[PATCH] Preserve MED from eBGP peers

[Ondrej Zajicek]

On Tue, Dec 08, 2020 at 09:02:15AM -0800, Trisha Biswas wrote:
> Hi all,
> 
> The attached patch helps preserve MED values to/from eBGP peers. When
> propagating a route from a true eBGP peer to an internal peer, this avoids
> resetting the MED attribute to allow propagation of MED to/from external
> peers. This is enabled via a configuration line: "preserve med", which goes
> under BGP configs. Without the configuration line this would be a no-op.

Hi

I am bit hesitant with this patch. Seems to me that it is something that
could be easily done with 'bgp_med = bgp_med;' export filter, but that
may be tricky for users that are not thoroughly familiar with bgp_med
behavior.

Also, your description seems confusing. When a route is propagated from
EBGP to an internal peer, then MED is preserved regardless of this.
It is just propagation to EBGP peer when original MED is stripped.

What is a use case for this option? Does other BGP implementations
(Juniper, Cisco) have some similar option?

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."