We use BGP quite heavily at work, and even though I'm not interacting with that directly, it feels like it's something very useful to learn at least on some basic level. The most effective and fun way of learning technology is finding some practical application, so I decided to see if it could help to improve networking management for my Virtual Machines.
My setup is fairly simple: I have a host that runs bhyve VMs and I have a desktop system from where I ssh to VMs, both hosts run FreeBSD. All VMs are connected to each other through a bridge and have a common network 10.0.1/24. The point of this exercise is to be able to ssh to these VMs from desktop without adding static routes and without adding vmhost's external interfaces to the VMs bridge.
I've installed openbgpd on both hosts and configured it like this:
vmhost: /usr/local/etc/bgpd.conf
AS 65002
router-id 192.168.87.48
fib-update no
network 10.0.1.1/24
neighbor 192.168.87.41 {
descr "desktop"
remote-as 65001
}
Here, router-id is set vmhost's IP address in my home network (192.168.87/24), fib-update no is set to forbid routing table update, which I initially set for testing, but keeping it as vmhost is not supposed to learn new routes from desktop anyway. network announces my VMs network and neighbor describes my desktop box.
Now the desktop box:
desktop: /usr/local/etc/bgpd.conf
AS 65001
router-id 192.168.87.41
fib-update yes
neighbor 192.168.87.48 {
descr "vmhost"
remote-as 65002
}
It's pretty similar to vmhost's bgpd.conf, but no networks are announced here, and fib-update is set to yes because the whole point is to get VM routes added.
Both hosts have to have the openbgpd service enabled:
/etc/rc.conf.local
openbgpd_enable="YES"
Now start the service (or wait until next reboot) using service openbgpd start and check if neighbors are there:
vmhost: bgpctl show summary
$ bgpctl show summary
Neighbor AS MsgRcvd MsgSent OutQ Up/Down State/PrfRcvd
desktop 65001 1089 1090 0 09:03:17 0
$
desktop: bgpctl show summary
$ bgpctl show summary
Neighbor AS MsgRcvd MsgSent OutQ Up/Down State/PrfRcvd
vmhost 65002 1507 1502 0 09:04:58 1
$
Get some detailed information about the neighbor:
desktop: bgpctl sh nei vmhost
$ bgpctl sh nei vmhost
BGP neighbor is 192.168.87.48, remote AS 65002
Description: vmhost
BGP version 4, remote router-id 192.168.87.48
BGP state = Established, up for 09:06:25
Last read 00:00:21, holdtime 90s, keepalive interval 30s
Neighbor capabilities:
Multiprotocol extensions: IPv4 unicast
Route Refresh
Graceful Restart: Timeout: 90, restarted, IPv4 unicast
4-byte AS numbers
Message statistics:
Sent Received
Opens 3 3
Notifications 0 2
Updates 3 6
Keepalives 1499 1499
Route Refresh 0 0
Total 1505 1510
Update statistics:
Sent Received
Updates 0 1
Withdraws 0 0
End-of-Rib 1 1
Local host: 192.168.87.41, Local port: 179
Remote host: 192.168.87.48, Remote port: 13528
$
By the way, as you can see, bgpctl supports shortened commands, e.g. sh nei instead of show neighbor.
Now look for that VMs route:
desktop: bgpctl show rib
$ sudo bgpctl show rib
flags: * = Valid, > = Selected, I = via IBGP, A = Announced, S = Stale
origin: i = IGP, e = EGP, ? = Incomplete
flags destination gateway lpref med aspath origin
*> 10.0.1.0/24 192.168.87.48 100 0 65002 i
$
So that VMs network, 10.0.1/24, it's there! Now check if the system routing table was updated and has this route:
desktop
$ route -n get 10.0.1.45
route to: 10.0.1.45
destination: 10.0.1.0
mask: 255.255.255.0
gateway: 192.168.87.48
fib: 0
interface: re0
flags:
recvpipe sendpipe ssthresh rtt,msec mtu weight expire
0 0 0 0 1500 1 0
$ ping -c 1 10.0.1.45
PING 10.0.1.45 (10.0.1.45): 56 data bytes
64 bytes from 10.0.1.45: icmp_seq=0 ttl=63 time=0.192 ms
--- 10.0.1.45 ping statistics ---
1 packets transmitted, 1 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.192/0.192/0.192/0.000 ms
$
Whoa, things work as expected!
Conclusion
As mentioned already, similar result could be achieved without using BGP by using either static routes or bridging interfaces differently, but the purpose of this exercise is to get some basic hands-on experience with BGP. Right now I'm looking into extending my setup in order to try more complex BGP schema. I'm thinking about adding some software switches in front of my VMs or maybe adding a second VM host (if budget allows). You're welcome to comment if you have some ideas how to extend this setup for educational purposes in the context of BGP and networking.
As a side note, I really like openbgpd so far. Its configuration file format is clean and simple, documentation is good, error and information messages are clear, and CLI has intuitive syntax.
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