Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

Loopback address design questions

First, picture a pair of Cat6509's, attached to a pair of Cat3560's... connecting over a telco TLS circuit to a remote site.  At the remote site is another pair of 3560's, then a pair of ASA's, and one more pair of 3560's.

I've been asked to put loopback addy's on every device, which, oddly enough, has never been requested of me before.  I have a question about where to snag the IP's from in the range provided.

IE, I've been given the 10.5.64.0/24 range to IP all of these mini subnets.

So, if I use the 10.5.64.0 /29 for the pair of 6509's (having 64.1 and .2 as the HSRP vips) and the 3560's (having IP's of 64.3 and .4 respectively), then now I have to add loopbacks to the same four devices.

My gut says to take the next four /32's of 64.9 for the first 6509, and 64.10 for the second... and 64.11 and 64.12 for the 3560's.

Then I can begin my next /29 using 10.5.64.16.

Am I missing anything obvious?  Is there an easier way to separate out one IP address at a time for the purpose of loopbacks

Thanks,
mike

Everyone's tags (3)
1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: Loopback address design questions

Hello Mike,

usually is better to pick up loopback addresses from a dedicated block or sub-block

in your case you can pick up /32 loopbacks starting from 10.5.64.224/27

for clarity I would not mix between loopback addresses and IP subnets used at each site.

You can build a table with your loopback choices for documentation purposes

loopback addresses are also used as OSPF router-id or for other routing protocols so it is handy to use the highest sub-block for them, because it remembers that are used for this.

This is just my opinion and how I usually assign loopbacks.

Using /29 at the sites may be too small as it doesn't leave space for additional devices (2 C6500 1 VIP HSRP and 2 C3560 and there is only 1  free address left with /29) that  may be added in the near future I would use a /28 subnet mask in each site.

Hope to help

Giuseppe

2 REPLIES
Hall of Fame Super Silver

Re: Loopback address design questions

Hello Mike,

usually is better to pick up loopback addresses from a dedicated block or sub-block

in your case you can pick up /32 loopbacks starting from 10.5.64.224/27

for clarity I would not mix between loopback addresses and IP subnets used at each site.

You can build a table with your loopback choices for documentation purposes

loopback addresses are also used as OSPF router-id or for other routing protocols so it is handy to use the highest sub-block for them, because it remembers that are used for this.

This is just my opinion and how I usually assign loopbacks.

Using /29 at the sites may be too small as it doesn't leave space for additional devices (2 C6500 1 VIP HSRP and 2 C3560 and there is only 1  free address left with /29) that  may be added in the near future I would use a /28 subnet mask in each site.

Hope to help

Giuseppe

New Member

Loopback address design questions

it's correct

in this mode you not lose the "network" and "broadcast" address but at the same time you don't overlap nothing

regards

665
Views
0
Helpful
2
Replies