An ability to get a parent prefix from an ip address using API

[zelfix]

Issue type

[X] Feature request
[ ] Bug report
[ ] Documentation

Environment

• Python version: 3.4.5
• NetBox version: 2.2.6

Description

It is a continuation of NetBox-discussion https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/netbox-discuss/t7J_LL2jMcM/dOvZVqEYAQAJ
Would like to get the closest parent prefix for an IP address using API.

It would be useful for those that use a netbox with external tools. For example, I want to add a list of ip addresses to netbox from a core switch's arp table using API. For each ip address I must set a prefix length. If I could get a parent prefix using API than I could get a prefix length for this IP address.

[Gunni]

If you have the ip with mask on CIDR form, just do the following request:

/api/ipam/prefixes/?parent=10.0.0.1%2F24

In my test it returns the parent prefix of 10.0.0.0/24.

Edit: Just noticed that you said you didn't have the prefix length. But you do, if you have ARP then you have a layer 3 interface and that interface has a mask set, right?

[zelfix]

Yep, If I have the ip with mask, i can calculate the prefix and get it using API
But If I don't know a mask, I have to do something like this:

def get_prefix_length_for_ip(ip_address):
    for prefix_length in range(31, 0, -1):
        resp = requests.get(apiBaseUrl + '/ipam/prefixes/?parent=' + ip_address + '/' + str(prefix_length),
                            headers=headers).json()
        if resp['count'] > 0:
            return str(prefix_length)
    return None

This code gives a big load to the Netbox database that's why the function is executing slowly.

[Gunni]

Just noticed that you said you didn't have the prefix length. But you do if you have ARP then you have a layer 3 interface and that interface has a mask set, right?

Example from an IOS XR router:

# show int Bundle-Ether1.XXX
Bundle-Ether1.XXX is up, line protocol is up
...
  Internet address is XX.XX.XXX.29/28
...
# show ipv4 vrf all int brief | i Bundle-Ether1.XXX
Bundle-Ether1.XXX              XX.XX.XXX.29    Up              Up       example-vrfname
# show arp vrf example-vrfname Bundle-Ether1.XXX location 0/0/CPU0
Address         Age        Hardware Addr   State      Type  Interface
XX.XX.XXX.17    00:42:23   XXXX.XXXX.XXXX  Dynamic    ARPA  Bundle-Ether1.XXX
XX.XX.XXX.29    -          XXXX.XXXX.XXXX  Interface  ARPA  Bundle-Ether1.XXX

Your code takes that and:

foreach address in ...
	requests.post(..... XX.XX.XXX.17/28

[icanhazpython]

If you have the ip with mask on CIDR form, just do the following request:

/api/ipam/prefixes/?parent=10.0.0.1%2F24

In my test it returns the parent prefix of 10.0.0.0/24.

Edit: Just noticed that you said you didn't have the prefix length. But you do, if you have ARP then you have a layer 3 interface and that interface has a mask set, right?

It appears that this is incorrect.
For those looking for this feature, the query param is actually "?contains=".