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SLX not forwarding IPv6 UDP Traffic

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TitleSLX not forwarding IPv6 UDP Traffic
Symptoms
  • IPv6 PING to SLX is successful
[root@CentOS7 ~]# ping -6 2603:b000:0:16::3
PING 2603:b000:0:16::3(2603:b000:0:16::3) 56 data bytes
64 bytes from 2603:b000:0:16::3: icmp_seq=1 ttl=64 time=0.768 ms
64 bytes from 2603:b000:0:16::3: icmp_seq=2 ttl=64 time=0.636 ms
64 bytes from 2603:b000:0:16::3: icmp_seq=3 ttl=64 time=0.539 ms
64 bytes from 2603:b000:0:16::3: icmp_seq=4 ttl=64 time=0.739 ms
64 bytes from 2603:b000:0:16::3: icmp_seq=5 ttl=64 time=0.679 ms
--- 2603:b000:0:16::3 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3001ms
rtt min/avg/max/mdev = 0.539/0.670/0.768/0.094 ms
  • IPv6 Traceroute using ICMP and TCP to SLX is successful
[root@CentOS7 ~]# traceroute -6 -I 2603:b000:0:16::3
traceroute to 2603:b000:0:16::3 (2603:b000:0:16::3), 30 hops max, 80 byte packets
 1  2603:b000:0:16::3 (2603:b000:0:16::3)  0.487 ms  0.538 ms  0.593 ms

SLX ICMP: 
20:02:20.398697 IP6 (hlim 1, next-header ICMPv6 (58) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532 > 2603:b000:0:16::3: [icmp6 sum ok] ICMP6, echo request, seq 1
20:02:20.398739 IP6 (hlim 64, next-header ICMPv6 (58) payload length: 40) 2603:b000:0:16::3 > 2603:b000:0:16:20c:29ff:fefc:1532: [icmp6 sum ok] ICMP6, echo reply, seq 1
20:02:20.398788 IP6 (hlim 1, next-header ICMPv6 (58) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532 > 2603:b000:0:16::3: [icmp6 sum ok] ICMP6, echo request, seq 2
20:02:20.398799 IP6 (hlim 64, next-header ICMPv6 (58) payload length: 40) 2603:b000:0:16::3 > 2603:b000:0:16:20c:29ff:fefc:1532: [icmp6 sum ok] ICMP6, echo reply, seq 2
 
[root@CentOS7 ~]# traceroute -6 -T 2603:b000:0:16::3
traceroute to 2603:b000:0:16::3 (2603:b000:0:16::3), 30 hops max, 80 byte packets
 1  2603:b000:0:16::3 (2603:b000:0:16::3)  0.551 ms  0.588 ms  0.595 ms

SLX TCP:
20:02:30.481873 IP6 (hlim 1, next-header TCP (6) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.34935 > 2603:b000:0:16::3.http: Flags [S], cksum 0xb342 (correct), seq 3982020491, win 5760, options [mss 1440,sackOK,TS val 281951084 ecr 0,nop,wscale 2], length 0
20:02:30.481914 IP6 (hlim 64, next-header TCP (6) payload length: 40) 2603:b000:0:16::3.http > 2603:b000:0:16:20c:29ff:fefc:1532.34935: Flags [S.], cksum 0xfac0 (correct), seq 837265738, ack 3982020492, win 18244, options [mss 9134,sackOK,TS val 246448055 ecr 281951084,nop,wscale 7], length 0
20:02:30.481977 IP6 (hlim 1, next-header TCP (6) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.47060 > 2603:b000:0:16::3.http: Flags [S], cksum 0x0b89 (correct), seq 1196617198, win 5760, options [mss 1440,sackOK,TS val 281951084 ecr 0,nop,wscale 2], length 0
20:02:30.482000 IP6 (hlim 64, next-header TCP (6) payload length: 40) 2603:b000:0:16::3.http > 2603:b000:0:16:20c:29ff:fefc:1532.47060: Flags [S.], cksum 0x0d9d (correct), seq 827060048, ack 1196617199, win 18244, options [mss 9134,sackOK,TS val 246448055 ecr 281951084,nop,wscale 7], length 0
  • IPv6 Traceroute using UDP to SLX Fails (No reply from SLX)
[root@CentOS7 ~]# traceroute -6 -U 2603:b000:0:16::3
traceroute to 2603:b000:0:16::3 (2603:b000:0:16::3), 30 hops max, 80 byte packets
 1  * * *
 2  * * *
 3  * * *

