Description
This article explains how to verify the routes/prefix received from the BGP Peer using Debugs.
Scope
FortiGate.
Solution
Topology:
Hub: Router ID- 192.168.2.110.
Spoke_1: Router ID – 192.168.2.121.
Prefix Advertised: – 121.121.10.0/24, 121.121.20.0/24, 121.121.30.0/24.
Steps to follow:
Debugs will be run on the HUB FortiGate to confirm the prefix received from Spoke_1 Peer:
diagnose ip router bgp all enable
diagnose ip router bgp level info
diagnose debug console timestamp enable
diagnose debug enable
Note:
Starting from v7.2.0+, it is possible to collect BGP debugs for a specific neighbor by using the filter command: 'diagnose ip router bgp set-filter neighbor <neighbor address>'.
Follow this KB article for more details: Technical Tip: Capture BGP debugs for a specific neighbor.
It is possible to use the command to do a soft reset of the Incoming routes:
execute router clear bgp all soft in
Output:
2022-11-15 18:50:42 BGP: 192.168.2.121-Outgoing [FSM] State: OpenConfirm Event: 26
2022-11-15 18:50:42 id=20300 msg="BGP: %BGP-5-ADJCHANGE: VRF 0 neighbor 192.168.2.121 Up <----- Peers are UP confirmation.
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [FSM] State: Established Event: 34
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [ENCODE] Msg-Hdr: Type 2
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [ENCODE] Update: Msg #1 Size 23
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [DECODE] Msg-Hdr: type 2, length 56
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [DECODE] Update: Starting UPDATE decoding... Bytes To Read (60), msg_size (37)
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [DECODE] Update: NLRI Len(12)
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [DECODE] Msg-Hdr: type 2, length 23
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [DECODE] Update: Starting UPDATE decoding... Bytes To Read (4), msg_size (4)
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [FSM] State: Established Event: 27
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [RIB] Update: Received Prefix 121.121.10.0/24 path_id 0 <----- Prefix received.
2022-11-15 18:50:43 BGP: [NSM] Verified NH 192.168.2.121 with NSM
2022-11-15 18:50:43 BGP: VRF 0 NSM announce: 121.121.10.0/24
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [RIB] Update: Received Prefix 121.121.30.0/24 path_id 0 <----- Prefix received.
2022-11-15 18:50:43 BGP: VRF 0 NSM announce: 121.121.30.0/24
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [RIB] Update: Received Prefix 121.121.20.0/24 path_id 0 <----- Prefix received.
2022-11-15 18:50:43 BGP: VRF 0 NSM announce: 121.121.20.0/24
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [FSM] Update: IPv4 Unicast End-Of-Rib Marker Received <----- End-of-RIB Marker MUST be sent by a BGP speaker to its peer once it completes the initial routing update.
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [FSM] Process End-of-RIB: Received for afi/safi: 1/1
2022-11-15 18:50:43 BGP: 192.168.2.121-Outgoing [FSM] State: Established Event: 27
Check the BGP routing table on HUB:
HUB # get router info routing-table bgp
Routing table for VRF=0
B 121.121.10.0/24 [200/0] via 192.168.2.121 (recursive is directly connected, port1), 00:08:02, [1/0]
B 121.121.20.0/24 [200/0] via 192.168.2.121 (recursive is directly connected, port1), 00:08:02, [1/0]
B 121.121.30.0/24 [200/0] via 192.168.2.121 (recursive is directly connected, port1), 00:08:02, [1/0]
CLI command to view received routes from a specific neighbor:
get router info bgp neighbors <neighbor IP> received-routes
Note.
If an error shows up after running 'get router info bgp neighbors <neighbor IP> received-route', then enable the 'set soft-reconfiguration enable' command under the BGP neighbor.
get router info bgp neighbors <neighbor IP> routes
Command 'get router info bgp neighbors <neighbor IP> routes' shows only filtered(in) received routes.
The command 'get router info bgp neighbors' shows details of the neighbors, including: Peer IP address, router ID, remote AS, BGP state, and the negotiated capabilities.
Related articles:
Technical Tip: BGP Neighbor Adjacency States
Technical Tip: How to check BGP advertised and received routes on a FortiGate
