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New Member

How should I subnet a 150 site WAN? ip addressing / network addressing

we are upgrading our WAN. It will be comprised of approximately 150 sites and 2 "home" or "hub" sites. The transport technology will be FRAME RELAY with INTERNET VPN (or ISDN) for backup and low-priority traffic. The topology is basically each site having connectivity to two "HOME" locations where all their main resources will be located. I am looking for advice or white papers and case studies on the best way to layout an IP ADDRESSING scheme that helps avoid problems in the future.

6 REPLIES
Cisco Employee

Re: How should I subnet a 150 site WAN? ip addressing / network

Here is the link for internetwork design guide for all the technologies.

http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/

It does have a link for "Appendix A: Subnetting an IP Address Space"

New Member

Re: How should I subnet a 150 site WAN? ip addressing / network

thanks. is there any more available for case study?

by the way. who can i complain to in your product department?? your new equipment is shipping with console cables that have the 9pin connection molded into place. The old flat cables were better for remote troubleshooting because one could have somebody connect from the aux port of a router to the console port of another device.

Silver

Re: How should I subnet a 150 site WAN? ip addressing / network

Appropriate addressing schemes will depend upon a number of factors, including the routing protocol in use, the address space available to work with, expectations of future growth, and even the tool available for troubleshooting. For example, in my book, I discuss an addressing scheme used in a several hundred site hub and spokes network using EIGRP and unlimited address space (RFC1918). In a meshed OSPF network, the scheme would be a disaster because it is not designed to facilitate address aggregation. Ditto if using "real" IP addresses where every available IP must be used in every subnet.

FWIW: Many issues unique to a hub and spoke network, including use of ISDN backup and multiple hub sites are covered in Chapter 7 of my book "High Availability Networking with Cisco." Just be forewarned that it is not your typical network design book... I made the mistake of assuming the reader already understood fundamental network design and routing issues, and skip right over the basics to go to the hard core issues in high availability on a low budget.

Good luck and have fun!

Vincent C Jones

www.networkingunlimited.com

New Member

Re: How should I subnet a 150 site WAN? ip addressing / network

my current network is single-hub and about 120 frame remotes with ISDN dial backup and EIGRP. The new network will be 2 hubs (all remotes planned for connection to both hubs) and also running EIGRP. Within the company I work for I have been allocated the 172.20.x.x and 172.30.x.x private spaces.Each remote is planned for initially consuming a class C but with the provision for slipping a bit in the mask and going to 512. Frame will be primary with either DSL/vpn or ISDN as a backup or traffic offloading method.

your book sounds like it could save me a lot of time since my envionment sounds very similar to what you have already illustrated. I'll look to buy it today.

New Member

Re: How should I subnet a 150 site WAN? ip addressing / network

I ordered the book on Thurs. It hasn't arrived yet, but I have a question. How do you recommend dealing with loopback addresses? Would there be any problem having the loopbacks be from a different private network .. say 10.x.x.x rather than the 172.x.x.x network that would be used for the rest of the WAN? It would make troubleshooting a little easier from the "human" point of view since any reference to a "10" address would point to a loopback rather than a physical interface.

Silver

Re: How should I subnet a 150 site WAN? ip addressing / network

No problem putting loopbacks elsewhere, they are advertised as /32 host routes whereever they are. The trick is allocating all the addresses needed so that they can be easily summarized if the network expands to thousands of spokes. My preference is to use "human" oriented addresses, but they tend to be wasteful of address space, so tend to be limited to RFC1913 address space.

Good luck, have fun, and enjoy your reading :-)

Vincent C Jones

www.networkingunlimited.com

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