ISP BGP Dual-Home

[acostram1500]

Hello everyone I hope someone can give some feedback on my question.

We are building a new site and also getting two Internet circuits for the site. The setup is going to be Dual-homed Active/Active using the same ISP. We also have blocks of /24 public IPs from our ISP.

My question is can we segment the blocks of IPs that are given  by our ISP into smaller subnet? Or what would be the logical or optimal way of implementing this design with these blocks of public IPs? I included the diagram in this post as well.

Thank you all in advance.

RAM

Attachment: 

diagram.png

[pdub206]

Yes you can segment them into smaller subnets.  All your ISP needs from you is the networks advertised back to them.  If you have two /24's in a row you could even advertise a /23 back to them.  Note that most ISP's will not accept anything smaller than a /24.

I would set up dynamic routing between your edge routers and firewalls, then have your firewalls advertise the /24 networks outbound.  Your edge routers can then redistribute them into BGP for advertisement to the rest of the internet.

[acostram1500]

Thanks Patrick,

Just want to clarify when you said advertise back to ISP your referring to the public IP blocks that that are given to us by our ISP right?

Thanks,

RAM

[pdub206 · Accepted solution]

Correct.  You can do this with the network command under router bgp <as number>, or you can do it by redistributing networks into BGP (static or dynamic).