Configurer et debuger le BGP sur un Fortinet

Everyone today speaks BGP: Cisco routers, Juniper routers and ScreenOS firewalls, Fortigate does it,even SonicWall have it as planned feature So question is not whether but how. The opportunity to see how it works on Fortigate recently presented itself and here is the sum up of how I configured and debugged Fortigate BGP set up.

Task at hand: configure BGP peering with Bogon Route project by Team Cymru www.team-cymru.org/Services/Bogons/routeserver.html . More information about the Bogon Routes can be found at the source – www.team-cymru.org/Services/Bogons . But in few words they advertise to you routes that are never to be seen in your network for legitimate reasons. Those are networks not only from RFC 1918 but those reserved by RIPE for special purposes, and those unallocated to anyone as of now.
What we need to know for this set up is this:

  • They advertise all the networks with no-export community
  • also they attach 65333:888 community (as per their site)
  • they use md5 password authentication
  • they don’t expect you to advertise to them anything
  • in advertised networks next hop is their advertising router
  • their AS number is 65333

Based on all the above my Fortigate BGP peer had to :

  • enable multihop peering
  • use MD5 password authentication
  • have route-map to attach no-export community so that we don’t inadvertently advertise learned routes to other peers ( just safety net , in case BGP peer stops attaching no-export community to their routes)
  • set next hop for the learned routes to Null 0 interface.

Let’s start configuring something. Important surprise here – in Fortigate GUI you can only set 3 parameters:
As number , Peer Ip and networks to be advertised, the rest is to be done on the command line . So here it goes
1) Configuring route-map to set no-export community on learned networks and force next hop to be some reserved Ip (192.0.2.1 ) that in turn is statically routed to Null interface ,

config router route-map
edit “NO-EXPORT”
config rule
edit 3
set set-community “no-advertise”
set set-ip-nexthop 192.0.2.1
next
end
next
End

2) Configure BGP peer

(root) # show router bgp
config router bgp
set as 65002
config neighbor
edit 84.22.96.5
set ebgp-enforce-multihop enable
set remote-as 65333
set route-map-in “NO-EXPORT”
set password “yuiyui”
next
end
config redistribute “connected”
set status enable
end

3) Configure static blackhole route for the reserved IP used as the next hop for this.

(root) # sh router static
config router static
edit 3
set blackhole enable
set dst 192.0.2.1 255.255.255.255
next
End

Validation phase.
All configs are as good as the prove that it works.

List shortly all the peers

(root) # get router info bgp summary
BGP router identifier 10.250.250.2, local AS number 65002
BGP table version is 159
2 BGP AS-PATH entries
0 BGP community entries

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
84.22.96.5   4  65333       4       6      159    0    0 00:00:48        0

Total number of neighbors 1

List all BGP neighbors and their peering state

My-FG (root) # get router info bgp neighbors
BGP neighbor is 84.22.96.5, remote AS 65333, local AS 65002, external link
  BGP version 4, remote router ID 84.22.96.5
  BGP state = Established, up for 00:00:58
  Last read 00:00:58, hold time is 180, keepalive interval is 60 seconds
  Configured hold time is 180, keepalive interval is 60 seconds
  Neighbor capabilities:
    Route refresh: advertised and received (old and new)
    Address family IPv4 Unicast: advertised and received
  Received 4 messages, 0 notifications, 0 in queue
  Sent 6 messages, 0 notifications, 0 in queue
  Route refresh request: received 0, sent 0
  Minimum time between advertisement runs is 30 seconds

 For address family: IPv4 Unicast
  BGP table version 160, neighbor version 159
  Index 3, Offset 0, Mask 0x8
  Community attribute sent to this neighbor (both)
  Inbound path policy configured
  Route map for incoming advertisements is *NO-EXPORT
  0 accepted prefixes
  19 announced prefixes
  Connections established 1; dropped 0
  External BGP neighbor may be up to 255 hops away.
Local host: 10.250.250.2, Local port: 9188
Foreign host: 84.22.96.5, Foreign port: 179
Nexthop: 10.250.250.1

See the routes learned through the BGP protocol

(root) # get router info bgp network
BGP table version is 161, local router ID is 10.250.250.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 5.0.0.0          192.0.2.1                0             0 65333 65333 i
*> 14.0.0.0         192.0.2.1                0             0 65333 65333 i
*> 23.0.0.0         192.0.2.1                0             0 65333 65333 i
*> 31.0.0.0         192.0.2.1                0             0 65333 65333 i
*> 36.0.0.0         192.0.2.1                0             0 65333 65333 i
*> 37.0.0.0         192.0.2.1                0             0 65333 65333 i
*> 39.0.0.0         192.0.2.1                0             0 65333 65333 i
*> 42.0.0.0         192.0.2.1                0             0 65333 65333 i
*> 49.0.0.0         192.0.2.1                0             0 65333 65333 i
*> 100.0.0.0        192.0.2.1                0             0 65333 65333 i
*> 101.0.0.0        192.0.2.1                0             0 65333 65333 i
*> 102.0.0.0        192.0.2.1                0             0 65333 65333 i
*> 103.0.0.0        192.0.2.1                0             0 65333 65333 i
*> 104.0.0.0        192.0.2.1                0             0 65333 65333 i
*> 105.0.0.0        192.0.2.1                0             0 65333 65333 i
*> 106.0.0.0        192.0.2.1                0             0 65333 65333 i
*> 169.254.0.0      192.0.2.1                0             0 65333 65333 i
*> 172.16.0.0/12    192.0.2.1                0             0 65333 65333 i
*> 176.0.0.0/8      192.0.2.1                0             0 65333 65333 i
*> 177.0.0.0/8      192.0.2.1                0             0 65333 65333 i
*> 179.0.0.0/8      192.0.2.1                0             0 65333 65333 i
*> 181.0.0.0/8      192.0.2.1                0             0 65333 65333 i
*> 185.0.0.0/8      192.0.2.1                0             0 65333 65333 i

List routes that are currently installed in the routing table that were learned by BGP .

