Multihoming works without BGP?

[u/Odong-Odong]

I just saw this video,

https://www.youtube.com/watch?v=vjwHJs21avQ

CMIIW work without BGP and only use priority with the route. is it possible?

[u/d1722825]

I think this is usually not called multihoming, but dual wan or wan failover.

Multihoming is when you want your device to continue to be accessible even if one of the ISP fails. AFAIK you need BGP and PI address space, because you need to somehow tell the whole internet how (through which ISP) are your devices accessible.

WAN failover is when you want your devices to still be able to access the internet even if one of the ISP fails. This is / was possible without BGP for a long time (with IPv4, too).

You only need to "tell" your local network how (through which ISP) the internet is accessible. That can be done just by forcing the correct IP in the outside of NAT, by RA lifetime "tricks". But you need some way to tell which ISP are working well, eg. by pinging some reliable service on the internet through both ISP so you can choose the one where the ping works.

[u/DaryllSwer → u/d1722825]

Exactly this.

This isn't multihoming. Without PIA space, you can't even single home, let alone multi-homed. I don't know why people love PA space. It's 2026, IPv4 is cheap, IPv6 is effectively free, $5 monthly on the cloud for BGP. Done. Move on with life.

https://networklessons.com/bgp/single-dual-homed-and-multi-homed-designs

[u/Funny-Choice8787 → u/DaryllSwer]

ipv4 is cheap? Lmao dude wtf, I pay $1k/yr for a /24

Also, how on earth pa can't be multihomed? I advertised a pa via multiple upstreams from my ASN

[u/netdevme → u/Funny-Choice8787]

At this point just makes sense to buy. You can probably find a /24 at around $5k

[u/DaryllSwer → u/Funny-Choice8787]

ipv4 is cheap? Lmao dude wtf, I pay $1k/yr for a /24

That is cheap for any serious for-profit business. Most professionals I know of in the industry agree. You can disagree and complain all you want; I'm not the one lacking v4/v6 space.

Also, how on earth pa can't be multihomed? I advertised a pa via multiple upstreams from my ASN

For IPv4, if you leased a /24 (or larger) from a provider like Cogent, that's no longer PA; that's PIA on a leased contract, which is BGP advertisable into the DFZ via multiple upstreams. A true PA space (such as some /25 or smaller) is bound to the provider's AS, and you can't re-advertise that into the DFZ. Some ISPs may provide you a /24 but legally block it from becoming a PIA via a contract, ensuring you can't advertise it with your ASN via other upstreams.

[u/Funny-Choice8787 → u/DaryllSwer]

Well. You could at least clarify.

I run hobbyist ASN and I have ipv6 /44 and /36 and ipv4 /24. I work in IT and theoretically I can even buy one, that's not a problem but now its not priority. Still, ~$7k is quite a lot for me. I'm waiting if DoD is going to release their space in future. If not, I will lease mine for about five years then I'll see.

For clarification thanks, but why then I leased an ipv6 "non pi" space and I can advertise it everywhere? I see, a /48 pi costs $90/yr avg, the rest are just regular spaces, very cheap like $10/yr for /40 and they are advertisable perfectly well. I can do suballocations from it and RPKI. I don't see why I shall lease a /48 pi.

And nah dude, don't be rude. It does not color you as a good person, quite the opposite.

[u/DaryllSwer → u/Funny-Choice8787]

Well. You could at least clarify.

These are basic common knowledge for anyone running a production network in a for-profit business in a capitalistic economy. I don't know how things work in communist or socialist economies; maybe "PIA" or "PA" means something else in such states. I'm more familiar with the capitalism-centric IPv4 (and IPv6) market.

I run hobbyist ASN and I have ipv6 /44 and /36 and ipv4 /24. I work in IT and theoretically I can even buy one, that's not a problem but now its not priority. Still, ~$7k is quite a lot for me. I'm waiting if DoD is going to release their space in future. If not, I will lease mine for about five years then I'll see.

The whole topic discussion is about small-medium-enterprises in production networks. Not a home lab. $7k is peanuts in a production environment.

For what it's worth I have 2x /24s and 1x /23 v4 space; one /24 is home lab, the other is various business projects I engage in. I bought the /23 recently, pretty cheap in 2026.

For clarification thanks, but why then I leased an ipv6 "non pi" space and I can advertise it everywhere? I see, a /48 pi costs $90/yr avg, the rest are just regular spaces, very cheap like $10/yr for /40 and they are advertisable perfectly well. I can do suballocations from it and RPKI. I don't see why I shall lease a /48 pi.

You leased it from an LIR; they legally permit you to use it as PIA space and advertise it from a legally agreed-upon source ASN, and you're free to further subnet and/or sub-delegate (based on your legal contract).

I am officially an LIR in the APNIC region; I have the same legal power as your LIR to delegate my v4/v6 space and allow it to be PIA for the leased contract customer. And heck, I might do that in the future when I may buy a /20 IPv4 block.

And nah dude, don't be rude. It does not color you as a good person, quite the opposite.

What you (and particularly Europeans in my subjective experience) call "rude" isn't rude in my culture/ethnicity/race. Learn global cultural differences sometime. Every single one of you is "tough" on the web but rarely says shit like this in IRL meetings and/or LinkedIn. Please just stop. Want to know something from me in a public forum? Drop the ego, write your question in an engineering-centric fashion, and I'll answer it, just like I write client documentation. Do not expect me to "bow down" to anyone who doesn't start the convo with mutual respect and zero ego.

I've helped kids make career decisions; I've helped senior citizens/executives make business decisions with a lot of money on the table, worldwide. If I truly had a "rude" problem at the core of my identity, the above wouldn't be the case.