ES site-local addressing scheme

ldenitto · October 2, 2019, 4:33pm

I'm fairly new to ES and looking forward to implementing it in my environment. When going through the config documentation, I came across this:

https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-network.html#network-interface-values and have a question regarding the site parameters. It mentions "Any site-local addresses on the system, for example 192.168.0.1."

Where/how are these site local address subnets determined/assigned? Where/how are they sourced?

Apologies if this question is a bit unclear and I can clarify further if needed. Any help is appreciated.

DavidTurner · October 2, 2019, 4:49pm

It means any of your machine's local addresses that match this check:

github.com

openjdk/jdk/blob/9d764ee48ee7c2e7be7a25aee2ed7bed2fcd2000/src/java.base/share/classes/java/net/Inet4Address.java#L210-L221


public boolean isSiteLocalAddress() {
    // refer to RFC 1918
    // 10/8 prefix
    // 172.16/12 prefix
    // 192.168/16 prefix
    int address = holder().getAddress();
    return (((address >>> 24) & 0xFF) == 10)
        || ((((address >>> 24) & 0xFF) == 172)
            && (((address >>> 16) & 0xF0) == 16))
        || ((((address >>> 24) & 0xFF) == 192)
            && (((address >>> 16) & 0xFF) == 168));
}

So that's the subnets 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.

system · October 30, 2019, 4:49pm

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