(root) # get router info routing-table bgp
B       5.0.0.0/8 [20/0] via 192.0.2.1 (recursive is directly connected, unknown), 00:00:19
B       14.0.0.0/8 [20/0] via 192.0.2.1 (recursive is directly connected, unknown), 00:00:19
B       23.0.0.0/8 [20/0] via 192.0.2.1 (recursive is directly connected, unknown), 00:00:19
B       31.0.0.0/8 [20/0] via 192.0.2.1 (recursive is directly connected, unknown), 00:00:19
B       36.0.0.0/8 [20/0] via 192.0.2.1 (recursive is directly connected, unknown), 00:00:19
B       37.0.0.0/8 [20/0] via 192.0.2.1 (recursive is directly connected, unknown), 00:00:19
B       39.0.0.0/8 [20/0] via 192.0.2.1 (recursive is directly connected, unknown), 00:00:19
B       42.0.0.0/8 [20/0] via 192.0.2.1 (recursive is directly connected, unknown), 00:00:19

After all is configured and saved (and probably doesn’t work) comes the bgp debug round.
Enable bgp debug on the appliance

#diag ip router bgp all enable

Enable debug output to console

diag debug enable

To stop this output

diagnose debug disable

To verify that debug is on

# diag ip router bgp show
BGP debugging status:
  BGP events debugging is on
  BGP debug level: INFO

If nothing after that happens try clearing all BGP sessions

#exec router clear bgp all

The good way to judge something new is to compare it with something you already know. To continue
With that logic I cross-reference debug output seen on Fortigate with the one seen on the Cisco BGP peer. That
way you can decide what is more informative and who wins the race (Cisco of course, what you thought?).

Case 1
One of the peers is configured with wrong AS number.
In Fortigate you see this:

BGP: 84.22.96.5-Outgoing [FSM] State: Idle Event: 3
BGP: 84.22.96.5-Outgoing [NETWORK] FD=15, Sock Status: 0-Success
BGP: 84.22.96.5-Outgoing [FSM] State: Connect Event: 17
BGP: 84.22.96.5-Outgoing [ENCODE] Msg-Hdr: Type 1
BGP: 84.22.96.5-Outgoing [ENCODE] Open: Ver 4 MyAS 65002 Holdtime 180
BGP: 84.22.96.5-Outgoing [ENCODE] Open: Msg-Size 45
BGP: 84.22.96.5-Outgoing [DECODE] Msg-Hdr: type 3, length 23
BGP: %BGP-3-NOTIFICATION: received from 84.22.96.5 2/2 (OPEN Message Error/Bad Peer AS.) 2 data-bytes

Now let’s compare to the debug from Cisco

#debug ip bgp events
Mar 24 13:14:55.572: %BGP-3-NOTIFICATION: sent to neighbor 10.250.250.2 2/2 (peer in wrong AS) 2 bytes FDEA FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF 002D 0104 FAEA 01B4 0AFA EA02 1302 0201 1400 0100 0132 0222 0012 0222 00

Case 2
MD5 authentication is set on Cisco but not on the Fortigate. Again for comparison
debug from Fortigate and debug from Cisco
Cisco:

Jan  5 10:42:14.299: %TCP-6-BADAUTH: No MD5 digest from 10.250.250.2 (1037) to 84.22.96.5(179)

Fortigate:

84.22.96.5-Outgoing [FSM] State: Connect Event: 9
BGP: [RIB] Scanning BGP Network Routes...
84.22.96.5-Outgoing [FSM] State: Connect Event: 9
BGP: [RIB] Scanning BGP Network Routes...

Case 3 (that actually happened when I configured this Fortigate) is mismatched MD5 password on either side

Fortigate:
Doing summary listing showed peering as down :

84.22.96.5   4  65333     934    1036        0    0    0    never Connect

Cisco:

*Mar 24 13:40:28.800: BGP: Regular scanner event timer
*Mar 24 13:40:28.800: BGP: Import timer expired. Walking from 1 to 1
*Mar 24 13:40:42.764: %TCP-6-BADAUTH: Invalid MD5 digest from 10.250.250.2(11064) to 84.22.96.5(179)

Case 4 On Cisco ttl-security is enabled while on Forigate ebgp multi-hop is not .
There is no such thing as TTL security on the Fortigate by the way, all you can do to handle this state is enable ebgp-multihop and them it starts sending BGP packets with ttl = 255 .

Cisco:

Jan  7 13:01:36.992: %BGP-4-INCORRECT_TTL: Discarded message with TTL 2 from 10.250.250.2

Forigate:

BGP: 84.22.96.5-Outgoing [FSM] State: OpenConfirm Event: 11
BGP: 84.22.96.5-Outgoing [ENCODE] Msg-Hdr: Type 4
BGP: 84.22.96.5-Outgoing [ENCODE] Keepalive: 13548 KAlive msg(s) sent
84.22.96.5-Outgoing [FSM] State: OpenConfirm Event: 10
BGP: 84.22.96.5-Outgoing [ENCODE] Msg-Hdr: Type 3
BGP: %BGP-3-NOTIFICATION: sending to 84.22.96.5 4/0 (Hold Timer Expired/Unspecified Error Subcode) 0 data-bytes
BGP: 84.22.96.5-Outgoing [FSM] State: Idle Event: 3
BGP: 84.22.96.5-Outgoing [NETWORK] FD=14, Sock Status: 111-Connection refused
BGP: 84.22.96.5-Outgoing [FSM] State: Connect Event: 18

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