frr8.4 MPLS decapsulation exception

[Sherry0808]

trafficstars

I have three devices with the following configurations: 172.16.19.1, 172.16.20.1, and 172.16.21.1. The terminal device 001 has an address of 192.168.103.1 and is directly connected to 172.16.21.1. The terminal device 002 has an address of 192.168.102.1 and is directly connected to 172.16.20.1. I am unable to access the terminal device with the address 192.168.103.1, which is connected to 172.16.21.1, from 192.168.102.1. Upon capturing packets on the interface of 172.16.21.1, I noticed an MPLS decapsulation exception. I have attached a screenshot of the packet capture. What could be the possible cause of this issue? Have any of you encountered a similar situation?

[eqvinox]

FRR only configures the routing tables for the kernel to work with, you are not showing any details on that. Please add the output of ip route list and ip -f mpls route list. If FRR installs MPLS label "routes" correctly, you'd need to look at the kernel code to figure out further details.

Also, a "MPLS decapsulation exception" sounds like you're looking at this in wireshark. You need to configure wireshark explicitly for the content of MPLS labeled packets, it cannot autodetect what the next protocol inside is. And whether the data inside is somehow wrong or not has nothing to do with FRR or the local system…

[Sherry0808]

What are the troubleshooting ideas? In what order should I check whether it is the MPLS configuration problem of FRR or the kernel problem?

[donaldsharp]

@Sherry0808 -> Eqvinox gave you a starting place for us to help. I'm not sure what else we can do until you provide us the data asked for

[Sherry0808]

Building configuration...

Current configuration: ! frr version 8.4.2 frr defaults traditional log syslog informational no ipv6 forwarding ! interface eno1.902 ip address 10.1.0.6/30 exit ! interface eno1.904 ip address 10.1.0.9/30 exit ! interface eno1.906 ip address 10.1.0.14/30 exit ! interface lo ip address 10.0.0.3/32 ip router isis 1515 isis circuit-type level-2-only isis passive mpls enable exit ! interface bp_45 ip address 10.2.0.6/30 ip router isis 1515 isis circuit-type level-2-only mpls enable exit ! interface bp_47 ip address 10.2.0.9/30 ip router isis 1515 isis circuit-type level-2-only mpls enable exit ! interface bp_49 ip address 10.2.0.14/30 ip router isis 1515 isis circuit-type level-2-only mpls enable exit ! interface 28 ip address 172.16.21.1/24 exit ! interface ifcfg-eno2.904 exit ! interface eno2.904 exit ! router bgp 10808 bgp router-id 10.0.0.3 no bgp network import-check neighbor 10.0.0.2 remote-as 10808 neighbor 10.0.0.2 update-source 10.0.0.3 neighbor 10.0.0.4 remote-as 10808 neighbor 10.0.0.4 update-source 10.0.0.3 neighbor 10.0.0.5 remote-as 10808 neighbor 10.0.0.5 update-source 10.0.0.3 ! address-family ipv4 unicast neighbor 10.0.0.2 route-reflector-client neighbor 10.0.0.4 route-reflector-client neighbor 10.0.0.5 route-reflector-client exit-address-family ! address-family ipv4 vpn neighbor 10.0.0.2 activate neighbor 10.0.0.2 route-reflector-client neighbor 10.0.0.4 activate neighbor 10.0.0.4 route-reflector-client neighbor 10.0.0.5 activate neighbor 10.0.0.5 route-reflector-client exit-address-family exit ! router bgp 10808 vrf vrf-14 no bgp ebgp-requires-policy no bgp network import-check neighbor 172.16.21.5 remote-as 1010 neighbor 172.16.21.5 bfd neighbor 172.16.21.5 update-source 28 ! address-family ipv4 unicast redistribute connected redistribute static label vpn export auto rd vpn export 137260:36 rt vpn both 137260:36 export vpn import vpn exit-address-family exit ! mpls ldp router-id 10.0.0.3 neighbor 10.0.0.2 session holdtime 15 neighbor 10.0.0.2 ttl-security disable neighbor 10.0.0.2 password Sherry0808 neighbor 10.0.0.4 session holdtime 15 neighbor 10.0.0.4 ttl-security disable neighbor 10.0.0.4 password Sherry0808 neighbor 10.0.0.5 session holdtime 15 neighbor 10.0.0.5 ttl-security disable neighbor 10.0.0.5 password Sherry0808 ! address-family ipv4 discovery transport-address 10.0.0.3 label local allocate host-routes ! interface bp_45 exit ! interface bp_47 exit ! interface bp_49 exit ! exit-address-family ! exit ! router isis 1515 is-type level-2-only net 39.0000.0128.0100.0000.0003.00 exit ! bfd peer 172.16.21.5 local-address 172.16.21.1 vrf vrf-14 transmit-interval 500 receive-interval 500 exit ! exit ! end

#The above is the configuration on my device with the IP address 172.16.21.1. Can you analyze the reason based on this configuration?

[beith12]

Can we see the output of the following from the three PE devices (with addressing 172.16.19.1, 172.16.20.1, and 172.16.21.1)?

#show ip bgp vrf vrf-14 #show bgp ipv4 vpn #show mpls table #show isis route #show ldp interface

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