DNS seeds aren't necessarily "seednodes" as they don't necessarily have have Bitcoin running as well. Instead these hosts have standard DNS servers with A records that new Bitcoin nodes use for bootstrapping to learn of peers.
Currently, Bitcoin master shows these four:
- bitseed.xf2.org
- dnsseed.bluematt.me
- seed.bitcoin.sipa.be
- dnsseed.bitcoin.dashjr.org
Source code:
https://github.com/bitcoin/bitcoin/blob/master/src/net.cpp#L1170
// DNS seeds
// Each pair gives a source name and a seed name.
// The first name is used as information source for addrman.
// The second name should resolve to a list of seed addresses.
static const char *strDNSSeed[][2] = {
{"xf2.org", "bitseed.xf2.org"},
{"bluematt.me", "dnsseed.bluematt.me"},
{"bitcoin.sipa.be", "seed.bitcoin.sipa.be"},
{"dashjr.org", "dnsseed.bitcoin.dashjr.org"},
};
// DNS seeds
// Each pair gives a source name and a seed name.
// The first name is used as information source for addrman.
// The second name should resolve to a list of seed addresses.
static const char *strMainNetDNSSeed[][2] = {
{"bitcoin.sipa.be", "seed.bitcoin.sipa.be"},
{"bluematt.me", "dnsseed.bluematt.me"},
{"dashjr.org", "dnsseed.bitcoin.dashjr.org"},
{"xf2.org", "bitseed.xf2.org"},
{NULL, NULL}
};
