Lab 09-01 · E-mail from the router¶

Your phone tells you when a parcel is out for delivery. Your bank sends you an e-mail when someone uses your card. Machines that work alone, day and night, need a way to tell a human that something happened.

A router is one of those machines. It sits in a cupboard, nobody looks at it, and one day the configuration you spent a whole afternoon on is gone. Wouldn't it be nice if the router had mailed you a copy of its configuration every night? In this lab you teach r1 to send e-mails, and then to send its own configuration as an attachment.

How e-mail travels: the post office¶

An SMTP server (Simple Mail Transfer Protocol) is the computer that accepts e-mails from senders and delivers them towards the recipient's mailbox.

The analogy for this whole lab: e-mail is the post office. The router writes a letter (the e-mail), but it cannot walk to your house. It drops the letter at the post office (the SMTP server), and the post office puts it in your mailbox (the inbox you read).

flowchart LR
    R1["<b>r1</b><br>writes the letter<br>/tool e-mail send"]
    SMTP["<b>SMTP server</b><br>the post office<br>mailpit · port 1025"]
    BOX["<b>Inbox</b><br>your mailbox<br>web on port 8025"]
    YOU["<b>You</b><br>read it"]
    R1 -->|"SMTP"| SMTP
    SMTP -->|"stores"| BOX
    BOX -->|"web / API"| YOU

So the router needs to know three things, exactly what you write on the envelope at a post office counter:

The scenario¶

flowchart LR
    INET["<b>internet</b><br>198.51.100.10"]
    CAP["<b>class-ap</b><br>10.0.0.1 · 198.51.100.1"]
    subgraph R1["r1 · your router"]
        WAN["ether2 (WAN)<br>10.0.0.x by DHCP"]
        BR["<b>bridge1</b><br>192.168.88.1/24"]
    end
    PC1["<b>pc1</b><br>your laptop<br>DHCP 192.168.88.x"]
    MAIL["<b>mailpit</b><br>the post office<br>192.168.88.25"]
    INET ---|"198.51.100.0/24"| CAP
    CAP ---|"10.0.0.0/24"| WAN
    WAN --- BR
    BR ---|"ether3"| PC1
    BR ---|"ether4"| MAIL

Start the lab¶

Download the lab files and unzip them: 09-01-email.zip. Open a terminal inside the 09-01-email folder.

sudo containerlab deploy -t topology.clab.yml

Give RouterOS about two minutes to boot. Then open two terminals:

ssh admin@clab-mtcna-09-01-r1                 # password: admin
docker exec -it clab-mtcna-09-01-pc1 bash

At any moment, CLAB_EXEC="docker exec" ./check.sh tells you what is already solved.

Step 1 · Look inside the empty mailbox¶

Before sending anything, check that the post office is open and the mailbox is empty. Mailpit has an API (a web address that answers with data instead of a pretty page), so you can read the inbox with curl.

On pc1:

curl -s http://192.168.88.25:8025/api/v1/messages

Expected: {"total":0,"unread":0,...,"messages":[]}. Zero messages.

On r1, check that the router can reach the mail server at all:

/ping 192.168.88.25 count=3

Done when the inbox is empty and r1 pings 192.168.88.25.

Step 2 · Tell the router where the post office is¶

WinBox: Tools → Email. Server 192.168.88.25, Port 1025, TLS no, From r1@mtcna.lab. Apply.

/tool e-mail set server=192.168.88.25 port=1025 from="r1@mtcna.lab" tls=no
/tool e-mail print

Expected output (part):

    server: 192.168.88.25
      port: 1025
       tls: no
      from: r1@mtcna.lab

Done when /tool e-mail print shows the server and port above.

Step 3 · Send a test e-mail¶

Always test the simplest thing first: a short e-mail with no attachment.

/tool e-mail send to="you@mtcna.lab" subject="Hello from r1" body="My first e-mail sent by a router."
/log print where topics~"e-mail"

Expected in the log: e-mail,info sent <Hello from r1> to: you@mtcna.lab.

Now the important part: check the mailbox, not only the log. On pc1:

curl -s http://192.168.88.25:8025/api/v1/messages | python3 -m json.tool | grep -E '"Subject"|"Address"'

You should see the subject Hello from r1, from r1@mtcna.lab to you@mtcna.lab.

Done when the test e-mail is in mailpit's inbox.

Step 4 · Export the configuration and mail it¶

An export is the configuration written as RouterOS commands in a text file (.rsc). If the router dies, you paste that file into a new one and it is back. That is exactly what you want to keep somewhere safe.

WinBox: New Terminal, or Files to see the result.

/export file=export
/file print where name~"export"

Expected: a file export.rsc of about 1 KiB. Now send it as an attachment, with the slides' subject and body:

/tool e-mail send to="you@mtcna.lab" subject="$[/system identity get name] export" body="$[/system clock get date] configuration file" file=export.rsc

The $[ ... ] parts are small commands that RouterOS runs before sending: $[/system identity get name] becomes r1, and $[/system clock get date] becomes today's date. So the subject arrives as r1 export.

Done when mailpit shows an e-mail r1 export with the attachment export.rsc.

Step 5 · Make it one command: a script¶

Typing two long commands every night is not going to happen. A script is a saved list of commands with a name. Run the name, and the router does all the steps.

WinBox: System → Scripts → +. Name email-export, paste the source below into Source. OK.

/system script add name=email-export comment="export the config and e-mail it" source={/export file=export; :delay 2s; /tool e-mail send to="you@mtcna.lab" subject="$[/system identity get name] export" body="$[/system clock get date] configuration file" file=export.rsc; :log info "email-export: sent"}
/system script run email-export
/log print where message~"email-export"

• The { ... } braces keep the source as text: the $[ ... ] parts are evaluated each time the script runs, not when you create it.
• :delay 2s gives the export time to finish writing the file before it is attached.
• :log info leaves a trace in the log, so you can see that the script ran.

Done when /system script run email-export makes a new r1 export e-mail appear in mailpit. Run CLAB_EXEC="docker exec" ./check.sh: it must end with RESULT: lab solved.

If something goes wrong¶

Clean up¶

sudo containerlab destroy -t topology.clab.yml --cleanup

Key takeaways¶

• A router sends e-mail through an SMTP server, the post office: you configure server, port and from in Tools → Email.
• /tool e-mail send can attach a file, for example the export of the configuration.
• $[ ... ] inserts the result of a command (identity, date) into the text when it runs.
• A script turns several commands into one; the scheduler can run it every night.
• The log line sent means the server accepted the e-mail; only the inbox proves it arrived.

Quick check¶

Next: instead of you asking the router, the router watches other machines and reacts by itself: Netwatch.