I expect someone like Perry Whittle will answer this in more detail, but when Server-1 goes down, your Subscriber databases(s) on Server-3 will no longer receive transactions (or snapshots - you didn't state what type of replication you are using).

You then have a choice of either bringing the failed Server-1 back up (once you've fixed whatever problem caused it to go down) and replication should continue from where it left off, provided that your Subscription expiry period has not been breached (in which case you'll need to Reinitialise the Subscription)...or...you can set up Replication afresh on Server-2.

Bear in mind that if you choose the second option and you want to create the Subscriptions on Server-3 with exactly the same names as before, you'll need to drop the original subscriptions first.

Regards

Lempster