How to compare your route table isn’t missing any routes from your ansible config

REDHAT/CENTOS

Okay so those of you who use ansible like me and deal with complicated networks where they have a route list that’s a mile long on servers that you might need to migrate or copy to ansible and you want to save yourself some time and be accurate by ensuring the routes are correct and the file isn’t missing any routes as missing routes can be problematic and time consuming to troubleshoot after the fact.

Here is something cool you can do.

On your server you can

  1.  On the client server
  • You can use “ip” command with a flag r for routes

Example:

It will look look something like this.

[root@ansibleserver]# ip r
default via 192.168.1.1 dev enp0s8
default via 10.0.2.2 dev enp0s3 proto dhcp metric 100
default via 192.168.1.1 dev enp0s8 proto dhcp metric 101
10.0.2.0/24 dev enp0s3 proto kernel scope link src 10.0.2.15 metric 100
192.168.1.0/24 dev enp0s8 proto kernel scope link src 192.168.1.12 metric 101
10.132.100.0/24 dev mgt proto kernel scope link src 10.16.110.1 metric 1011
10.132.10.0/24  dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.136.100.0/24 dev mgt proto kernel scope link src 10.16.110.1 metric 1011
10.136.10.0/24  dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.134.100.0/24 dev mgt proto kernel scope link src 10.16.110.1 metric 1011
10.133.10.0/24  dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.127.10.0/24  dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.122.100.0/24 dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.134.100.0/24 dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.181.100.0/24 dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.181.100.0/24dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.247.200.0/24dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.172.300.0/24dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.162.100.0/24dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.161.111.0/24 dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.161.0.0/16   dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.233.130.0/24 dev mgt proto kernel scope link src 10.16.110.1 metric 101
10.60.140.0/24   dev mgt proto kernel scope link src 10.16.110.1 metric 101

Now what you want to do is take the all the ips that show up on “mgt” interface and put them in a text file

  • vi ips1 
  • save the file 

copy on the section of one after the other in a column and save the file.

10.132.100.0/24
10.132.10.0/24

10.136.100.0/24
10.136.10.0/24
10.134.100.0/24
10.133.10.0/24
10.127.10.0/24
10.122.100.0/24

  1. Now your ansible route section will probably look something like this…
Example of ansible yaml file “ansblefile”
routes:
    - device: mgt
      gw: 10.16.110.1
      route:
        - 10.132.100.0/24
        - 10.132.10.0/24
        - 10.136.100.0/24
        - 10.136.10.0/24
        - 10.134.100.0/24
        - 10.133.10.0/24
        - 10.127.10.0/24
        - 10.122.100.0/24
        - 10.134.100.0/24
        - 10.181.100.0/24
        - 10.181.100.0/24
        - 10.247.200.0/24
        - 10.172.300.0/24
        - 10.162.100.0/24
        - 10.161.111.0/24
        - 10.161.0.0/16
        - 10.233.130.0/24
  1. So you what you want to do now is copy and paste the routes from the file so they line up perfectly with the correct spacing in your yaml file.Note:
    If they aren’t lined up correctly your playbook will fail.
  2. So you can either copy them into a text editor like textpad or notepad++ and just use the replace function to add the “- “ (8 spaces before the – and 1 space before the – and ip) or  you can you perl or sed  script to do it right from the command line.
# If you want to edit the file in-place
sed -i -e 's/^/prefix/' file

Example:

sed -e 's/^/ - /' ips1 > ips2
  1. Okay now you should have a new file called ips2 that looks like below with 8 space from the left margin.
– 10.136.100.0/24
–  10.136.10.0/24
– 10.134.100.0/24
– 10.133.10.0/24
– 10.127.10.0/24
– 10.122.100.0/24
  1. Now you if you cat that ips2
  • cat ips2
  • Then highlight everything inside the file
[highlighted]
- 10.136.100.0/24
- 10.136.10.0/24
- 10.134.100.0/24
- 10.133.10.0/24
- 10.127.10.0/24
- 10.122.100.0/24
[highlighted]

7. Open your ansible yaml that contains the route section and just below “route:” right against the margin paste what you highlighted. Everything should line up perfectly and save the ansible file.

routes:
– device: mgt
gw: 10.16.110.1
route:
[paste highlight]
- 10.132.100.0/24
- 10.132.10.0/24
- 10.136.100.0/24
- 10.136.10.0/24
- 10.134.100.0/24
- 10.133.10.0/24

[paste highlight]

Okay no we need to check to ensure that you didn’t accidently miss any routes between the route table and inside your ansible yaml.

  1. Now with the original ips1 file with just the routes table without the –
    • Make sure the ansible yaml file and the ips1 file are inside the same directory to make life easier.
  • We can run a little compare script like so
    while read a b c d e; do if [[ $(grep -w $a ansiblefile) ]]; then :; else echo $a $b $c $d $e; fi  ; done < <(cat ips1)

Note:
If there are any routes missing from the ansible file it will spit them out. You can keep running this until the list shows no results, minus any gateway ips of course.

Example:

[root@ansibleserver]# while read a b c d e; do if [[ $(grep -w $a  ansiblefile) ]]; then else echo $a $b $c $d $e; fi  ; done < <(cat ips1)
10.168.142.0/24
10.222.100.0/24
10.222.110.0/24

By Nick Tailor

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