IP address classes vs CIDR (was Re: Reviving ARPAnet)
cctalk at gtaylor.tnetconsulting.net
Thu Jan 18 12:35:57 CST 2018
On 01/18/2018 11:00 AM, Eric Smith wrote:
> Years ago I added a configurable "bozo-arp" feature to the Telebit
> NetBlazer router, which would respond to ARP requests for non-local
> addresses and reply with the router's MAC address (on that interface),
> specifically in order to make classful-only hosts work on a CIDR
That functionality sounds exactly like my understanding of what Proxy
ARP is supposed to do.
> Later someone paid me to write a NetBSD daemon ("anyipd") to do the same
> thing, though for an entirely different reason.
Since you stated that anyipd "…would respond to ARP requests for
non-local addresses…" I"m assuming that you are talking IP and not
another protocol. Please correct me if I'm assuming incorrectly.
> Recently I've needed that functionality on Linux, as I have multiple
> old systems that only understand classful, including the AT&T UnixPC
> (7300 or 3B1). I suppose I should rewrite and open-source it.
I'm trying to make sure that I understand what you're wanting / needing
to do and evaluate if Proxy ARP can do it or not.
I'm guessing that you have a host, AT&T Unix PC, that's at (for the sake
of discussion) 10.20.30.40/8 and you'd like to communicate with another
machine that's at 10.10.10.10/24. Obviously 10.10.10.10/24 is a subset
of 10.0.0.0/8, so the AT&T Unix PC thinks that 10.10.10.10 is local. -
Does this accurately represent your use case?
Unless you correct me, I'm going to assume that this is accurate enough
for the sake of discussion.
I /think/ (it's been too long since I've done this) that you would
configure one classless interface with 10.20.30.254/24 and another
classless interface with 10.10.10.254/24 -and- enable Proxy ARP on both
(?) interfaces. You will likely need to enter the target machine's IP
addresses in a file that the Proxy ARP sub-system references to learn
what target IPs that it needs to Proxy ARP for.
I might not have the nuances exactly correct because I've not done this
in a long time. But I have made this scenario work with the Proxy ARP
support that currently exists in the Linux kernel.
So … I wonder what additional functionality your anyipd would provide.
- I'm actually quite curious to learn.
Grant. . . .
unix || die
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