Resolución de Problemas de Encabezado L2 Incorrecto para el Tráfico MPLS de Tránsito
Introducción
Este documento describe cómo resolver problemas cuando la trayectoria de reenvío MPLS se rompe debido a la corrupción del encabezado L2 en el nodo NCS4K (6.5.26).
Problema
En esta situación, el túnel de ingeniería de tráfico (TE) está activo, pero el ping de conmutación de etiquetas multiprotocolo (MPLS) no funciona a través del túnel MPLS:
tunnel-te5180 10.38.101.62 Up Up default
#ping mpls traffic-eng tunnel-te 5180
Thu Jan 5 21:30:29.245 UTC
Sending 5, 100-byte MPLS Echos to tunnel-te5180,
timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
.....
Success rate is 0 percent (0/5)Verá algunos saltos en el traceroute MPLS:
#traceroute mpls traffic-eng tunnel-te 5180
Thu Jan 5 21:30:49.405 UTC
Tracing MPLS TE Label Switched Path on tunnel-te5180, timeout is 2 seconds
Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 172.16.61.78 MRU 9582 [Labels: 27769 Exp: 0]
L 1 172.16.61.79 MRU 9582 [Labels: 28136 Exp: 0] 7 ms
. 2 *
. 3 *
. 4 *
. 5 *^CCuando verifica el túnel MPLS, observa que se señalizan dos saltos más para el router explícito (ERO):
#show mpls traffic-eng tunnels 5180
Thu Jan 5 21:31:11.958 UTC
Name: tunnel-te5180 Destination: 10.38.96.1 Ifhandle:0x80002c4
Signalled-Name: MIVLPAMI-0112003A_t5180
Status:
Admin: up Oper: up Path: valid Signalling: connected
path option 10, type dynamic (Basis for Setup, path weight 3000)
Accumulative metrics: TE 3000 IGP 30 Delay 900000
Path-option attribute: eline-any
Number of affinity constraints: 1
Include bit map : 0x2
Include ext bit map :
Length: 256 bits
Value : 0x::2
Include affinity name : eline(1)
G-PID: 0x0800 (derived from egress interface properties)
Bandwidth Requested: 7 kbps CT0
Creation Time: Thu Nov 10 22:17:55 2022 (7w6d ago)
Config Parameters:
Bandwidth: 0 kbps (CT0) Priority: 5 5 Affinity: 0x0/0xffff
Metric Type: TE (interface)
Path Selection:
Tiebreaker: Min-fill (default)
Hop-limit: disabled
Cost-limit: disabled
Delay-limit: disabled
Path-invalidation timeout: 10000 msec (default), Action: Tear (default)
AutoRoute: enabled LockDown: disabled Policy class: not set
Forward class: 0 (not enabled)
Forwarding-Adjacency: disabled
Autoroute Destinations: 0
Loadshare: 0 equal loadshares
Auto-bw: enabled
Last BW Applied: 7 kbps CT0 BW Applications: 29
Last Application Trigger: Periodic Application
Bandwidth Min/Max: 0-4294967295 kbps
Application Frequency: 60 min Jitter: 0s Time Left: 46m 48s
Collection Frequency: 5 min
Samples Collected: 2 Next: 1m 3s
Highest BW: 0 kbps Underflow BW: 0 kbps
Adjustment Threshold: 10% 10 kbps
Overflow Detection disabled
Underflow Detection disabled
Resignal Last-bandwidth Disabled
Auto-Capacity: Disabled:
Fast Reroute: Enabled, Protection Desired: Any
Path Protection: Not Enabled
BFD Fast Detection: Disabled
Reoptimization after affinity failure: Enabled
Soft Preemption: Disabled
History:
Tunnel has been up for: 7w6d (since Thu Nov 10 22:17:55 UTC 2022)
Current LSP:
Uptime: 15:09:12 (since Thu Jan 05 06:22:00 UTC 2023)
Reopt. LSP:
Last Failure:
LSP not signalled, identical to the [CURRENT] LSP
Date/Time: Thu Jan 05 19:03:33 UTC 2023 [02:27:39 ago]
Prior LSP:
ID: 32 Path Option: 10
Removal Trigger: reoptimization completed
Path info (IS-IS 1 level-2):
Node hop count: 3
Hop0: 172.16.61.79
Hop1: 172.16.57.244
Hop2: 172.16.6.59
Hop3: 10.38.96.1Al ir al primer salto a lo largo de la trayectoria, verá la entrada correcta de la Base de información de reenvío de etiquetas MPLS (LFIB) para este túnel:
