topic Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION in General Network Management

CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

abhijit_roy — Wed, 03 Feb 2021 21:21:23 GMT

Hi Team,

Kindly suggest regarding following practical case If I connect a p.c/laptop with 10/100 lan card capacity to a 1 gbps port switch port congestion/packet drop might happen???

My switch is X440G2-48p-10G4

Thanks in advance

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

Miguel-Angel_RO — Thu, 04 Feb 2021 00:09:56 GMT

Roy,

It seems normal to me to have packet drops. The device on the other side is probably sending a data flow at Gbps speed.

The TCP layer should be able to handle that. If you use UDP, packets are lost.

If you want to releave it a little bit you can enable flow control on the port (if the X440G2 support it, I don’t know).

Mig

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

abhijit_roy — Thu, 04 Feb 2021 20:25:16 GMT

Thanks for your response, can u please explain following line it is not cleared to me,

“The TCP layer should be able to handle that. If you use UDP, packets are lost”

My use case as follows,

I have LAN Port of 1gbps each, for scarcity of port we have shared that port by using ip phone with one connection to phone and other connection to p.c(ip phone have 2 lan ports), and that phone have 10/100 capacity of each port only, so voice+data both are routed to the 10/100 i guess, and i used “show ports congestion” to monitor packet drops, and found incremental counter, that’s why my confusion is is it due to 10/100 connected to 1 gbps port?? or something else for increasing packet drop counters.

Thanks

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

Miguel-Angel_RO — Fri, 05 Feb 2021 02:08:39 GMT

Roy,

The TCP stack should handle the packet losses resending the packets unacknowledged.

The UDP stack hasn’t acknowledge mechanism.

Is there some common questions in the article here?:

Mig

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

abhijit_roy — Sat, 06 Feb 2021 00:58:52 GMT

is there any alternate way to find out exact error, means device end/switch end, as i have observed that apart from 10/100 to gbps, several times we faced port congestion issue even in 1 to 1 gbps, and in all the cases “show ports flow-control” and “show ports congestion” shows pause Rcvs as well as Packet drops, any commands or naything else

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

Miguel-Angel_RO — Sat, 06 Feb 2021 01:54:43 GMT

Roy,

This analysis domain is quite tricky because the impacted devices are not necessarily the triggers of the packet drops.

For this you need specific devices to analyze the network traffic.

Extreme Application Analytics can be a good starting point.
Fluke Optiview is an example of dedicated device but it has his cost…

Mig

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

abhijit_roy — Sat, 06 Feb 2021 18:51:17 GMT

how to properly enable flow control in this case to get some relive

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

Miguel-Angel_RO — Sat, 06 Feb 2021 18:54:49 GMT

Roy,

In this case check the status before to see if it is activated or not.

Commands disable it are mentioned in the following post:

show / enable / disable have to be used with the arguments.

Mig

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

abhijit_roy — Sun, 07 Feb 2021 00:13:40 GMT

Flow Control: Rx-Pause: Enabled Tx-Pause: Disabled

Above is my each port status, kindly suggest what should I do to minimise packet drops, should I disable both against all ports or enable to minimise packet drops, or just disabled/enable this against one port for testing purpose, is their any negative affect on switch for disabling flow control?

Thnx

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

Miguel-Angel_RO — Sun, 07 Feb 2021 00:17:47 GMT

Roy,

I think you should test the different settings because the behavior can be different depending on the specific environment and devices.

There is no negative effect on the switch. The only impact is to drop more or less packets on the device interface.

Mig

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

abhijit_roy — Sun, 07 Feb 2021 01:09:40 GMT

can u please brief possible reasons of packet drops apart from this speed mismatch. my environment is as follows.

single vlan in each switch with several sub-vlan+aruba wifi in network, with normal p.c+laptop in the end user, that’s it

and cables are are not faulty that’s i can say.

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

Miguel-Angel_RO — Sun, 07 Feb 2021 01:37:09 GMT

Roy,

main reasons for packet drops are

wrong vlan configuration (dropping vlan packets not configured on both sides)
wrong subnet configuration (too big subnet for the type of traffic)
bandwidth congestion (QoS queuing incorrectly sized)
cabling issue
network attack or broadcast storm

A 100Mbps IP Phone with a PC connected on it will be very sensitive to all of this.

Mig

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

abhijit_roy — Sun, 07 Feb 2021 14:05:49 GMT

I was thinking if i can isolate those ip phones to a separate sub-vlan and reduce the port speed of the switch(will be shared to a 10/100 16 ports normal switch) to 100 mbps, as my switch is 10/100/1000, am i thinking in correct way?

means if i use this command

configure ports 1 auto on speed 100 duplex full

Re: CONNECT 100MBPS DEVICE TO 1GBPS SWITCH PORT CONGESTION

Miguel-Angel_RO — Tue, 09 Feb 2021 05:08:00 GMT

Roy,

I would put QoS in place to ensure that voip has priority over the PC.

Whatever the switch/port/settings, the PC will always be in competition with the Phone.

Mig