Adding Switch to Lan

[pcromwell]

We have a new switch that we are trying to put in place of an EOL switch.  The switch has about 6 svi's for the vlans. To minimise downtime, we have added the new switch into the lan alongside the old switch and moved the cables over 1 by 1. This has all worked fine. however when I disconnect the old switch. Everything stops working. I can ping devices from the switch svi. but any device to device pings fail, even though they could be on the same vlan. When I plug the old switch back in it all works again.

I have since then added HSRP and tried a higher priority for the new switch but again it fails. I have to have the old switch be the higher priority for the vlans. I did notice that the new switch was running version 1 of vtp whilst the others were version 2, have since changed this.

It's as if the new switch is not communicating with all the other switches. I am sure I am missing something obvious.

Is anyone able to shed some light on this?

[Mark Malone]

only guessing here as cant see config but check spanning-tree is not blocking vlans at layer 2

make sure everything is being forwarded on the trunks no vlans missing or being dropped

check correct default-gateway in place

vtp 1 and 2 are backward compatible so that shouldn't be your issue

but any device to device pings fail, even though they could be on the same vlan

the arp tables are ok for these ips ?  this is across switches yes not on the same switch in same vlan

[pcromwell]

Thanks for the reply Mark, I have noticed the new switch is set to PVST and the legacy switches are using mst. So this is prob my problem. should I just set the new switch to use mst like the others?

[Mark Malone]

yes I wouldn't bother trying to migrate between the stp versions its messy and you should only do it if you have to , just pick one type pvst or mst whatever is supported on both make it easier to maintain , that's maybe your issue something at layer 2 being blocked in stp then between the 2 types