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Description

With graceful-restart disable, for routes learned from iBGP/eBGP peer(s), "show bgp summary" and "show bgp neigbhor" output might see incomplete Active/Received/Accepted counters than peer advertised after bgp neighbor flapped.

This issue might be seen if the following conditions are met:
* The graceful-restart helper mode is disabled explicitly using config
* The damping is not enabled

Symptoms

<<<< example output >>>>
ebgp neighbor advertising 1M route prefix. In this case, issued router shown "940018" routes in CLI outpout after this neighbor session flapped. (not 100% recurrence rate)

labroot@r02_re> show configuration protocols bgp
path-selection always-compare-med;
group GROUP1 {
type external;
local-address 192.168.1.105;
minimum-hold-time 30;
family inet {
unicast;
}
export [ XXXXX ];
remove-private;
peer-as 612345;
multipath;
neighbor 192.168.1.106;
}
group IBGP-V4 {
type internal;
local-address 192.168.13.253;
import YYYYY;
family inet {
unicast {
add-path {
receive;
}
}
}
export [ XXXXX ];
peer-as 654321;
neighbor 192.168.219.250 {
multipath;
}
neighbor 192.168.221.251 {
multipath;
}
}
precision-timers;
accept-remote-nexthop;
hold-time 180;
advertise-inactive;
log-updown;
bgp-error-tolerance;
graceful-restart {
disable;
}

< show bgp summary >
---(refreshed at 2024-10-23 10:29:06 JST)---
Threading mode: BGP I/O
Groups: 3 Peers: 5 Down peers: 0
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0
15227689 15133813 0 0 0 0
inet6.0
12 6 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
192.168.1.106 612345 1009 4 0 16 1:12 Establ
inet.0: 940018/940018/940018/0 <<<<<<<<<<<<<<< expected 1000000
192.168.219.250 654321 411 1285 1477 12 7:07 Establ
inet.0: 57/33011/33011/0
192.168.221.251 654321 14 46 920080 1 2:42 Establ
inet.0: 0/0/0/0
---(refreshed at 2024-10-23 10:29:11 JST)---
Threading mode: BGP I/O
Groups: 3 Peers: 5 Down peers: 0
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0
15227689 15133813 0 0 0 0
inet6.0
12 6 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
192.168.1.106 612345 1009 4 0 16 1:17 Establ
inet.0: 940018/940018/940018/0 <<<<<<<<<<<<<<< expected 1000000
192.168.219.250 654321 411 1315 0 12 7:12 Establ
inet.0: 57/33011/33011/0
192.168.221.251 654321 14 46 920080 1 2:47 Establ
inet.0: 0/0/0/0
---(refreshed at 2024-10-23 10:29:16 JST)---
Threading mode: BGP I/O
Groups: 3 Peers: 5 Down peers: 0
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0
15227690 15133814 0 0 0 0
inet6.0
12 6 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
192.168.1.106 612345 1010 5 0 16 1:22 Establ
inet.0: 940018/940018/940018/0 <<<<<<<<<<<<<<< expected 1000000
192.168.219.250 654321 412 1315 0 12 7:17 Establ
inet.0: 58/33012/33012/0
192.168.221.251 654321 14 46 920080 1 2:52 Establ
inet.0: 0/0/0/0

