Re: Source IPv4 address selection vs BGP IX connection

mike tancsa <[email protected]>
Newsgroups gmane.os.freebsd.devel.net
Message-ID <[email protected]>
On 4/23/2024 10:12 PM, Gregory Shapiro wrote:
> Short version:
>
> Using FreeBSD as a BGP router has network issues caused by suboptimal
> default IPv4 source address selection when connected to Internet
> Exchanges (which are required to use IPs that aren't routable on the
> Internet).  I was hoping to find more elegant workarounds or encourage
> FreeBSD to add source IPv4 selection akin to the existing IPv6 source
> address selection (no_prefer_iface and prefer_source).
>
> I assume that there is a group of BGP enthusiasts using FreeBSD lurking
> on freebsd-net.  What have you done to solve this problem?
>
For DNS in such situations I start unbound locally and bind it to an 
internal interface or an IP on lo0 and then tell unbound to just use 
that IP only  (outgoing-interface IIRC) that is advertised out as a work 
around.  Its not a proper solution, but will get your resolver working 
at least. I run into this problem in layered networks where the next hop 
is often RFC 1918 addrs. I bind applications to internal NICs that have 
addresses that have routing to/from.

     ---Mike
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