Customer reported that their MPLS LSP’s are bouncing and not stable. LSPs are going down only when LSPs are switching over to alternate path due to primary path failure
1. "show mpls lsp terse" displays LSP Down on Ingress MPLS Router
2. We logged in to the each router in the transit path and noticed below on Router_4
#We are not seeing RESV message from downstream neighbor connected via AE24 (Router_3)
labroot@Router_4> show rsvp session lsp name Router_1_To_Router_4 extensive
Nov 14 03:18:26
...
192.168.219.20
From: 192.168.189.20, LSPstate: Dn, ActiveRoute: 0
LSPname: Router_1_To_Router_4, LSPpath: Primary
Suggested label received: -, Suggested label sent: -
Recovery label received: -, Recovery label sent: -
Resv style: 0 -, Label in: -, Label out: -
Time left: 146, Since: Tue Nov 14 03:18:03 2023
Tspec: rate 0bps size 0bps peak Infbps m 20 M 9192
Port number: sender 29437 receiver 48728 protocol 0
Link protection desired
Soft preemption desired
Type: Protection down
PATH rcvfrom: 192.168.110.126 (ae7.0) 3 pkts
Adspec: received MTU 9170 sent MTU 9170
PATH sentto: 192.168.1.121 (ae24.0) 3 pkts
Explct route: 192.168.1.121 192.168.234.223 192.168.247.189
Record route: 192.168.188.200 192.168.251.222 192.168.94.171 192.168.110.126 <self> ...incomplete
Total 1 displayed, Up 0, Down 1
#No Active Reservation on interface AE24
labroot@Router_4> show rsvp interface
Nov 14 03:51:44
RSVP interface: 25 active
Active Subscr- Static Available Reserved Highwater
Interface State resv iption BW BW BW mark
ae0.0 Up 63 75% 50Gbps 37.4846Gbps 15.3913Mbps 42.442Mbps
ae12.0 Up 242 85% 800Gbps 679.905Gbps 94.6388Mbps 255.973Mbps
ae21.0 Up 0 85% 20Gbps 17Gbps 0bps 0bps
ae24.0 Up 0 70% 100Gbps 70Gbps 0bps 0bps
#No increments in the RESV message received on AE24.
labroot@Router_4> show rsvp interface ae24.0 detail
Nov 14 03:52:40
ae24.0 Index 333, State Ena/Up
NoAuthentication, Aggregate, NoReliable, LinkProtection
HelloInterval 9(second)
Address 96.34.1.120
ActiveResv 0, PreemptionCnt 0, Update threshold 10%
Subscription 70%, StaticBW 100Gbps, AvailableBW 70Gbps
ReservedBW [0] 0bps[1] 0bps[2] 0bps[3] 0bps[4] 0bps[5] 0bps[6] 0bps[7] 0bps
PacketType Total Last 5 seconds
Sent Received Sent Received
Path 715736 0 13 0
PathTear 224345 0 2 0
Resv 0 0 0 0
Hello 35278 155041 0 1
Ack 10 11 0 0
Srefresh 1 0 0 0
#RSVP neighbor cli outputs reports neighbor status as down. I see MX router is reporting “Remote instance: 0x0”.
labroot@Router_4> show rsvp neighbor detail
Nov 14 04:17:51
RSVP neighbor: 21 learned
Address: 192.168.1.121 via: ae24.0 status: Dead
Last changed time: 4d 21:04:32, Idle: 1:47:40 sec, Up cnt: 1, Down cnt: 1
Message received: 10
Hello: sent 35304, received: 22478, interval: 9 sec
Remote instance: 0x0, Local instance: 0xb384bc16
Refresh reduction: incomplete
Remote end: disabled, Ack-extension: enabled
#Tracelogs on Router_4. Path Message received from Upstream Router and is forwarding to downstream router via AE24
Nov 14 06:00:23.669596 RSVP recv Path 192.168.110.126->192.168.110.127 Len=276 ae7.0 - Session7 Len 16 192.168.219.63(port/tunnel ID 48728 Ext-ID 69.144.189.20) Proto 0
Nov 14 06:00:23.669614 RSVP send Ack 192.168.110.127->192.168.110.126 Len=20 ae7.0
Nov 14 06:00:23.669647 RSVP new Session 192.168.219.63(port/tunnel ID 48728 Ext-ID 192.168.189.20) Proto 0, session ID 376958
Nov 14 06:00:23.669672 RSVP new path state, session 192.168.219.63(port/tunnel ID 48728 Ext-ID 69.144.189.20) Proto 0
Nov 14 06:00:23.670361 Allocated Path message id 243927472 (epoch 15755287) for psb [PHOP Nbr: interface ae7.0, 192.168.110.126] [Session ID 376958, ID 537788212] (main)
Nov 14 06:00:23.670408 RSVP send Path 192.168.189.20->192.168.219.63 Len=276 ae24.0 - Session7 Len 16 192.168.219.63(port/tunnel ID 48728 Ext-ID 192.168.189.20) Proto 0
#Tracelogs on Router_3. Path Message received from Upstream Router_4 and is sending Ac/RESV back to Router_4
Nov 14 06:00:03.401231 RSVPIO recv Path 192.168.189.20->192.168.219.63 Len=276 ae2.0 - Session7 Len 16 192.168.219.63(port/tunnel ID 48728 Ext-ID 69.144.189.20) Proto 0 {rsvp-io}
Nov 14 06:00:03.401563 RSVPIO send Ack 192.168.1.121->192.168.1.120 Len=20 ae2.0 {rsvp-io}
Nov 14 06:00:03.402698 RSVPIO send Resv 192.168.1.121->192.168.1.120 Len=204 ae2.0 - Session7 Len 16 192.168.219.63(port/tunnel ID 48728 Ext-ID 192.168.189.20) Proto 0 {rsvp-io}
#Message Logs reports below on Router_3. AE2 connects to Router_4
Nov 15 13:32:53 2023 Router_3 rpd[8466]: RPD_RSVP_NBRDOWN: RSVP neighbor 192.168.1.120 down on interface ae2.0 nbr-type Direct, neighbor timeout
Nov 15 13:33:53 2023 Router_3 rpd[8466]: RPD_RSVP_NBRDOWN: RSVP neighbor 192.168.1.120 down on interface ae2.0 nbr-type Direct, neighbor timeout
Nov 15 13:34:53 2023 Router_3 rpd[8466]: RPD_RSVP_NBRDOWN: RSVP neighbor 192.168.1.120 down on interface ae2.0 nbr-type Direct, neighbor timeout
Nov 15 13:35:53 2023 Router_3 rpd[8466]: RPD_RSVP_NBRDOWN: RSVP neighbor 192.168.1.120 down on interface ae2.0 nbr-type Direct, neighbor timeout
The applied loopback filter on Router_4 is not configured to allow RSVP session via interface "ae24.0". Issue resolved after adding "AE24.0" IPv4 address to prefix list rsvp-addresses
Snippet of Incorrect loopback filter, which is causing LSP failures
Filter Name : protect-routing-engine
term 110 {
from {
source-prefix-list {
rsvp-addresses;
}
protocol rsvp;
then {
policer protect-routing-engine-policer;
count rsvp-count;
accept;
…
term 500 {
catch-all-addresses;
count catch-all-count;
log;
discard;
Prefix List : rsvp-addresses
prefix-list rsvp-addresses {
192.168.0.0/19;
192.168.1.0/24;
192.168.2.0/15;
192.168.3.0/16;
192.168.4.0/15;
192.168.5.0/16;
192.168.6.0/12;
192.168.7.0/16;
192.168.8.0/15;