# Use multicast for IPv4 local announcement
**URL:** https://forum.syncthing.net/t/use-multicast-for-ipv4-local-announcement/992
**Category:** Development
**Created:** [September 24, 2014, 11:26am UTC](https://forum.syncthing.net/t/use-multicast-for-ipv4-local-announcement/992 "2014-09-24T11:26:53Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@hobarrera](https://forum.syncthing.net/u/hobarrera)
#### Post date: [September 24, 2014, 11:26am UTC](https://forum.syncthing.net/t/use-multicast-for-ipv4-local-announcement/992/1 "2014-09-24T11:26:53Z")
Broadcast is bad. So bad it’s even been removed from IPv6.
Broadcast adds a lot of noise to the whole network - something that machines not running syncthing don’t care about. Especially in crowded/popular networks.
There’s no valid reason to use broadcast on the TCP layer any more, and multicast can perfectly cover the needs of local announcement.
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### Author:  [@jpjp](https://forum.syncthing.net/u/jpjp)
#### Post date: [September 24, 2014, 2:08pm UTC](https://forum.syncthing.net/t/use-multicast-for-ipv4-local-announcement/992/2 "2014-09-24T14:08:31Z")
Broadcast is more reliable on ipv4. Multicast is used for ipv6. See [https://github.com/syncthing/syncthing/issues/217](https://github.com/syncthing/syncthing/issues/217)
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### Author:  [@hobarrera](https://forum.syncthing.net/u/hobarrera)
#### Post date: [September 24, 2014, 2:24pm UTC](https://forum.syncthing.net/t/use-multicast-for-ipv4-local-announcement/992/3 "2014-09-24T14:24:19Z")
> [@jpjp](#):
>
> Broadcast is more reliable on ipv4. Multicast is used for ipv6. See [Local discovery is far too fragile · Issue #217 · syncthing/syncthing · GitHub](https://github.com/syncthing/syncthing/issues/217)
multicast is ridiculously standard. Even stuff like mDNS uses multicast (that’s what the _m_ is for). Do you have any citation on why it’s unreliable? I’ve used it every day during years to access hosts on my LAN (since discovery is done via mDNS).
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### Author:  [@jpjp](https://forum.syncthing.net/u/jpjp)
#### Post date: [September 24, 2014, 2:36pm UTC](https://forum.syncthing.net/t/use-multicast-for-ipv4-local-announcement/992/4 "2014-09-24T14:36:04Z")
It didn’t work well on ipv4, that’s why it was switched back. Sorry.
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### Author:  [@calmh](https://forum.syncthing.net/u/calmh)
#### Post date: [September 24, 2014, 6:35pm UTC](https://forum.syncthing.net/t/use-multicast-for-ipv4-local-announcement/992/5 "2014-09-24T18:35:11Z")
> [@hobarrera](#):
>
> Do you have any citation on why it’s unreliable?
I’ll repeat here what I just said in the ticket; search the forum. The current solution mostly just works. Using multicast didn’t. Android does weird stuff with it; firewalls handle it differently, etc.
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### Author:  [@system](https://forum.syncthing.net/u/system)
#### Post date: [May 12, 2017, 1:19pm UTC](https://forum.syncthing.net/t/use-multicast-for-ipv4-local-announcement/992/6 "2017-05-12T13:19:51Z")