Replace 1.1 with 127.1

This avoids pinging an external machine

slides/k8s/kubectlrun.md

@@ -20,10 +20,9 @@
 
 .exercise[
 
-- Let's ping `1.1.1.1`, Cloudflare's 
-  [public DNS resolver](https://blog.cloudflare.com/announcing-1111/):
+- Let's ping the address of `localhost`, the loopback interface:
   ```bash
-  kubectl run pingpong --image alpine ping 1.1.1.1
+  kubectl run pingpong --image alpine ping 127.0.0.1
   ```
 
 <!-- ```hide kubectl wait deploy/pingpong --for condition=available``` -->
@@ -367,12 +366,12 @@ Let's leave `kubectl logs` running while we keep exploring.
 
 ## Various ways of creating resources
 
-- `kubectl run` 
+- `kubectl run`
 
   - easy way to get started
   - versatile
 
-- `kubectl create <resource>` 
+- `kubectl create <resource>`
 
   - explicit, but lacks some features
   - can't create a CronJob before Kubernetes 1.14
@@ -516,15 +515,36 @@ class: extra-details
 
 ---
 
-## Aren't we flooding 1.1.1.1?
+class: extra-details
 
-- If you're wondering this, good question!
+## Party tricks involving IP addresses
 
-- Don't worry, though:
+- It is possible to specify an IP address with less than 4 bytes
 
-  *APNIC's research group held the IP addresses 1.1.1.1 and 1.0.0.1. While the addresses were valid, so many people had entered them into various random systems that they were continuously overwhelmed by a flood of garbage traffic. APNIC wanted to study this garbage traffic but any time they'd tried to announce the IPs, the flood would overwhelm any conventional network.*
+  (example: `127.1`)
 
-  (Source: https://blog.cloudflare.com/announcing-1111/)
+- Zeroes are then inserted in the middle
 
-- It's very unlikely that our concerted pings manage to produce
-  even a modest blip at Cloudflare's NOC!
+- As a result, `127.1` expands to `127.0.0.1`
+
+- So we can `ping 127.1` to ping `localhost`!
+
+(See [this blog post](https://ma.ttias.be/theres-more-than-one-way-to-write-an-ip-address/
+) for more details.)
+
+---
+
+class: extra-details
+
+## More party tricks with IP addresses
+
+- We can also ping `1.1`
+
+- `1.1` will expand to `1.0.0.1`
+
+- This is one of the addresses of Cloudflare's
+  [public DNS resolver](https://blog.cloudflare.com/announcing-1111/)
+
+- This is a quick way to check connectivity
+
+  (if we can reach 1.1, we probably have internet access)