Switching

I am attempting to use MSTP to help with some load balancing and redudancy. I have two cisco access switches that feed into two EX4300 distrobution switches. If there is a better way to manage this please fee free to sugest this.

I would like to split off traffic by VLANs but still have the second EX switch in place for redundancy.  At this time the traffic is being re-routed in a simulated failure situation, but when all devices are working the Ciscos appear to be sending all traffic, regardless of VLAN to only one of the two Ex4300.  The closest documentation for this I've found is for 2 Cisco and 1 Juniper (page 12 http://www.juniper.net/us/en/local/pdf/implementation-guides/8010002-en.pdf).  When I look at the spanning tree on the Juniper switchs the correct switch is root for the correct MSTI/VLAN group. When I look at the spanning tree in the Cisco, all MST instances/ VLANs are tagged to the same juniper switch, leaving the other switch in standby.

As the real system has more VLANS and additional access cisco switchs, I have simplified this as an example. Not all VLANS in the ranges indicated are in use or part of the trunk ports either. There is no VLAN-1 in use on the network.

Simplefied line diagram:

                           |--------   EX4300-1  (traffic for VLANs 1-9) 

Cisco Switch --|                                                       |        (tunked connection between junipers)

                           |--------   EX4300-2  (traffice for VLAN 10-19)

Protocols Config from EX4300-1

protocols {
    lldp {
        interface all;
    }
    lldp-med {
        interface all;
    }
    igmp-snooping {
        vlan default;
    }
    mstp {
        configuration-name region1;
        bridge-priority 28k;
        interface left1 {
            mode point-to-point;
        }
        interface left2 {
            mode point-to-point;
        }
        msti 1 {
            bridge-priority 24k;
            vlan 1-9;
        }
        msti 2 {
            bridge-priority 28k;
            vlan 10-19;
        }
    }
}

Protocols Config from EX4300-2

protocols {
    lldp {
        interface all;
    }
    lldp-med {
        interface all;
    }
    igmp-snooping {
        vlan default;
    }
    mstp {
        configuration-name region1;
        bridge-priority 28k;
        interface left1 {
            mode point-to-point;
        }
        interface left2 {
            mode point-to-point;
        }
        msti 1 {
            bridge-priority 28k;
            vlan 1-9;
        }
        msti 2 {
            bridge-priority 24k;
            vlan 10-19;
        }
    }
}

Cisco spanning-tree Config

spanning-tree mode mst
spanning-tree extend system-id
spanning-tree pathcost method long
!
spanning-tree mst configuration
 instance 1 vlan 1-9
 instance 2 vlan 10-19

I did not read your whole [long] text, BUT I believe the better way to to this is to get rid of STP altogeather.  STP based designs went away 10 years ago.  Or at least 5+ -;)

Instead take the 2 x EX4300, make them into a VC.  Now these switches act as 1.  Then create FEC from any of your Cisco access switches with the links split between the 2 x EX4300.  On the EX4300 you just create an AE (LAG) with a member physically residing on each switch.  Then you get completely redundnancy and active-active forwarding on all links of the LAG/FEC, without the need for any messy STP configuration of any type.

Welcome to 2016 and better way to design networks!

Thanks for the sugestion @rccpgm,

A Juniper VC was pitched during the design process. I was tasked with trying and see if this design would function as well. I wanted to make sure I exaused all avanues befor reporting on my findings, and recomeneding the virtual chassi approch.

Its better to have the 2 EX4300 under Virtual Chassis environment and make it logically behaving like one for the Cisco access switch. 

If you start your environment with MSTP and in future if you need to have more VLANs, you need to add more MSTP instance or re-configure the existing. I would request you to put your effort in make the device as VC and start testing from that. 

If you still need to test this scenario, i can lab it up with Juniper as Distribution and Access switch and come to you with solution, because STP with same brand works as expected, with different brand, it will require lots of trail and error as well as research.

Go with Virtual Chassis 🙂

Thanks

Arul