Static Routing 172.16.0.0/32

Ken Chase math at sizone.org
Fri Dec 8 22:44:11 CST 2017


why not use 192.0.2.0/24 addrs?

lots of other ranges you could probably use safely.

   https://en.wikipedia.org/wiki/Reserved_IP_addresses

Using .0 you're asking to exercise bugs and undefined implimentation choices
of various tcp stacks and resolvers out there on myriad devices. Clever collision
avoidance, but relies on a prayer.

(IIRC try setting an NS record to resolve to 127.0.0.255 on windows 95 - it
used to lock the OS up.... fun times. Someone had pointed some popular domain
at us by accident, and having no entry and no negative caching of the day
meant we were being hammerred on our 10mbps uplink, had to set something to
get cached, so we did... several hours later a microsoft engineer called us
and pleaded with us to use a different IP. :)

/kc


On Fri, Dec 08, 2017 at 05:25:58PM -0500, William Herrin said:
  >On Fri, Dec 8, 2017 at 4:50 PM, Ryan Hamel <Ryan.Hamel at quadranet.com> wrote:
  >>
  >> I'm not implying HTTP, I'm implying a static route at each sites private
  >layer 3 router (it'll move to BGP in the future). The repository server
  >listens on the IP as well.
  >>
  >> My original question was the fact of using 172.16.0.0/32 as a usable IP
  >address (not even caring about anycast).
  >
  >> Internal private network that is reachable by clients.
  >
  >Hi Ryan,
  >
  >Clients meaning employee computers or clients meaning other networks who
  >subscribe to your service and connect with a VPN?
  >
  >The the former, save yourself grief and use a different /32.
  >
  >For the latter, it's semi-clever. It neatly avoids the problem of customers
  >using the same RFC1918 addresses as you. Even if they're using a subnet
  >like 172.16.0.0/24, a /32 route can usually override that one address
  >without ill effect.
  >
  >It's only semi-clever because the .0 address is a corner case in the code
  >and corner cases are where bugs are most likely to happen.  And if you're
  >sending clients from that address to another host with a regular 172.16
  >address anyway...
  >
  >Regards,
  >Bill Herrin
  >
  >
  >
  >
  >>
  >>
  >> -------- Original message --------
  >> From: William Herrin <bill at herrin.us>
  >> Date: 12/8/17 1:45 PM (GMT-08:00)
  >> To: Ryan Hamel <Ryan.Hamel at quadranet.com>
  >> Cc: nanog at nanog.org
  >> Subject: Re: Static Routing 172.16.0.0/32
  >>
  >> On Fri, Dec 8, 2017 at 4:37 PM, Ryan Hamel <Ryan.Hamel at quadranet.com>
  >> wrote:
  >> > 1. A single known ip address that redirects to the closest internal repo
  >> server. 172.16.0.0/32 redirects to a usable subnet ip in 172.16.xx.xx by
  >> static route.
  >>
  >> Hi Ryan,
  >>
  >> Maybe if would help if you write the extended version because that's about
  >> as clear as mud. First you asked about routing. Now you imply HTTP.
  >>
  >> Regards,
  >> Bill Herrin
  >>
  >>
  >> --
  >> William Herrin ................ herrin at dirtside.com  bill at herrin.us
  >> Dirtside Systems ......... Web: <http://www.dirtside.com/>
  >>
  >
  >
  >
  >-- 
  >William Herrin ................ herrin at dirtside.com  bill at herrin.us
  >Dirtside Systems ......... Web: <http://www.dirtside.com/>

-- 
Ken Chase - math at sizone.org Guelph Canada


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