Bridge Interfaces and ARPs

[Hooman Fazaeli]

On 12/3/2015 5:24 PM, Jason Van Patten wrote:
> Hey gang -
>
> I posted this to the FreeBSD user forums but figured I'd send a message off to the list to see if anyone has any input, guidance, or ideas. Emailing diagrams around isn't good form (IMHO) but having 
> a diagram handy will help with the discussion.  So please glance at:
>
> http://pics.lateapex.net/vz.png
>
> Background: I have a business class Verizon FIOS connection for Internet at home.  Along with that connection, I have 13 (not 14!) static IPs from VZ.  They almost fall within a proper CIDR block, 
> but not quite: 1.2.3.210 - 1.2.3.222.  I don't own .209, so I can't claim 1.2.3.208/28 as my IP block (dammit!)  The subnet for the static IPs is a /24, and the default route is *Verizon's* router: 
> 1.2.3.1.
>
> There are a number of different choices for this network layout: DMZ, bridging, or binat.  I chose bridging so that I don't have the complexity of binatting, and yet have some protection for the 
> servers via my router.  So, per the drawing, the FreeBSD router's em0 is connected to the Verizon equipment, while re0 and re1 are both connected to a managed Cisco switch, on different VLANs.
>
> VLAN 10 for re0: Public IPs (public services, etc)
> VLAN 20 for re1: Private IPs (NAS, wireless AP, etc)
>
> Via the router, VLAN 10 and Verizon's network are bridged together.  The bridge interface on the router has IP: 1.2.3.222/24 with a default route set to 1.2.3.1.  All servers on VLAN 10 have IPs 
> within the allocated range (.210 - .220) and the same default route.
>
> Now: the problem.  I used the LAGG'd server as an example in the diagram, but the same thing is happening with other servers: the router is learning ARP entries for the IPs I own *from* Verizon's 
> router.  As soon as the router caches that bad entry, it no longer routes traffic to those public IPs *from* VLAN 20 (private side). So, in other words, a laptop on the wireless network won't be 
> able to get to 1.2.3.215.
>
> My work-around for now has been a series of static ARP entries on the router for each of my public servers.  That seems to work fine, but I wonder if there's something I might be doing wrong?
>
> If I didn't include enough info, fire away.  Thanks!
>
Can you post the output of the following commands (on freebsd router):

# ifconfig
# ifconfig bridgeX addr
# arp -na
# netstat -nr -f inet
# sysctl net.inet.ip

-- 
Best regards
Hooman Fazaeli