Level 3 BGP Advertisements

james machado hvgeekwtrvl at gmail.com
Wed Aug 29 17:30:22 CDT 2012


On Wed, Aug 29, 2012 at 1:55 PM, STARNES, CURTIS
<Curtis.Starnes at granburyisd.org> wrote:
> Sorry for the top post...
>
> Not necessarily a Level 3 problem but;
>
> We are announcing our /19 network as one block via BGP through AT&T, not broken up into smaller announcements.
> Earlier in the year I started receiving complaints that some of our client systems were having problems connecting to different web sites.
> After much troubleshooting I noticed that in every instance the xlate in our Cisco ASA for the client's IP last octet was either a 0 or 255.
> Since I am announcing our network as a /19, the subnet mask is 255.255.224.0, that would make our network address x.x.192.0 and the broadcast x.x.223.255.
> So somewhere the /24 boundary addresses were being dropped.
>
> Just curious if anyone else has seen this before.

some OS's by M and others as well as some devices have IP stacks which
will not send or receive unicast packets ending in 0 or 255.  have had
casses where someone was doing subnets that included those in the DCHP
scopes and the computers that received these addresses were black
holes.

james



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