Hello, I’m a bit new to Arista but I have 1 in my environment I work with. For a long time we had a single Arista switch running a set of hosts. Recently we procured a second one to add in HA with MLAGs. I am going through the planning to add the new switch and hoping to avoid any outages but from what I tell theres really no way around an outage.
So currently we have a compute system connected in a LAG on port-channel 1 via 2 of its 40gb ports.
We have LAG on port-channel 2 to our SAN switches that the compute system uses via 2 10gb ports.
We have a LAG on port-channel 3 to another pair of switches that provide our connection to the firewall via 2 10gb ports.
Finally we have 2 ports going to a pair of F5 load balancers which are not lagged.
This is on a single Arista 7050 switch.
Now I understand the concept and work to form the MLAGs and peer links between the switches, but when I go to form say a new set of MLAGs on port-channel 20 with 2 net new 10gb ports 1 per Arista, for the SAN switches and leave the current LAGs up. STP is going to kick in a block one of the M/LAGs to the SAN switches. If I set it up so it blocks the MLAG and keeps the existing LAG going I’ll still have a brief outage when I shutdown the old LAG on the single Arista and no shut the MLAG from the 2 Aristas to the SAN switches. The same goes for my connection out to the firewall. Is there any way around this outage or am I at the mercy of STP here?
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