the backup one ...

=> This is ... correct for a home usage, at best (not mine), and a complete no-go in any kind of company.

Best of luck..

Kind regards,

[muthanaalwaeli2050]

Thanks a lot.