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basically every device when it joins a network: (feddit.uk)
submitted 1 week ago by to c/lemmyshitpost@lemmy.world
19 comments fedilink hide all child comments
 

(have mercy on me networking nerds, I'm still learning)

(picture of SpongeBob Squarepants standing on a bench screaming) DHCPDISCOVER 255.255.255.255:67

all 19 comments

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[–] 31 points 1 week ago (4 children)

See also: WHO HAS 192.168.3.1 TELL 192.168.3.100

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    • [–] 15 points 1 week ago (4 children)

    No place like 127.0.0.1

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    • [–] 9 points 1 week ago (1 child)

    flashbacks to when I had to figure out PXE boot

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    • [–] 8 points 1 week ago (1 child)

    67

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    • [–] 6 points 1 week ago

    Fun fact, ipv6 was designed to fix this. Everything is multicast and, in theory, a switch could snoop MLD and create a nice map so that "where is the router?" Would send only to routers, and "whose got this up address?" Would send to a small group, usually with only the correct target in it.

    However, it's almost always just blasted out to everyone, and every network I've seen that has the mld snooping actually trying to do something just breaks ipv6 in various ways.

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    [–] 6 points 1 week ago

    neigh? ra!

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    [–] 2 points 1 week ago (1 child)

    Eli5?

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  • [–] 5 points 1 week ago

    When your computer connects to the network, it asks for it's address on the network. As it does not know where to ask, it sends a broadcast message to all computers on the same network (address 255.255.255.255). The service it wants to read is the DHCP service located on the servers' port 67, therefore the :67 after the address.

    The address it gets in return is always only temporary. The server admin can define how long such lease lasts, and when a computer calls the DHCP again later (before the lease runs out) it gets the same address, and the lease timer starts again.

    Some networks with high turnover (guest networks in a cafe, or similar) have rather fast lease expiries, therefor leading to regular requests.

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    • [–] 2 points 1 week ago* (last edited 1 week ago)

    All the cool kids are doing ICMPv6 router solicitation, DHCP discover is so last decade.

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