#show mpls forwarding labels 27769
Fri Jan 6 06:13:04.220 UTC
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
27769 28136 TE: 5180 Hu0/10/0/11/2.4001 172.16.57.244 0
28136 TE: 5180 tt60409 point2point 0 (!)
La interfaz de salida en este nodo utiliza esta dirección MAC, por lo que esta se puede utilizar como MAC de origen (SRC) en el encabezado L2 para las tramas L2:
#show interfaces hundredGigE 0/10/0/11/2.4001
Fri Jan 6 06:14:45.773 UTC
HundredGigE0/10/0/11/2.4001 is up, line protocol is up
Interface state transitions: 79
Hardware is VLAN sub-interface(s), address is 0c11.67c8.2041
Description: To HundredGigE1/3/0/10/2.PHLAPALO-12121302A:CID:I1001/GE100/PHLAPALO/SLTNPAST
Internet address is 172.16.57.245
MTU 9600 bytes, BW 100000000 Kbit (Max: 100000000 Kbit)
reliability 255/255, txload 0/255, rxload 0/255
Encapsulation 802.1Q Virtual LAN, VLAN Id 4001, loopback not set,
Last link flapped 1w6d
ARP type ARPA, ARP timeout 04:00:00
Last input 00:00:00, output 00:00:00
Last clearing of "show interface" counters never
5 minute input rate 64000 bits/sec, 62 packets/sec
5 minute output rate 2198000 bits/sec, 699 packets/sec
4529877895 packets input, 2267795435148 bytes, 6 total input drops
0 drops for unrecognized upper-level protocol
Received 124 broadcast packets, 0 multicast packets
3926978895 packets output, 1611587340639 bytes, 0 total output drops
Output 0 broadcast packets, 0 multicast packetsPero en el lado vecino en show capture packets ingress location <active LC VM>, verá la etiqueta MPLS correcta, pero las direcciones MAC de destino (DST) y SRC de L2 son totalmente incorrectas:
[200] Jan 6 06:10:12.449, len: 103, hits: 1, buffhdr type: 1
i/p i/f: HundredGigE1/3/0/10/2
punt reason: DROP_PACKET
Ingress Headers:
port_ifh: 0x8001ae4, sub_ifh: 0x0, bundle_ifh: 0x0
logical_port: 0x6c1, pd_pkt_type: 3
punt_reason: DROP_PACKET (0)
payload_offset: 21, l3_offset: 21
FTMH:
pkt_size: 0x7e, tc: 0, tm_act_type: 0, ssp: 0x981
PPH:
pph_fwd_code: CPU Trap (7), fwd_hdr_offset: 0
inlif: 0x0, vrf: 0x0, rif: 0x0
FHEI:
trap_code: Rx_UNKNOWN_PACKET (63), trap_qual: 193
[ether dst: 0000.0000.0000 src: 0c11.67c8.2000 type/len: 0x8847]
[MPLS label: 28136, exp 0x6, eos 0, ttl 255] La dirección MAC de DST es all-0 y la dirección MAC de SRC coincide con la interfaz de administración del nodo NCS4K:
#show interfaces mgmtEth 0/rp1/emS/0
Fri Jan 6 06:15:59.141 UTC
MgmtEth0/RP1/EMS/0 is down, line protocol is down
Interface state transitions: 0
Hardware is Management Ethernet, address is 0c11.67c8.2000 (bia 0c11.67c8.2000)
Internet address is 10.230.192.86
MTU 1514 bytes, BW 100000 Kbit (Max: 100000 Kbit)
reliability 255/255, txload 0/255, rxload 0/255
Encapsulation ARPA,
Full-duplex, 100Mb/s, unknown, link type is autonegotiation
loopback not set,
ARP type ARPA, ARP timeout 04:00:00
Last input never, output never
Last clearing of "show interface" counters never
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 total input drops
0 drops for unrecognized upper-level protocol
Received 0 broadcast packets, 0 multicast packets
0 runts, 0 giants, 0 throttles, 0 parity
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 total output drops
Output 0 broadcast packets, 0 multicast packets
0 output errors, 0 underruns, 0 applique, 0 resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitionsSolución
La causa raíz es este DDTS - ID de bug de Cisco CSCvz99253 
ID de bug de Cisco CSCwa11748 duplicado del ID de bug de Cisco CSCvz99253 que se corrige en la versión 6.5.32:
++++++++
Dec 23 23:24:58.214 ofa_ipnhgroup_event 0/LC1 3235382# t4839 TP3147224,dnxsdk_l3_fec_create,enter,trans_id,357633649,npu_id,0,is_modify,1,use_eei_encoding,0,dest,0x6052,encap_id,0x4000304a,fec_id,0x2001fe98,
Dec 23 15:10:16.787 ofa_ipnh_event 0/LC1 210586# t5614 TP2061,client_ipnh_create,grid_res_id_alloc_req_success,trans_id,357386085,encap_id,0x304a,alloc_sz,2
Dec 23 15:10:16.787 ofa_ipnh_event 0/LC1 286920# t4857 TP9909,dispatch_ipnh,resolve_refhdl_success,ref_l3intf_trans_id,357386081,hdl,0x87a75238
Dec 23 15:10:16.787 ofa_ipnh_event 0/LC1 172418# t4857 TP9913,dummy_block,trans_id,357386085,wait,duration,time,0.1742
Dec 23 15:10:16.787 ofa_ipnh_event 0/LC1 153352# t4857 TP3149344,srv_ipnh_create,entry,trans_id,357386085,npu_mask,0x100000,l3a_mac_addr,00af.1f18.0043,l3a_intf_id,28,port_id,0
Dec 23 15:10:16.780 ofa_ipnh_event 0/LC1 258284# t5614 TP2061,client_ipnh_create,grid_res_id_alloc_req_success,trans_id,357386077,encap_id,0x3048,alloc_sz,2
Dec 23 15:10:16.780 ofa_ipnh_event 0/LC1 105614# t4857 TP9909,dispatch_ipnh,resolve_refhdl_success,ref_l3intf_trans_id,357383451,hdl,0x87a75238
Dec 23 15:10:16.780 ofa_ipnh_event 0/LC1 172408# t4857 TP9913,dummy_block,trans_id,357386077,wait,duration,time,0.1947
Dec 23 15:10:16.780 ofa_ipnh_event 0/LC1 286912# t4857 TP3149344,srv_ipnh_create,entry,trans_id,357386077,npu_mask,0x100000,l3a_mac_addr,00af.1f18.0043,l3a_intf_id,28,port_id,0
++++++++Como método de recuperación, puede volver a configurar la subinterfaz de salida afectada.
Historial de revisiones
| Revisión | Fecha de publicación | Comentarios |
|---|---|---|
1.0 |
09-Feb-2023
|
Versión inicial |
Comentarios