< show bgp neighbor 192.168.1.106 >
{master}
labroot@r02_re> show bgp neighbor 192.168.1.106
Oct 23 10:30:38
Peer: 192.168.1.106+60700 AS 612345 Local: 192.168.1.105+179 AS 654321
Description: GROUP1
Group: GROUP1 Routing-Instance: master
Forwarding routing-instance: master
Type: External State: Established Flags: <Sync RSync>
Last State: EstabSync Last Event: RecvKeepAlive
Last Error: Cease
Export: [ XXXX ALL-REJECT ]
Options: <Preference LocalAddress HoldTime AdvertiseInactive RemovePrivateAS LogUpDown AddressFamily PeerAS Multipath Refresh>
Options: <MinHoldTime AcceptRemoteNextHop>
Options: <GracefulRestartHelperDisabled LLGRHelperDisabled GracefulShutdownRcv>
Address families configured: inet-unicast
Local Address: 192.168.1.105 Holdtime: 180 Preference: 170
Graceful Shutdown Receiver local-preference: 0
Number of flaps: 16
Last flap event: Stop
Error: 'Cease' Sent: 15 Recv: 0
Malformed attributes log interval: 300 route limit: 1000
Peer ID: xxx.xxx.xxx.xxx Local ID: 192.168.13.253 Active Holdtime: 90
Keepalive Interval: 30 Group index: 0 Peer index: 0 SNMP index: 0
I/O Session Thread: bgpio-0 State: Enabled
BFD: disabled, down
Local Interface: ae54.0
NLRI advertised by peer: inet-unicast
NLRI for this session: inet-unicast
Peer supports Refresh capability (2)
Peer does not support Restarter functionality
Restart flag received from the peer: Notification
Peer does not support LLGR Restarter functionality
Peer supports 4 byte AS extension (peer-as 612345)
Peer does not support Addpath
NLRI(s) enabled for color nexthop resolution: inet-unicast
Table inet.0 Bit: 20000
RIB State: BGP restart is complete
Send state: in sync
Active prefixes: 940018 <<<<<<<<<<<<<<< expected 1000000
Received prefixes: 940018 <<<<<<<<<<<<<<< expected 1000000
Accepted prefixes: 940018 <<<<<<<<<<<<<<< expected 1000000
Suppressed due to damping: 0
Advertised prefixes: 1
Last traffic (seconds): Received 3 Sent 3 Checked 164
Input messages: Total 1013 Updates 1005 Refreshes 0 Octets 4043411
Output messages: Total 9 Updates 1 Refreshes 0 Octets 210
Output Queue[1]: 0 (inet.0, inet-unicast)

{master}
labroot@r02_re>

labroot@r02_re> show route summary
Oct 23 10:41:04
Autonomous system number: 654321
Router ID: 192.168.1.105
Maximum ECMP: 32

inet.0: 1000163 destinations, 1124337 routes (1000163 active, 0 holddown, 0 hidden)
Direct: 6 routes, 6 active
Local: 4 routes, 4 active
OSPF: 55 routes, 54 active
BGP: 1124262 routes, 1000089 active
Static: 9 routes, 9 active
LDP: 1 routes, 1 active

inet.3: 13 destinations, 13 routes (13 active, 0 holddown, 0 hidden)
LDP: 13 routes, 13 active

mpls.0: 20 destinations, 20 routes (20 active, 0 holddown, 0 hidden)
MPLS: 6 routes, 6 active
LDP: 14 routes, 14 active

inet6.0: 73 destinations, 76 routes (73 active, 0 holddown, 0 hidden)
Direct: 7 routes, 7 active
Local: 6 routes, 6 active
OSPF3: 56 routes, 56 active
BGP: 6 routes, 3 active
INET6: 1 routes, 1 active

{master}
labroot@r02_re>

Solution

When bgp summary shown wrong number, you might get correct installing route number in FIB/RIB using following command example.

(Note, this is simple example. if you have multiple neighbors, it may not work)

< receiving prefix count from neighbor >
{master}
labroot@r02_re> show route receive-protocol bgp 192.168.1.106 | count
Oct 23 10:31:07
Count: 1000004 lines

< learned prefix count in FIB >
{master}
labroot@r02_re> show route forwarding-table all |match 192.168.1.106 | count
Count: 1000001 lines

Workaround
Do not disable the graceful restart helper mode.

Fixed by PR1558678

https://prsearch.juniper.net/problemreport/PR1558678

Modification History

2024-10-23 : Article Created