nanog mailing list archives
Re: Anycast but for egress
From: Bill Woodcock <woody () pch net>
Date: Wed, 28 Jul 2021 07:49:28 -0700
On Jul 27, 2021, at 6:15 PM, Vimal <j.vimal () gmail com> wrote: AWS Global Accelerator gives anycast IPs that's good for ingress, but my original question was about having predictable egress IPs. It looks like having a few EIPs/a contiguous network block is the way to go.
Yes. Predictable and unchanging (but each unique per location) static IP addresses is what you’re looking for. It would be a huge convenience to others if you could specify a single contiguous CIDR block for others to “permit” in their access control lists, but alas that would be very difficult as well… Since BGP announcements generally need to be aggregated up to at least a /24 or a /48 (though people are less strict on the v6 side), each group of hosts numbered from the same block of that size would need to have internally contiguous convex routing, meaning that it would have to be interconnected by its own network (albeit that could be tunnels) and accept inbound traffic at any point on the surface of that network, backhauling it to the appropriate location. So if you wanted to be able to identify a single CIDR block with eight locations in it, you’d either need to specify a /24 that was 97% wasted, and was fully internally interconnected (i.e. no efficiencies in localizing traffic), or you’d need to advertise eight /24s, which would aggregate up to a single /21, which was 99.6% wasted. So, you can see why the combination of scarce IPv4 addresses, scarce BGP routing slots, and content routing tricks often don’t play well together. -Bill
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Current thread:
- Re: Anycast but for egress, (continued)
- Re: Anycast but for egress Owen DeLong via NANOG (Jul 27)
- Re: Anycast but for egress Daniel Corbe (Jul 27)
- Re: Anycast but for egress Bill Woodcock (Jul 27)
- Re: Anycast but for egress Mark Tinka (Jul 27)
- Re: Anycast but for egress Matt Harris (Jul 27)
- Re: Anycast but for egress Adam Thompson (Jul 27)
- Re: Anycast but for egress Vimal (Jul 28)
- Re: Anycast but for egress Daniel Corbe (Jul 27)
- Re: Anycast but for egress Andras Toth (Jul 27)
- Re: Anycast but for egress Vimal (Jul 28)
- Re: Anycast but for egress Bill Woodcock (Jul 28)
- Re: Anycast but for egress Vimal (Jul 28)
- Re: Anycast but for egress Baldur Norddahl (Jul 28)
- Re: Anycast but for egress Baldur Norddahl (Jul 28)
- Re: Anycast but for egress Mark Tinka (Jul 28)
- Re: Anycast but for egress Randy Bush (Jul 28)
- Re: Anycast but for egress Bill Woodcock (Jul 28)
- Re: Anycast but for egress Mark Tinka (Jul 28)
- Re: Anycast but for egress Vimal (Jul 28)
- Re: Anycast but for egress William Herrin (Jul 28)
- Re: Anycast but for egress Glenn McGurrin via NANOG (Jul 28)
- Re: Anycast but for egress Vimal (Jul 29)