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Monitoring MPLS on CiscoIOS Platforms
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Outline
Overview
Monitoring MPLS
Monitoring LDP
Monitoring Label Switching
Debugging MPLS and LDP
Lesson Summary
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show mpls ldp parameters
Router#
Displays LDP parameters on the local router.
MPLS Monitoring Commands
show mpls interfaces
Router#
Displays MPLS status on individual interfaces.
show mpls ldp discovery
Router#
Displays all discovered LDP neighbors.
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MPLS Monitoring Commands:
show mpls ldp parameters
Protocol version: 1
Downstream label pool: min label: 16; max label:
100000
[Configured: min label: 1000; max label: 1999]
Session hold time: 180 sec; keep alive interval: 60sec
Discovery hello: holdtime: 15 sec; interval: 5 sec
Discovery targeted hello: holdtime: 180 sec; interval:
5 sec
Downstream on Demand max hop count: 255TDP for targeted sessions
LDP initial/maximum backoff: 15/120 sec
LDP loop detection: off
Router#show mpls ldp parameters
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MPLS Monitoring Commands:
show mpls interfaces
Router#show mpls interfaces [interface] [detail]
Interface Serial0/0:IP labeling enabled (ldp)
LSP Tunnel labeling enabled
Tag Frame Relay Transport tagging not enabled
Tagging operational
Fast Switching Vectors:
IP to MPLS Fast Switching Vector
MPLS Turbo Vector
MTU = 1500
Interface Serial0/3:
IP labeling enabled (ldp)
LSP Tunnel labeling not enabled
Tag Frame Relay Transport tagging not enabled
Tagging operationalFast Switching Vectors:
IP to MPLS Fast Feature Switching Vector
MPLS Feature Vector
MTU = 1500
Router#show mpls interfaces [interface] [detail]
IP labeling enabled (ldp)
IP labeling enabled (ldp)
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MPLS Monitoring Commands:
show mpls ldp discovery
Router#show mpls ldp discoveryLocal LDP Identifier:
192.168.3.102:0
Discovery Sources:
Interfaces:
Serial1/0.1(ldp): xmit/recv
LDP Id: 192.168.3.101:0
Serial1/0.2(ldp): xmit/recv
LDP Id: 192.168.3.100:0
show mpls ldp discovery
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show mpls ldp neighbor
Router#
Displays individual LDP neighbors.
LDP Monitoring Commands
show mpls ldp neighbor detail
Router#
Displays more details about LDP neighbors.
show mpls ldp bindings
Router#
Displays label information base (LIB). show mpls ldp bindings [network{mask| length} [longer-prefixes]]
[local-label label [-label]} [remote-label label[- label] [neighboraddress] [local]
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LDP Monitoring Commands:
show mpls ldp neighbor detail
Router#show mpls ldp neighbor detail
Peer LDP Ident: 192.168.3.100:0; Local LDP Ident 192.168.3.102:0
TCP connection: 192.168.3.100.646 192.168.3.102.11000
State: Oper; Msgs sent/rcvd: 3117/3112; Downstream;
Last TIB rev sent2
Up time: 2w4d; UID: 4; Peer Id 0;
LDP discovery sources:Serial0/0; Src IP addr: 130.0.0.2
holdtime: 15000 ms, hello interval: 5000 ms
Addresses bound to peer LDP Ident:
192.168.3.10 192.168.3.14 192.168.3.100
Peer holdtime: 180000 ms; KA interval: 60000 ms; Peerstate: estab
show mpls ldp neighbor detail
State: Oper;
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Router#show mpls ldp bindings
10.102.0.0/16, rev 29
local binding: label: 26
remote binding: lsr: 172.27.32.29:0, label: 26
10.211.0.7/32, rev 32local binding: label: 27
remote binding: lsr: 172.27.32.29:0, label: 28
10.220.0.7/32, rev 33
local binding: label: 28
remote binding: lsr: 172.27.32.29:0, label: 29
LDP Monitoring Commands:
show mpls ldp bindings
show mpls ldp bindings
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show mpls forwarding-table
Router#
Displays contents of LFIB.
Monitoring Label Switching
show ip cef detail
Router#
Displays label or labels attached to a packet duringlabel imposition on edge LSR.
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Monitoring Label Switching:
show mpls forwarding-table
Router#show mpls forwarding-table ? A.B.C.D Destination prefix
detail Detailed information
interface Match outgoing interface
labels Match label values
lsp-tunnel LSP Tunnel idnext-hop Match next hop neighbor
vrf Show entries for a VPN
Routing/Forwarding instance
| Output modifiers
show mpls forwarding-table ?
