<p>The network magic is not supposed to be mutable. The only reason it's in the Shelley Genesis is because the Shelley Genesis simplified the Byron genesis file format significantly and allows the code to &quot;ignore&quot; the mess of the Byron genesis file as soon as it reaches the Shelley era. Newer era Genesis files are additive to the Shelley era rather than a replacement like we had from Byron to Shelley transition.</p>

CC BY-SA 4.0
2022-01-31T16:44:44.650Z
OK, I think I more or less get it, but the magic number is a random number which is unique to the testnet 'version' or something? So, when things change, this number may change, but it's not supposed to change? That makes a bit of sense.
Now, what's with the Alonzo Era which is actually the Goguen era?
Kurt Sys
CC BY-SA 4.0
2022-01-30T13:25:18.657Z
2022-01-30T13:25:18.657Z
Samuel Leathers
<p>I'm a but confused with the magic number in the testnet:</p>
<ul>
<li>when we execute a transaction with the cli <code>cardano-cli run transaction</code> , we run it in the alonzo-era. when we check for the
magic number, we have to check the networkMagic field in
<code>testnet-shelly-geneisis.json</code></li>
</ul>
<p>There doesn't seem to be a networkMagic in <code>testnet-alonzo-genesis.json</code>, although there is in both the shelly and byron config files, and it's the same networkMagic in these two configs.</p>
<p>Can someone explain how this works with the magic number and the era's?</p>
<p>(As a small side question, why is it actually called the Alonzo era, while we're in the Cardano Goguen era? For the first two, they use the same era names, for the one we're in now, it's another name. It's a bit confusing.)</p>

<plutus-pioneer-program><testnet><alonzo>
how does the magic number work for different era's?
# how does the magic number work for different era's?

(Asked by: username_0 on 2022-01-30)

I'm a but confused with the magic number in the testnet:

* when we execute a transaction with the cli `cardano-cli run transaction` , we run it in the alonzo-era. when we check for the
  magic number, we have to check the networkMagic field in
  `testnet-shelly-geneisis.json`

There doesn't seem to be a networkMagic in `testnet-alonzo-genesis.json`, although there is in both the shelly and byron config files, and it's the same networkMagic in these two configs.

Can someone explain how this works with the magic number and the era's?

(As a small side question, why is it actually called the Alonzo era, while we're in the Cardano Goguen era? For the first two, they use the same era names, for the one we're in now, it's another name. It's a bit confusing.)

**Tags:** plutus-pioneer-program, testnet, alonzo

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## 1 answers

### Answer by username_1 on 2022-01-30. Score: 2

The network magic is not supposed to be mutable. The only reason it's in the Shelley Genesis is because the Shelley Genesis simplified the Byron genesis file format significantly and allows the code to "ignore" the mess of the Byron genesis file as soon as it reaches the Shelley era. Newer era Genesis files are additive to the Shelley era rather than a replacement like we had from Byron to Shelley transition.

> **Comments:**
> **username_0**: OK, I think I more or less get it, but the magic number is a random number which is unique to the testnet 'version' or something? So, when things change, this number may change, but it's not supposed to change? That makes a bit of sense. Now, what's with the Alonzo Era which is actually the Goguen era?  

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