SLX UDP:
20:02:56.056451 IP6 (hlim 22, next-header UDP (17) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.58194 > 2603:b000:0:16::3.domain: [udp sum ok] 16449 op8 [b2&3=0x4243] [17991a] [17477q] [18505n] [19019au][|domain]
20:02:56.056535 IP6 (hlim 22, next-header UDP (17) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.40742 > 2603:b000:0:16::3.domain: [udp sum ok] 16449 op8 [b2&3=0x4243] [17991a] [17477q] [18505n] [19019au][|domain]
20:02:56.056569 IP6 (hlim 23, next-header UDP (17) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.47722 > 2603:b000:0:16::3.domain: [udp sum ok] 16449 op8 [b2&3=0x4243] [17991a] [17477q] [18505n] [19019au][|domain]
20:02:56.056598 IP6 (hlim 23, next-header UDP (17) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.56065 > 2603:b000:0:16::3.domain: [udp sum ok] 16449 op8 [b2&3=0x4243] [17991a] [17477q] [18505n] [19019au][|domain]
  • IPv6 Traceroute using UDP to device connected to SLX (transit) is successful (default TCAM Profile only)
[root@CentOS7 ~]# traceroute -U 2604:b000:0:16::2
traceroute to 2604:b000:0:16::2 (2604:b000:0:16::2), 30 hops max, 80 byte packets
 1  2603:b000:0:16::3 (2603:b000:0:16::3)  1.258 ms  1.729 ms  2.227 ms
 2  2604:b000:0:16::2 (2604:b000:0:16::2)  0.293 ms * *

root@CentOS7 ~]# traceroute -U 2604:b000:0:16::2
traceroute to 2604:b000:0:16::2 (2604:b000:0:16::2), 30 hops max, 80 byte packets
 1  2603:b000:0:16::3 (2603:b000:0:16::3)  1.258 ms  1.729 ms  2.227 ms
 2  2604:b000:0:16::2 (2604:b000:0:16::2)  0.293 ms * *
 
21:07:29.179268 IP6 (hlim 1, next-header UDP (17) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.38690 > 2604:b000:0:16::2.domain: [udp sum ok] 16449 op8 [b2&3=0x4243] [17991a] [17477q] [18505n] [19019au][|domain]
21:07:29.180093 IP6 (hlim 64, next-header ICMPv6 (58) payload length: 88) 2603:b000:0:16::3 > 2603:b000:0:16:20c:29ff:fefc:1532: [icmp6 sum ok] ICMP6, time exceeded in-transit for 2604:b000:0:16::2
21:07:29.180164 IP6 (hlim 1, next-header UDP (17) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.52457 > 2604:b000:0:16::2.domain: [udp sum ok] 16449 op8 [b2&3=0x4243] [17991a] [17477q] [18505n] [19019au][|domain]
21:07:29.180651 IP6 (hlim 64, next-header ICMPv6 (58) payload length: 88) 2603:b000:0:16::3 > 2603:b000:0:16:20c:29ff:fefc:1532: [icmp6 sum ok] ICMP6, time exceeded in-transit for 2604:b000:0:16::2
21:07:29.180685 IP6 (hlim 1, next-header UDP (17) payload length: 40) 2603:b000:0:16:20c:29ff:fefc:1532.58535 > 2604:b000:0:16::2.domain: [udp sum ok] 16449 op8 [b2&3=0x4243] [17991a] [17477q] [18505n] [19019au][|domain]
21:07:29.181174 IP6 (hlim 64, next-header ICMPv6 (58) payload length: 88) 2603:b000:0:16::3 > 2603:b000:0:16:20c:29ff:fefc:1532: [icmp6 sum ok] ICMP6, time exceeded in-transit for 2604:b000:0:16::2


 
Environment
  • SLX Hardware (all)
  • SLXOS 17r/s, 18r/s
Cause
1.) SLX is failing to forward UDP Packets from L2 to the L3 stack resulting in no response
2.) TCAM Profile "layer2-optimized-1" is failing to transmit IPv6 UDP Traffic
Resolution
IF USING THE DEFALUT TCAM PROFILE:
  • Configure Ethernet interface to use "ipv6 icmpv6 unreachable" command
  • Command is not available on VE interfaces
  • VE support is available in 20.1.1 and 18r.2.0c
IF USING THE "layer2-optimized-1" TCAM PROFILE:
  • Switch to Default TCAM Profile
  • Upgrade to SLXOS 20.1.1
    • In order to upgrade it is required you switch to the Default TCAM Profile
    • Upgrades to the Broadcom SDK resulted in the Layer2-Optimized profile being merged into the Default Profile
    • Once you have upgraded, IPv6 UDP Traffic will transit the SLX with no issues
    • For IPv6 UDP traceroutes to return use the "ipv6 icmpv6 unreachable" on your VE or Ethernet interface
Additional notes

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