Solved: Layer 3 point to point links

cowetacoit · ‎09-02-2008

I have a design question. I am in the middle of restructuring our network using a routed access layer design. I am using a 10.0.0.0 /16 for each building i have, then a /24 for individual vlans within that building and advertising a /8 to my core. This is kind of a basic question i should probably know, but what is the best structure and practice for point to point routed links? Should they be in the same subnet as my /16 that i advertise to the distribution block or should i just use an entirely different IP with a /30?

For example, I have a building called "Building 5". It's summarized subnet would be 10.5.0.0 /16. I have a few vlans such as vlan 100 (10.5.100.0) and vlan 200 (10.5.200.0) Could my P2P links be 10.5.1.1 and on the distribution be 10.0.5.1.2 /30? or should i use something completely differentlike 192.168.1.0 /30?

Collin Clark · ‎09-02-2008

Mine is still in the 10 network (along with server and client subnets), but it's way outside the normal ranges. I like to start at the high end and work my way down. For example my first subnets would be-

10.255.255.0 /30

10.255.255.4 /30

10.255.255.8 /30

...

Different classes would be effective too.

View solution in original post

Collin Clark · ‎09-02-2008

I use a separate address space with /30 masks. When you traceroute, it's easy to spot "transit" links.

Hope that helps.

cowetacoit · ‎09-02-2008

I just edited my message....

So you think a probably a 192 or 172 private address would be easier to spot? I see your point.

Collin Clark · ‎09-02-2008

Mine is still in the 10 network (along with server and client subnets), but it's way outside the normal ranges. I like to start at the high end and work my way down. For example my first subnets would be-

10.255.255.0 /30

10.255.255.4 /30

10.255.255.8 /30

...

Different classes would be effective too.

cowetacoit · ‎09-02-2008

I like your design better than using a different class. Thanks for clearing that up.

stinderella · ‎10-08-2019

how do you configure at interface level?

Joseph W. Doherty · ‎10-08-2019

If I'm working with summary prefixes, I try to assign all IPs out of the same block.

To identify loopbacks or p2p IPs, I usually assign from a specifiic /22, /23 or /24 from the /16. For example loopbacks might all be from 10.x.0.x and p2p from 10.x.254.x, etc.

BTW, depending on your routing protocol, you might use /31s for p2p.