Loss of fragmented traffic

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1

Hello!

We’re running VyOS on 2 Supermicro servers. And see a lot of losses of fragmented traffic on servers. Even ping between 2 servers with a size larger than MTU does not pass. Has anyone encountered a similar problem.

2

Definitely. Many times. Are you running a VPN between these two vyos-Supermicros? If so, what VPN technology?

3

No, I’m not running VPN. Simple scheme: Router 1 (eth1) - (eth1) Router 2

R1: show int ethernet eth1
address 172.20.20.1/24
duplex auto
hw-id ac:1f:6b:6d:12:59
smp-affinity auto
speed auto

R2: show int ethernet eth1
address 172.20.20.2/24
duplex auto
hw-id ac:1f:6b:6d:12:59
smp-affinity auto
speed auto

R2: ping 172.20.20.1 size 1472
PING 172.20.20.1 (172.20.20.1) 1472(1500) bytes of data.
1480 bytes from 172.20.20.1: icmp_seq=1 ttl=64 time=0.216 ms
1480 bytes from 172.20.20.1: icmp_seq=2 ttl=64 time=0.164 ms

R2: ping 172.20.20.1 size 1500
PING 172.20.20.1 (172.20.20.1) 1500(1528) bytes of data.
^C
— 172.20.20.1 ping statistics —
4 packets transmitted, 0 received, 100% packet loss, time 3076ms

monitor traffic interface eth1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 262144 bytes
12:54:05.818261 IP 172.20.20.2 > asbr1: ICMP echo request, id 19762, seq 1, length 1480
12:54:05.818277 IP 172.20.20.2 > asbr1: icmp
12:54:06.843944 IP 172.20.20.2 > asbr1: ICMP echo request, id 19762, seq 2, length 1480
12:54:06.843960 IP 172.20.20.2 > asbr1: icmp
12:54:07.871964 IP 172.20.20.2 > asbr1: ICMP echo request, id 19762, seq 3, length 1480
12:54:07.871976 IP 172.20.20.2 > asbr1: icmp
12:54:08.891974 IP 172.20.20.2 > asbr1: ICMP echo request, id 19762, seq 4, length 1480
12:54:08.891988 IP 172.20.20.2 > asbr1: icmp
12:54:09.920008 IP 172.20.20.2 > asbr1: ICMP echo request, id 19762, seq 5, length 1480
12:54:09.920028 IP 172.20.20.2 > asbr1: icmp

No answers!

4

Seems like router does not assemble fragments

5

What is your mtu setting on the link between the two routers?

6

MTU between routers is 1500

7

Hi @lka82, I see the same MAC address on 2 routers, is this copy-paste mistake?

8

Just a mistake:
R1:
ethernet eth1 {
address 172.20.20.1/24
duplex auto
hw-id 00:25:90:bd:35:77
smp-affinity auto
speed auto
}

9

After two days the problem just disappeared. Mystic.