Hi could you please help me on following (very sorry about my english).
Kindly refer attached network topology.
currently we are in the process of implementing our DR Datacenter, (our DR site is installed on local internet service provider (ISP) premises)
ISP will give rack space, power and internet connections (30 Mbps leased line) on their managed DC Rack.
ISP given two link (from different switch, cisco nexus 7k) for leased line for redundancy. we don't have any idea /management access about ISP DC internal network.
Our DC architecure (Company DC portion), Two External switches on stack, two firewall (active /passive), two LAN switches on stack.
Cisco 3650 (Denali 16.3.6) using as External /LAN Switches.
ISP given two link (one link connected to External sw-01 and other connected to external sw-02) with VLAN ID: 789, As per them ISP link connected port on External switch should be access, tag vlan 789 (port bundling not configured).
Firewall configured as Active /Passive, for wan interface two link is bundled as redundant link (active /backup, so switch side no ether-channeling). on firewall wan link we allow ISP network (Vlan 789) and external switch management vlan (vlan 225) same thing on switch side (so external switch port: 2,3 as trunk).
Firewall LAN connected to LAN Switch (as per diagram) only one Vlan is allowed so access mode.
VMWare Host is connected to both LAN switches with etherchannel configured on link.
LAN Switch acting as Layer 3 (intervlan routing is performed).
if any redundant link or device is Powered OFF traffic is shifted to backup link /device with one or two packet drops.
As Part of Failover /Redundancy Testing, we have noticed following.
1. Suppose ISP-02 link (on Ext sw-02 Port: 1) is disconnected, when we reconnect the cable we are facing packet drops (8 packets) to internet /remote Branches connected over VPN after that getting continuous connection without drops. same thing happen during when ISP-01 link re-connection.
2. if Ext Sw-01 if OFF all traffic is routed through Ext Sw-02, after powered ON Ext Sw-01 we are getting continuous packet drops (8 packet) to internet /remote branches, then continuous connection without drops as like point no: 1, same thing when Ext Sw-02 Powered ON.
3. (like point no:2), packet drops (maximum 13 packets) happening if internal LAN switch (any one) Powered ON.
from above we concluded as these continuous packet drops (8 packets) occurred when STP reconvergance happened due to topology changes (redundant link connection/ redundant switch powered ON).
All switches (LAN and External) running RSTP (per vlan) version of STP and all link Is Desg FWD state and Type is P2P. we don't know which version is running on ISP switches (Nexus 7k).
and External Switch Stack is acting as Root bridge (External switch and ISP Nexus switch segment).
Query:
A: is our observation (packet drops at the time of STP reconvergance) is correct or not.
B: if yes, can we reduce the packet drops count (currently maximum 8 packets).