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Monitoring Label Switching:
show mpls forwarding-table detail
Router#show mpls forwarding-table detail
Local Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface
70 Pop tag 192.168.3.3/32 0 Se0/0 point2point
MAC/Encaps=4/4, MTU=1504, Tag Stack{}
0F008847
No output feature configured
Per-packet load-sharing71 Pop tag 192.168.3.4/32 0 Se0/0 point2point
MAC/Encaps=4/4, MTU=1504, Tag Stack{}
0F008847
No output feature configured
Per-packet load-sharing
show mpls forwarding-table detail
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Monitoring Label Switching:
show ip cef detail
Router#show ip cef 192.168.20.0 detail192.168.20.0/24, version 23, cached adjacency to Serial1/0.2
0 packets, 0 bytes
tag information set
local tag: 33
tag rewrite with Se1/0.2, point2point, tags imposed: {32}
via 192.168.3.10, Serial1/0.2, 0 dependenciesnext hop 192.168.3.10, Serial1/0.2
valid adjacency
tag rewrite with Se1/0.2, point2point, tags imposed: {32}
show ip cef 192.168.20.0 detail
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debug mpls ldp ...
Router#
Debugs TDP adjacencies, session establishment,and label bindings exchange.
Debugging MPLS and LDP
debug mpls lfib
Router#
Debugs LFIB events: label creations, removals,rewrite, and so on.
debug mpls packets [ interface ]Router#
Debugs labeled packets switched by the router.
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Summary
The show mpls interfaces command will show only
those interfaces that have had mpls enabled. Use the showmpls ldp bindings command to display
the LIB table.
Use the showmpls forwarding-table command todisplay the LFIB table.
Use the debug mpls packetscommand with carebecause it causes fast and distributed switching to
be disabled.
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Troubleshooting MPLS onCisco IOS Platforms
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Outline
Overview
What are Common Frame-Mode MPLS Issues? Solving LDP Session Startup Issues
Solving Label Allocation Issues
Solving Label Distribution Issues
Solving Packet Labeling Issues
Solving Intermittent MPLS Failures After Interface
Failure
Solving Packet Propagation Issues
Lesson Summary
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Symptoms of Common Frame-Mode MPLSIssues
The LDP session does not start.
Labels are not allocated. Labels are not distributed.
Packets are not labeled, although the labels have
been distributed. MPLS intermittently breaks after an interface
failure.
Large packets are not propagated across thenetwork.
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LDP Session Startup Issues
Symptom
LDP neighbors are not discovered. The show mpls ldp discovery command does
not display expected LDP neighbors.
DiagnosisMPLS is not enabled on the adjacent router.
Verification
Verify with the show mpls interface command onthe adjacent router.
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LDP Session Startup Issues (Cont.)
Symptom
LDP neighbors are not discovered. Diagnosis
There is a label distribution protocol mismatch
TDP on one end, LDP on the other end. Verification
Verify with the show mpls interface detail
command on both routers.
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LDP Session Startup Issues (Cont.)
Symptom
LDP neighbors are not discovered. Diagnosis
Packet filter drops LDP neighbor discovery
packets. Verification
Verify access list presence with the show ip
interface command.Verify access list contents with the show access-
list command.
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LDP Session Startup Issues (Cont.)
Symptom
LDP neighbors are discovered; the LDP sessionis not established.
The show mpls ldp neighbor command does notdisplay a neighbor in operational state.
Diagnosis
The connectivity between loopback interfaces isbroken; the LDP session is usually establishedbetween loopback interfaces of adjacent LSRs.
Verification
Verify connectivity with the extended pingcommand.
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Label Allocation Issues
Symptom
Labels are not allocated for local routes. The show mpls forwarding-table command does
not display any labels.
Diagnosis
CEF is not enabled.
Verification
Verify with the show ip cef command.
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Intermittent MPLS Failures After InterfaceFailure
Symptom
The overall MPLS connectivity in a routerintermittently breaks after an interface failure.
Diagnosis
The IP address of a physical interface is used forthe LDP (or TDP) identifier. Configure a loopbackinterface on the router.
Verification
Verify the local LDP identifier with the show mplsldp neighbors command.
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Packet Propagation Issues
Symptom
Large packets are not propagated across the network.
Use of the extended ping command with varying packetsizes fails for packet sizes close to 1500
In some cases, MPLS might work, but MPLS VPN will fail.
DiagnosisThere are label MTU issues or switches that do not support
jumbo frames in the forwarding path.
Verification
Issue the traceroute command through the forwarding path;identify all LAN segments in the path.
Verify the label MTU setting on routers attached to LANsegments.
Check for low-end switches in the transit path.
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Summary
Some common frame-mode issues are as follows: LDP sessiondoes not start, labels are not allocated or distributed, and MPLS
intermittently breaks after an interface failure. One LDP session startup issue is when LSP neighbors are not
discovered.
A label allocation issue is one where the labels are not allocated
for local routes. Labels may be allocated, but not distributed correctly.
Ensure that there are no conflicts between CEF and any otherconfigured features; otherwise, packets might not be labeled.
Use loopback IP addresses, not a configured interface IPaddress, to avoid MPLS connectivity to intermittently breakdown.
Large packets are not propagated across the network.