[c-nsp] eBGP via loopback

[Steve Bertrand]

Aaron wrote:
> Did you setup ebgp multihop since you are doing peering to the loopbacks?

Yes.

> Curious on why you would want to use the loopback instead of the 
> interface for ebgp. Definitely not the recommended way unless you are 
> trying to load balance on multiple links.

Here is my (slightly edited) response to someone else who emailed me 
off-list:

To be honest, the loopback over eBGP was not an intended design goal. It 
just so happened that I had this particular router in an iBGP mesh (lab 
environment), and realized I wanted to push the router to a remote 
location and gain practical experience on how to conceptually implement 
a no-export community for a private ASN.

I overlooked the loopback addresses when I put the router in its own AS, 
due to the fact the PtP addresses did not need to change. I just threw 
in the ebgp-multihop blindingly instead of renumbering the neighbors and 
the update-source.

Most likely, I would not have even payed any attention to the 
configuration until later review if I hadn't have had the packet loss 
problem.

---

For the sake of completeness, the router that was swallowing the packets 
  is running Quagga on FreeBSD. I had forgotten to set the ip.forwarding 
sysctl variable to true.

Steve