Posted on May 27, 2021 9:38 am
 |  Asked by Sebastian Humer
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Hello i hope this is the right place to ask my question(s). And please be gentle my understanding of networks is growing but still really limited. I hope someone has a few minutes and is willing to help me speed up this journey.

Quick pre story. We operate 2 7150s-24 in a Broadcast truck to get a redundent fiber network for our LAWO v_line products. They use a 2 vlan enviroment where each vlan ran through one of the switches to operate redundent. So we decided, because we dont really use 24 ports, to split one of the switches into 2 different vlans or basicly that we have one switch operate like two seperate and have the other switch for a 2nd truck where the task will be exactly the same. I’m now working and learning about the eos and i figured i probably need a little help since this whole thing is quite overwhelming.
Since LAWO recomended these switches and they also gave a simple setup instruction to operate them properly. These were made once on each switch and since them operated without any problems.

run hostname arista7150
username admin secret admin
interface management 1
ip address
interface Vlan 1
ip address
ip igmp snooping
ip igmp snooping vlan 1
ip igmp snooping report-flooding
ip igmp snooping vlan 1 report-flooding
ip igmp snooping report-flooding switch-port Ethernet 1-22
ip igmp snooping querier
ip igmp snooping vlan 1 querier
ip igmp snooping querier address
ip igmp snooping vlan 1 querier address
ip igmp snooping querier version 2
ip igmp snooping vlan 1 querier version 2
ip igmp snooping querier query-interval 30
ip igmp snooping vlan 1 querier query-interval 30
no ip igmp snooping vlan 1 immediate-leave
ptp mode p2ptransparent
ptp source ip
interface Ethernet 1-24
ptp enable

I thought it would be quite easy (and probably is for someone in the networking field) to take these settings and apply them to 2 different vlans and thats what i tried and got kinda working but i still have problems with the ptp clock not working and i guess i’m missing a view variables which i havent thought of.
I’ve put a show run output in the attached textfile that you can see what i got so far.

And by the way network security is not an issue since those networks are fully isolated from the evil internet.

Thank you in advance :)

Posted by Gerard Phillips
Answered on May 27, 2021 10:10 am

Hi Sebastian,

Its certainly possible to do what you are suggesting - running both halves of the -7 network in the same physical switch - but remember that you now have a single point of failure....

Looking at the config, I wonder if the PTP problem is related to routing multicast between the two vlans? From your post, its not clear whether you have 1 or 2 GM's.

The use of transparent clock means that the PTP messages are forwarded as normal multicast, so if they ingress on vlan2, but you need them on vlan3, then they will need to be routed to vlan3.

If this is the issue (single GM), then perhaps the easiest solution is to switch to Boundary Clock mode? This will not need any multicast routing to be enabled. You can find lots of config details in the M&E PTP White paper:

But an example of how to configure the switch for boundary clock would look something like this: (you will need to adapt for your PTP domain settings, message rates and the PTP Priority1 settings)

! Global config
ptp domain 127
ptp priority1 40
ptp priority2 2
ptp mode boundary

! GM facing port
description GM Facing Port
switchport access vlan 2
ptp enable
ptp sync-message interval -3
ptp announce interval 0
ptp delay-req interval -3

! Host facing ports
description Host Facing Port
switchport access vlan 3
ptp enable
ptp sync-message interval -3
ptp announce interval 0
ptp delay-req interval -3
ptp role master

I hope this is useful.



Posted by Philippe Bureau
Answered on May 27, 2021 1:49 pm


I cannot see where your PTP Grand Master (GM) is connected.

You are running the switch in transparent mode but have defined a PTP source (ptp source ip).  Do you want the endpoints to sync directly with the GM or are you expecting the switch to serve PTP to the end devices.  If later, you need to change the ptp to a boundary clock (ptp mode boundary)

You also need to define your ptp domain.

if you configure the switch in boundary mode, you should make sure your ptp annouce intervals and timeouts match your GM and end devices.

You should read this whitepaper, it will help you understand the configuration specific for broadcasting environments.

I would also highly recommend to upgrade to the latest EOS supporting the 7150S platform (EOS at the moment)

Thank you

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