Why I have higher ping to the VLAN interface than to other local interfacesip f 067 Rrg HO
I wouldn't call it an issue, but I'm curious. On our Quanta switch we have a couple of VLANs and vlan interfaces accordingly.
Let's say I'm on a computer in VLAN 10, if I do:
ping 192.168.10.1
with 192.168.10.1 being the VLAN 10 interface on the switch which is set as gateway for the devices in that VLAN, I get responses in range from 1 ms to (sometimes) 28 ms, or even 50 ms etc. If I ping any other device on the LAN I get responses in less than a millisecond.
Same goes if I go with
traceroute www.stackexchange.com
Here, from the first three hops I get highest delay from my VLAN interface:
gateway (192.168.10.1) 1.601 ms 2.401 ms 2.884 ms
192.168.xx.xx (192.168.xx.xx) 0.714 ms 0.710 ms 0.749 ms
xx.xx.xx.xx (xx.xx.xx.xx) 0.185 ms 0.224 ms 0.220 ms
Can you give me some ideas about that?
-
1The latency measured by ping is the ICMP latency (including processing of the ICMP messages). ICMP is very low on the priority list for a network device. The primary job of a router is to route, and of a switch to switch, and they get around to processing ICMP messages as they have time. You do not want a router or switch to drop traffic while it processes ICMP messages, so routing/switching take precedence, and ICMP is handled as a very low priority, which is why you may see timeouts from network devices because the reply can take too long from the perspective of the host sending the request. – Ron Maupin♦ 7 hours ago
1 Answer
A "L3 switch" will perform the actual packet forwarding (both L2 and L3) using dedicated hardware, but exceptional cases like sending a ping reply or a time exceeded message are normally handled in software by the switch's CPU.
Depending on how powerful and busy the CPU is and how the switch vendor decided to prioritize it's different tasks it may take the CPU some time to get around to processing your packet.
